# Source code for _pytest.python

    """ Python test discovery, setup and run of test functions. """
    import re
    import fnmatch
    import functools
    import py
    import inspect
    import sys
    import pytest
    from _pytest.mark import MarkDecorator, MarkerError
    from py._code.code import TerminalRepr

    try:
        import enum
    except ImportError:  # pragma: no cover
        # Only available in Python 3.4+ or as a backport
        enum = None

    import _pytest
    import pluggy

    cutdir2 = py.path.local(_pytest.__file__).dirpath()
    cutdir1 = py.path.local(pluggy.__file__.rstrip("oc"))

    NoneType = type(None)
    NOTSET = object()
    isfunction = inspect.isfunction
    isclass = inspect.isclass
    callable = py.builtin.callable
    # used to work around a python2 exception info leak
    exc_clear = getattr(sys, 'exc_clear', lambda: None)
    # The type of re.compile objects is not exposed in Python.
    REGEX_TYPE = type(re.compile(''))

    def filter_traceback(entry):
        return entry.path != cutdir1 and not entry.path.relto(cutdir2)

    def get_real_func(obj):
        """ gets the real function object of the (possibly) wrapped object by
        functools.wraps or functools.partial.
        """
        while hasattr(obj, "__wrapped__"):
            obj = obj.__wrapped__
        if isinstance(obj, functools.partial):
            obj = obj.func
        return obj

    def getfslineno(obj):
        # xxx let decorators etc specify a sane ordering
        obj = get_real_func(obj)
        if hasattr(obj, 'place_as'):
            obj = obj.place_as
        fslineno = py.code.getfslineno(obj)
        assert isinstance(fslineno[1], int), obj
        return fslineno

    def getimfunc(func):
        try:
            return func.__func__
        except AttributeError:
            try:
                return func.im_func
            except AttributeError:
                return func

    def safe_getattr(object, name, default):
        """ Like getattr but return default upon any Exception.

        Attribute access can potentially fail for 'evil' Python objects.
        See issue214
        """
        try:
            return getattr(object, name, default)
        except Exception:
            return default

    class FixtureFunctionMarker:
        def __init__(self, scope, params,
                     autouse=False, yieldctx=False, ids=None):
            self.scope = scope
            self.params = params
            self.autouse = autouse
            self.yieldctx = yieldctx
            self.ids = ids

        def __call__(self, function):
            if isclass(function):
                raise ValueError(
                        "class fixtures not supported (may be in the future)")
            function._pytestfixturefunction = self
            return function

    def fixture(scope="function", params=None, autouse=False, ids=None):
        """ (return a) decorator to mark a fixture factory function.

        This decorator can be used (with or or without parameters) to define
        a fixture function.  The name of the fixture function can later be
        referenced to cause its invocation ahead of running tests: test
        modules or classes can use the pytest.mark.usefixtures(fixturename)
        marker.  Test functions can directly use fixture names as input
        arguments in which case the fixture instance returned from the fixture
        function will be injected.

        :arg scope: the scope for which this fixture is shared, one of
                    "function" (default), "class", "module", "session".

        :arg params: an optional list of parameters which will cause multiple
                    invocations of the fixture function and all of the tests
                    using it.

        :arg autouse: if True, the fixture func is activated for all tests that
                    can see it.  If False (the default) then an explicit
                    reference is needed to activate the fixture.

        :arg ids: list of string ids each corresponding to the params
           so that they are part of the test id. If no ids are provided
           they will be generated automatically from the params.

        """
        if callable(scope) and params is None and autouse == False:
            # direct decoration
            return FixtureFunctionMarker(
                    "function", params, autouse)(scope)
        if params is not None and not isinstance(params, (list, tuple)):
            params = list(params)
        return FixtureFunctionMarker(scope, params, autouse, ids=ids)

    def yield_fixture(scope="function", params=None, autouse=False, ids=None):
        """ (return a) decorator to mark a yield-fixture factory function
        (EXPERIMENTAL).

        This takes the same arguments as :py:func:`pytest.fixture` but
        expects a fixture function to use a ``yield`` instead of a ``return``
        statement to provide a fixture.  See
        http://pytest.org/en/latest/yieldfixture.html for more info.
        """
        if callable(scope) and params is None and autouse == False:
            # direct decoration
            return FixtureFunctionMarker(
                    "function", params, autouse, yieldctx=True)(scope)
        else:
            return FixtureFunctionMarker(scope, params, autouse,
                                         yieldctx=True, ids=ids)

    defaultfuncargprefixmarker = fixture()

    def pyobj_property(name):
        def get(self):
            node = self.getparent(getattr(pytest, name))
            if node is not None:
                return node.obj
        doc = "python %s object this node was collected from (can be None)." % (
              name.lower(),)
        return property(get, None, None, doc)

    def pytest_addoption(parser):
        group = parser.getgroup("general")
        group.addoption('--fixtures', '--funcargs',
                   action="store_true", dest="showfixtures", default=False,
                   help="show available fixtures, sorted by plugin appearance")
        parser.addini("usefixtures", type="args", default=[],
            help="list of default fixtures to be used with this project")
        parser.addini("python_files", type="args",
            default=['test_*.py', '*_test.py'],
            help="glob-style file patterns for Python test module discovery")
        parser.addini("python_classes", type="args", default=["Test",],
            help="prefixes or glob names for Python test class discovery")
        parser.addini("python_functions", type="args", default=["test",],
            help="prefixes or glob names for Python test function and "
                 "method discovery")

    def pytest_cmdline_main(config):
        if config.option.showfixtures:
            showfixtures(config)
            return 0

    def pytest_generate_tests(metafunc):
        # those alternative spellings are common - raise a specific error to alert
        # the user
        alt_spellings = ['parameterize', 'parametrise', 'parameterise']
        for attr in alt_spellings:
            if hasattr(metafunc.function, attr):
                msg = "{0} has '{1}', spelling should be 'parametrize'"
                raise MarkerError(msg.format(metafunc.function.__name__, attr))
        try:
            markers = metafunc.function.parametrize
        except AttributeError:
            return
        for marker in markers:
            metafunc.parametrize(*marker.args, **marker.kwargs)

    def pytest_configure(config):
        config.addinivalue_line("markers",
            "parametrize(argnames, argvalues): call a test function multiple "
            "times passing in different arguments in turn. argvalues generally "
            "needs to be a list of values if argnames specifies only one name "
            "or a list of tuples of values if argnames specifies multiple names. "
            "Example: @parametrize('arg1', [1,2]) would lead to two calls of the "
            "decorated test function, one with arg1=1 and another with arg1=2."
            "see http://pytest.org/latest/parametrize.html for more info and "
            "examples."
        )
        config.addinivalue_line("markers",
            "usefixtures(fixturename1, fixturename2, ...): mark tests as needing "
            "all of the specified fixtures. see http://pytest.org/latest/fixture.html#usefixtures "
        )

    def pytest_sessionstart(session):
        session._fixturemanager = FixtureManager(session)

    @pytest.hookimpl(trylast=True)
    def pytest_namespace():
        raises.Exception = pytest.fail.Exception
        return {
            'fixture': fixture,
            'yield_fixture': yield_fixture,
            'raises' : raises,
            'collect': {
            'Module': Module, 'Class': Class, 'Instance': Instance,
            'Function': Function, 'Generator': Generator,
            '_fillfuncargs': fillfixtures}
        }

    @fixture(scope="session")
    def pytestconfig(request):
        """ the pytest config object with access to command line opts."""
        return request.config

    @pytest.hookimpl(trylast=True)
    def pytest_pyfunc_call(pyfuncitem):
        testfunction = pyfuncitem.obj
        if pyfuncitem._isyieldedfunction():
            testfunction(*pyfuncitem._args)
        else:
            funcargs = pyfuncitem.funcargs
            testargs = {}
            for arg in pyfuncitem._fixtureinfo.argnames:
                testargs[arg] = funcargs[arg]
            testfunction(**testargs)
        return True

    def pytest_collect_file(path, parent):
        ext = path.ext
        if ext == ".py":
            if not parent.session.isinitpath(path):
                for pat in parent.config.getini('python_files'):
                    if path.fnmatch(pat):
                        break
                else:
                   return
            ihook = parent.session.gethookproxy(path)
            return ihook.pytest_pycollect_makemodule(path=path, parent=parent)

    def pytest_pycollect_makemodule(path, parent):
        return Module(path, parent)

    @pytest.hookimpl(hookwrapper=True)
    def pytest_pycollect_makeitem(collector, name, obj):
        outcome = yield
        res = outcome.get_result()
        if res is not None:
            raise StopIteration
        # nothing was collected elsewhere, let's do it here
        if isclass(obj):
            if collector.istestclass(obj, name):
                Class = collector._getcustomclass("Class")
                outcome.force_result(Class(name, parent=collector))
        elif collector.istestfunction(obj, name):
            # mock seems to store unbound methods (issue473), normalize it
            obj = getattr(obj, "__func__", obj)
            if not isfunction(obj):
                collector.warn(code="C2", message=
                    "cannot collect %r because it is not a function."
                    % name, )
            if getattr(obj, "__test__", True):
                if is_generator(obj):
                    res = Generator(name, parent=collector)
                else:
                    res = list(collector._genfunctions(name, obj))
                outcome.force_result(res)

    def is_generator(func):
        try:
            return py.code.getrawcode(func).co_flags & 32 # generator function
        except AttributeError: # builtin functions have no bytecode
            # assume them to not be generators
            return False

    class PyobjContext(object):
        module = pyobj_property("Module")
        cls = pyobj_property("Class")
        instance = pyobj_property("Instance")

    class PyobjMixin(PyobjContext):
        def obj():
            def fget(self):
                try:
                    return self._obj
                except AttributeError:
                    self._obj = obj = self._getobj()
                    return obj
            def fset(self, value):
                self._obj = value
            return property(fget, fset, None, "underlying python object")
        obj = obj()

        def _getobj(self):
            return getattr(self.parent.obj, self.name)

        def getmodpath(self, stopatmodule=True, includemodule=False):
            """ return python path relative to the containing module. """
            chain = self.listchain()
            chain.reverse()
            parts = []
            for node in chain:
                if isinstance(node, Instance):
                    continue
                name = node.name
                if isinstance(node, Module):
                    assert name.endswith(".py")
                    name = name[:-3]
                    if stopatmodule:
                        if includemodule:
                            parts.append(name)
                        break
                parts.append(name)
            parts.reverse()
            s = ".".join(parts)
            return s.replace(".[", "[")

        def _getfslineno(self):
            return getfslineno(self.obj)

        def reportinfo(self):
            # XXX caching?
            obj = self.obj
            if hasattr(obj, 'compat_co_firstlineno'):
                # nose compatibility
                fspath = sys.modules[obj.__module__].__file__
                if fspath.endswith(".pyc"):
                    fspath = fspath[:-1]
                lineno = obj.compat_co_firstlineno
            else:
                fspath, lineno = getfslineno(obj)
            modpath = self.getmodpath()
            assert isinstance(lineno, int)
            return fspath, lineno, modpath

    class PyCollector(PyobjMixin, pytest.Collector):

        def funcnamefilter(self, name):
            return self._matches_prefix_or_glob_option('python_functions', name)

        def isnosetest(self, obj):
            """ Look for the __test__ attribute, which is applied by the
            @nose.tools.istest decorator
            """
            return safe_getattr(obj, '__test__', False)

        def classnamefilter(self, name):
            return self._matches_prefix_or_glob_option('python_classes', name)

        def istestfunction(self, obj, name):
            return (
                (self.funcnamefilter(name) or self.isnosetest(obj))
                and safe_getattr(obj, "__call__", False) and getfixturemarker(obj) is None
            )

        def istestclass(self, obj, name):
            return self.classnamefilter(name) or self.isnosetest(obj)

        def _matches_prefix_or_glob_option(self, option_name, name):
            """
            checks if the given name matches the prefix or glob-pattern defined
            in ini configuration.
            """
            for option in self.config.getini(option_name):
                if name.startswith(option):
                    return True
                # check that name looks like a glob-string before calling fnmatch
                # because this is called for every name in each collected module,
                # and fnmatch is somewhat expensive to call
                elif ('*' in option or '?' in option or '[' in option) and \
                        fnmatch.fnmatch(name, option):
                    return True
            return False

        def collect(self):
            if not getattr(self.obj, "__test__", True):
                return []

            # NB. we avoid random getattrs and peek in the __dict__ instead
            # (XXX originally introduced from a PyPy need, still true?)
            dicts = [getattr(self.obj, '__dict__', {})]
            for basecls in inspect.getmro(self.obj.__class__):
                dicts.append(basecls.__dict__)
            seen = {}
            l = []
            for dic in dicts:
                for name, obj in dic.items():
                    if name in seen:
                        continue
                    seen[name] = True
                    res = self.makeitem(name, obj)
                    if res is None:
                        continue
                    if not isinstance(res, list):
                        res = [res]
                    l.extend(res)
            l.sort(key=lambda item: item.reportinfo()[:2])
            return l

        def makeitem(self, name, obj):
            #assert self.ihook.fspath == self.fspath, self
            return self.ihook.pytest_pycollect_makeitem(
                collector=self, name=name, obj=obj)

        def _genfunctions(self, name, funcobj):
            module = self.getparent(Module).obj
            clscol = self.getparent(Class)
            cls = clscol and clscol.obj or None
            transfer_markers(funcobj, cls, module)
            fm = self.session._fixturemanager
            fixtureinfo = fm.getfixtureinfo(self, funcobj, cls)
            metafunc = Metafunc(funcobj, fixtureinfo, self.config,
                                cls=cls, module=module)
            methods = []
            if hasattr(module, "pytest_generate_tests"):
                methods.append(module.pytest_generate_tests)
            if hasattr(cls, "pytest_generate_tests"):
                methods.append(cls().pytest_generate_tests)
            if methods:
                self.ihook.pytest_generate_tests.call_extra(methods,
                                                            dict(metafunc=metafunc))
            else:
                self.ihook.pytest_generate_tests(metafunc=metafunc)

            Function = self._getcustomclass("Function")
            if not metafunc._calls:
                yield Function(name, parent=self, fixtureinfo=fixtureinfo)
            else:
                # add funcargs() as fixturedefs to fixtureinfo.arg2fixturedefs
                add_funcarg_pseudo_fixture_def(self, metafunc, fm)

                for callspec in metafunc._calls:
                    subname = "%s[%s]" %(name, callspec.id)
                    yield Function(name=subname, parent=self,
                                   callspec=callspec, callobj=funcobj,
                                   fixtureinfo=fixtureinfo,
                                   keywords={callspec.id:True})

    def add_funcarg_pseudo_fixture_def(collector, metafunc, fixturemanager):
        # this function will transform all collected calls to a functions
        # if they use direct funcargs (i.e. direct parametrization)
        # because we want later test execution to be able to rely on
        # an existing FixtureDef structure for all arguments.
        # XXX we can probably avoid this algorithm  if we modify CallSpec2
        # to directly care for creating the fixturedefs within its methods.
        if not metafunc._calls[0].funcargs:
            return # this function call does not have direct parametrization
        # collect funcargs of all callspecs into a list of values
        arg2params = {}
        arg2scope = {}
        for callspec in metafunc._calls:
            for argname, argvalue in callspec.funcargs.items():
                assert argname not in callspec.params
                callspec.params[argname] = argvalue
                arg2params_list = arg2params.setdefault(argname, [])
                callspec.indices[argname] = len(arg2params_list)
                arg2params_list.append(argvalue)
                if argname not in arg2scope:
                    scopenum = callspec._arg2scopenum.get(argname,
                                                          scopenum_function)
                    arg2scope[argname] = scopes[scopenum]
            callspec.funcargs.clear()

        # register artificial FixtureDef's so that later at test execution
        # time we can rely on a proper FixtureDef to exist for fixture setup.
        arg2fixturedefs = metafunc._arg2fixturedefs
        for argname, valuelist in arg2params.items():
            # if we have a scope that is higher than function we need
            # to make sure we only ever create an according fixturedef on
            # a per-scope basis. We thus store and cache the fixturedef on the
            # node related to the scope.
            scope = arg2scope[argname]
            node = None
            if scope != "function":
                node = get_scope_node(collector, scope)
                if node is None:
                    assert scope == "class" and isinstance(collector, Module)
                    # use module-level collector for class-scope (for now)
                    node = collector
            if node and argname in node._name2pseudofixturedef:
                arg2fixturedefs[argname] = [node._name2pseudofixturedef[argname]]
            else:
                fixturedef =  FixtureDef(fixturemanager, '', argname,
                               get_direct_param_fixture_func,
                               arg2scope[argname],
                               valuelist, False, False)
                arg2fixturedefs[argname] = [fixturedef]
                if node is not None:
                    node._name2pseudofixturedef[argname] = fixturedef

    def get_direct_param_fixture_func(request):
        return request.param

    class FuncFixtureInfo:
        def __init__(self, argnames, names_closure, name2fixturedefs):
            self.argnames = argnames
            self.names_closure = names_closure
            self.name2fixturedefs = name2fixturedefs

    def _marked(func, mark):
        """ Returns True if :func: is already marked with :mark:, False otherwise.
        This can happen if marker is applied to class and the test file is
        invoked more than once.
        """
        try:
            func_mark = getattr(func, mark.name)
        except AttributeError:
            return False
        return mark.args == func_mark.args and mark.kwargs == func_mark.kwargs

    def transfer_markers(funcobj, cls, mod):
        # XXX this should rather be code in the mark plugin or the mark
        # plugin should merge with the python plugin.
        for holder in (cls, mod):
            try:
                pytestmark = holder.pytestmark
            except AttributeError:
                continue
            if isinstance(pytestmark, list):
                for mark in pytestmark:
                    if not _marked(funcobj, mark):
                        mark(funcobj)
            else:
                if not _marked(funcobj, pytestmark):
                    pytestmark(funcobj)

    class Module(pytest.File, PyCollector):
        """ Collector for test classes and functions. """
        def _getobj(self):
            return self._memoizedcall('_obj', self._importtestmodule)

        def collect(self):
            self.session._fixturemanager.parsefactories(self)
            return super(Module, self).collect()

        def _importtestmodule(self):
            # we assume we are only called once per module
            try:
                mod = self.fspath.pyimport(ensuresyspath="append")
            except SyntaxError:
                raise self.CollectError(
                    py.code.ExceptionInfo().getrepr(style="short"))
            except self.fspath.ImportMismatchError:
                e = sys.exc_info()[1]
                raise self.CollectError(
                    "import file mismatch:\n"
                    "imported module %r has this __file__ attribute:\n"
                    "  %s\n"
                    "which is not the same as the test file we want to collect:\n"
                    "  %s\n"
                    "HINT: remove __pycache__ / .pyc files and/or use a "
                    "unique basename for your test file modules"
                     % e.args
                )
            #print "imported test module", mod
            self.config.pluginmanager.consider_module(mod)
            return mod

        def setup(self):
            setup_module = xunitsetup(self.obj, "setUpModule")
            if setup_module is None:
                setup_module = xunitsetup(self.obj, "setup_module")
            if setup_module is not None:
                #XXX: nose compat hack, move to nose plugin
                # if it takes a positional arg, its probably a pytest style one
                # so we pass the current module object
                if inspect.getargspec(setup_module)[0]:
                    setup_module(self.obj)
                else:
                    setup_module()
            fin = getattr(self.obj, 'tearDownModule', None)
            if fin is None:
                fin = getattr(self.obj, 'teardown_module', None)
            if fin is not None:
                #XXX: nose compat hack, move to nose plugin
                # if it takes a positional arg, it's probably a pytest style one
                # so we pass the current module object
                if inspect.getargspec(fin)[0]:
                    finalizer = lambda: fin(self.obj)
                else:
                    finalizer = fin
                self.addfinalizer(finalizer)

    class Class(PyCollector):
        """ Collector for test methods. """
        def collect(self):
            if hasinit(self.obj):
                self.warn("C1", "cannot collect test class %r because it has a "
                    "__init__ constructor" % self.obj.__name__)
                return []
            return [self._getcustomclass("Instance")(name="()", parent=self)]

        def setup(self):
            setup_class = xunitsetup(self.obj, 'setup_class')
            if setup_class is not None:
                setup_class = getattr(setup_class, 'im_func', setup_class)
                setup_class = getattr(setup_class, '__func__', setup_class)
                setup_class(self.obj)

            fin_class = getattr(self.obj, 'teardown_class', None)
            if fin_class is not None:
                fin_class = getattr(fin_class, 'im_func', fin_class)
                fin_class = getattr(fin_class, '__func__', fin_class)
                self.addfinalizer(lambda: fin_class(self.obj))

    class Instance(PyCollector):
        def _getobj(self):
            obj = self.parent.obj()
            return obj

        def collect(self):
            self.session._fixturemanager.parsefactories(self)
            return super(Instance, self).collect()

        def newinstance(self):
            self.obj = self._getobj()
            return self.obj

    class FunctionMixin(PyobjMixin):
        """ mixin for the code common to Function and Generator.
        """

        def setup(self):
            """ perform setup for this test function. """
            if hasattr(self, '_preservedparent'):
                obj = self._preservedparent
            elif isinstance(self.parent, Instance):
                obj = self.parent.newinstance()
                self.obj = self._getobj()
            else:
                obj = self.parent.obj
            if inspect.ismethod(self.obj):
                setup_name = 'setup_method'
                teardown_name = 'teardown_method'
            else:
                setup_name = 'setup_function'
                teardown_name = 'teardown_function'
            setup_func_or_method = xunitsetup(obj, setup_name)
            if setup_func_or_method is not None:
                setup_func_or_method(self.obj)
            fin = getattr(obj, teardown_name, None)
            if fin is not None:
                self.addfinalizer(lambda: fin(self.obj))

        def _prunetraceback(self, excinfo):
            if hasattr(self, '_obj') and not self.config.option.fulltrace:
                code = py.code.Code(get_real_func(self.obj))
                path, firstlineno = code.path, code.firstlineno
                traceback = excinfo.traceback
                ntraceback = traceback.cut(path=path, firstlineno=firstlineno)
                if ntraceback == traceback:
                    ntraceback = ntraceback.cut(path=path)
                    if ntraceback == traceback:
                        #ntraceback = ntraceback.cut(excludepath=cutdir2)
                        ntraceback = ntraceback.filter(filter_traceback)
                        if not ntraceback:
                            ntraceback = traceback

                excinfo.traceback = ntraceback.filter()
                # issue364: mark all but first and last frames to
                # only show a single-line message for each frame
                if self.config.option.tbstyle == "auto":
                    if len(excinfo.traceback) > 2:
                        for entry in excinfo.traceback[1:-1]:
                            entry.set_repr_style('short')

        def _repr_failure_py(self, excinfo, style="long"):
            if excinfo.errisinstance(pytest.fail.Exception):
                if not excinfo.value.pytrace:
                    return str(excinfo.value)
            return super(FunctionMixin, self)._repr_failure_py(excinfo,
                style=style)

        def repr_failure(self, excinfo, outerr=None):
            assert outerr is None, "XXX outerr usage is deprecated"
            style = self.config.option.tbstyle
            if style == "auto":
                style = "long"
            return self._repr_failure_py(excinfo, style=style)

    class Generator(FunctionMixin, PyCollector):
        def collect(self):
            # test generators are seen as collectors but they also
            # invoke setup/teardown on popular request
            # (induced by the common "test_*" naming shared with normal tests)
            self.session._setupstate.prepare(self)
            # see FunctionMixin.setup and test_setupstate_is_preserved_134
            self._preservedparent = self.parent.obj
            l = []
            seen = {}
            for i, x in enumerate(self.obj()):
                name, call, args = self.getcallargs(x)
                if not callable(call):
                    raise TypeError("%r yielded non callable test %r" %(self.obj, call,))
                if name is None:
                    name = "[%d]" % i
                else:
                    name = "['%s']" % name
                if name in seen:
                    raise ValueError("%r generated tests with non-unique name %r" %(self, name))
                seen[name] = True
                l.append(self.Function(name, self, args=args, callobj=call))
            return l

        def getcallargs(self, obj):
            if not isinstance(obj, (tuple, list)):
                obj = (obj,)
            # explict naming
            if isinstance(obj[0], py.builtin._basestring):
                name = obj[0]
                obj = obj[1:]
            else:
                name = None
            call, args = obj[0], obj[1:]
            return name, call, args

    def hasinit(obj):
        init = getattr(obj, '__init__', None)
        if init:
            if init != object.__init__:
                return True

    def fillfixtures(function):
        """ fill missing funcargs for a test function. """
        try:
            request = function._request
        except AttributeError:
            # XXX this special code path is only expected to execute
            # with the oejskit plugin.  It uses classes with funcargs
            # and we thus have to work a bit to allow this.
            fm = function.session._fixturemanager
            fi = fm.getfixtureinfo(function.parent, function.obj, None)
            function._fixtureinfo = fi
            request = function._request = FixtureRequest(function)
            request._fillfixtures()
            # prune out funcargs for jstests
            newfuncargs = {}
            for name in fi.argnames:
                newfuncargs[name] = function.funcargs[name]
            function.funcargs = newfuncargs
        else:
            request._fillfixtures()

    _notexists = object()

    class CallSpec2(object):
        def __init__(self, metafunc):
            self.metafunc = metafunc
            self.funcargs = {}
            self._idlist = []
            self.params = {}
            self._globalid = _notexists
            self._globalid_args = set()
            self._globalparam = _notexists
            self._arg2scopenum = {}  # used for sorting parametrized resources
            self.keywords = {}
            self.indices = {}

        def copy(self, metafunc):
            cs = CallSpec2(self.metafunc)
            cs.funcargs.update(self.funcargs)
            cs.params.update(self.params)
            cs.keywords.update(self.keywords)
            cs.indices.update(self.indices)
            cs._arg2scopenum.update(self._arg2scopenum)
            cs._idlist = list(self._idlist)
            cs._globalid = self._globalid
            cs._globalid_args = self._globalid_args
            cs._globalparam = self._globalparam
            return cs

        def _checkargnotcontained(self, arg):
            if arg in self.params or arg in self.funcargs:
                raise ValueError("duplicate %r" %(arg,))

        def getparam(self, name):
            try:
                return self.params[name]
            except KeyError:
                if self._globalparam is _notexists:
                    raise ValueError(name)
                return self._globalparam

        @property
        def id(self):
            return "-".join(map(str, filter(None, self._idlist)))

        def setmulti(self, valtype, argnames, valset, id, keywords, scopenum,
                     param_index):
            for arg,val in zip(argnames, valset):
                self._checkargnotcontained(arg)
                getattr(self, valtype)[arg] = val
                self.indices[arg] = param_index
                self._arg2scopenum[arg] = scopenum
                if val is _notexists:
                    self._emptyparamspecified = True
            self._idlist.append(id)
            self.keywords.update(keywords)

        def setall(self, funcargs, id, param):
            for x in funcargs:
                self._checkargnotcontained(x)
            self.funcargs.update(funcargs)
            if id is not _notexists:
                self._idlist.append(id)
            if param is not _notexists:
                assert self._globalparam is _notexists
                self._globalparam = param
            for arg in funcargs:
                self._arg2scopenum[arg] = scopenum_function

    class FuncargnamesCompatAttr:
        """ helper class so that Metafunc, Function and FixtureRequest
        don't need to each define the "funcargnames" compatibility attribute.
        """
        @property
        def funcargnames(self):
            """ alias attribute for ``fixturenames`` for pre-2.3 compatibility"""
            return self.fixturenames

    class Metafunc(FuncargnamesCompatAttr):
        """
        Metafunc objects are passed to the ``pytest_generate_tests`` hook.
        They help to inspect a test function and to generate tests according to
        test configuration or values specified in the class or module where a
        test function is defined.

        :ivar fixturenames: set of fixture names required by the test function

        :ivar function: underlying python test function

        :ivar cls: class object where the test function is defined in or ``None``.

        :ivar module: the module object where the test function is defined in.

        :ivar config: access to the :class:`_pytest.config.Config` object for the
            test session.

        :ivar funcargnames:
            .. deprecated:: 2.3
                Use ``fixturenames`` instead.
        """
        def __init__(self, function, fixtureinfo, config, cls=None, module=None):
            self.config = config
            self.module = module
            self.function = function
            self.fixturenames = fixtureinfo.names_closure
            self._arg2fixturedefs = fixtureinfo.name2fixturedefs
            self.cls = cls
            self._calls = []
            self._ids = py.builtin.set()

        def parametrize(self, argnames, argvalues, indirect=False, ids=None,
            scope=None):
            """ Add new invocations to the underlying test function using the list
            of argvalues for the given argnames.  Parametrization is performed
            during the collection phase.  If you need to setup expensive resources
            see about setting indirect=True to do it rather at test setup time.

            :arg argnames: a comma-separated string denoting one or more argument
                           names, or a list/tuple of argument strings.

            :arg argvalues: The list of argvalues determines how often a
                test is invoked with different argument values.  If only one
                argname was specified argvalues is a list of simple values.  If N
                argnames were specified, argvalues must be a list of N-tuples,
                where each tuple-element specifies a value for its respective
                argname.

            :arg indirect: if True each argvalue corresponding to an argname will
                be passed as request.param to its respective argname fixture
                function so that it can perform more expensive setups during the
                setup phase of a test rather than at collection time.

            :arg ids: list of string ids, or a callable.
                If strings, each is corresponding to the argvalues so that they are
                part of the test id.
                If callable, it should take one argument (a single argvalue) and return
                a string or return None. If None, the automatically generated id for that
                argument will be used.
                If no ids are provided they will be generated automatically from
                the argvalues.

            :arg scope: if specified it denotes the scope of the parameters.
                The scope is used for grouping tests by parameter instances.
                It will also override any fixture-function defined scope, allowing
                to set a dynamic scope using test context or configuration.
            """

            # individual parametrized argument sets can be wrapped in a series
            # of markers in which case we unwrap the values and apply the mark
            # at Function init
            newkeywords = {}
            unwrapped_argvalues = []
            for i, argval in enumerate(argvalues):
                while isinstance(argval, MarkDecorator):
                    newmark = MarkDecorator(argval.markname,
                                            argval.args[:-1], argval.kwargs)
                    newmarks = newkeywords.setdefault(i, {})
                    newmarks[newmark.markname] = newmark
                    argval = argval.args[-1]
                unwrapped_argvalues.append(argval)
            argvalues = unwrapped_argvalues

            if not isinstance(argnames, (tuple, list)):
                argnames = [x.strip() for x in argnames.split(",") if x.strip()]
                if len(argnames) == 1:
                    argvalues = [(val,) for val in argvalues]
            if not argvalues:
                argvalues = [(_notexists,) * len(argnames)]

            if scope is None:
                scope = "function"
            scopenum = scopes.index(scope)
            if not indirect:
                #XXX should we also check for the opposite case?
                for arg in argnames:
                    if arg not in self.fixturenames:
                        raise ValueError("%r uses no fixture %r" %(
                                         self.function, arg))
            valtype = indirect and "params" or "funcargs"
            idfn = None
            if callable(ids):
                idfn = ids
                ids = None
            if ids and len(ids) != len(argvalues):
                raise ValueError('%d tests specified with %d ids' %(
                                 len(argvalues), len(ids)))
            if not ids:
                ids = idmaker(argnames, argvalues, idfn)
            newcalls = []
            for callspec in self._calls or [CallSpec2(self)]:
                for param_index, valset in enumerate(argvalues):
                    assert len(valset) == len(argnames)
                    newcallspec = callspec.copy(self)
                    newcallspec.setmulti(valtype, argnames, valset, ids[param_index],
                                         newkeywords.get(param_index, {}), scopenum,
                                         param_index)
                    newcalls.append(newcallspec)
            self._calls = newcalls

        def addcall(self, funcargs=None, id=_notexists, param=_notexists):
            """ (deprecated, use parametrize) Add a new call to the underlying
            test function during the collection phase of a test run.  Note that
            request.addcall() is called during the test collection phase prior and
            independently to actual test execution.  You should only use addcall()
            if you need to specify multiple arguments of a test function.

            :arg funcargs: argument keyword dictionary used when invoking
                the test function.

            :arg id: used for reporting and identification purposes.  If you
                don't supply an `id` an automatic unique id will be generated.

            :arg param: a parameter which will be exposed to a later fixture function
                invocation through the ``request.param`` attribute.
            """
            assert funcargs is None or isinstance(funcargs, dict)
            if funcargs is not None:
                for name in funcargs:
                    if name not in self.fixturenames:
                        pytest.fail("funcarg %r not used in this function." % name)
            else:
                funcargs = {}
            if id is None:
                raise ValueError("id=None not allowed")
            if id is _notexists:
                id = len(self._calls)
            id = str(id)
            if id in self._ids:
                raise ValueError("duplicate id %r" % id)
            self._ids.add(id)

            cs = CallSpec2(self)
            cs.setall(funcargs, id, param)
            self._calls.append(cs)

    def _idval(val, argname, idx, idfn):
        if idfn:
            try:
                s = idfn(val)
                if s:
                    return s
            except Exception:
                pass

        if isinstance(val, (float, int, str, bool, NoneType)):
            return str(val)
        elif isinstance(val, REGEX_TYPE):
            return val.pattern
        elif enum is not None and isinstance(val, enum.Enum):
            return str(val)
        elif isclass(val) and hasattr(val, '__name__'):
            return val.__name__
        return str(argname)+str(idx)

    def _idvalset(idx, valset, argnames, idfn):
        this_id = [_idval(val, argname, idx, idfn)
                   for val, argname in zip(valset, argnames)]
        return "-".join(this_id)

    def idmaker(argnames, argvalues, idfn=None):
        ids = [_idvalset(valindex, valset, argnames, idfn)
               for valindex, valset in enumerate(argvalues)]
        if len(set(ids)) < len(ids):
            # user may have provided a bad idfn which means the ids are not unique
            ids = [str(i) + testid for i, testid in enumerate(ids)]
        return ids

    def showfixtures(config):
        from _pytest.main import wrap_session
        return wrap_session(config, _showfixtures_main)

    def _showfixtures_main(config, session):
        import _pytest.config
        session.perform_collect()
        curdir = py.path.local()
        tw = _pytest.config.create_terminal_writer(config)
        verbose = config.getvalue("verbose")

        fm = session._fixturemanager

        available = []
        for argname, fixturedefs in fm._arg2fixturedefs.items():
            assert fixturedefs is not None
            if not fixturedefs:
                continue
            fixturedef = fixturedefs[-1]
            loc = getlocation(fixturedef.func, curdir)
            available.append((len(fixturedef.baseid),
                              fixturedef.func.__module__,
                              curdir.bestrelpath(loc),
                              fixturedef.argname, fixturedef))

        available.sort()
        currentmodule = None
        for baseid, module, bestrel, argname, fixturedef in available:
            if currentmodule != module:
                if not module.startswith("_pytest."):
                    tw.line()
                    tw.sep("-", "fixtures defined from %s" %(module,))
                    currentmodule = module
            if verbose <= 0 and argname[0] == "_":
                continue
            if verbose > 0:
                funcargspec = "%s -- %s" %(argname, bestrel,)
            else:
                funcargspec = argname
            tw.line(funcargspec, green=True)
            loc = getlocation(fixturedef.func, curdir)
            doc = fixturedef.func.__doc__ or ""
            if doc:
                for line in doc.strip().split("\n"):
                    tw.line("    " + line.strip())
            else:
                tw.line("    %s: no docstring available" %(loc,),
                    red=True)

    def getlocation(function, curdir):
        import inspect
        fn = py.path.local(inspect.getfile(function))
        lineno = py.builtin._getcode(function).co_firstlineno
        if fn.relto(curdir):
            fn = fn.relto(curdir)
        return "%s:%d" %(fn, lineno+1)

    # builtin pytest.raises helper

    def raises(expected_exception, *args, **kwargs):
        """ assert that a code block/function call raises @expected_exception
        and raise a failure exception otherwise.

        This helper produces a ``py.code.ExceptionInfo()`` object.

        If using Python 2.5 or above, you may use this function as a
        context manager::

            >>> with raises(ZeroDivisionError):
            ...    1/0

        Or you can specify a callable by passing a to-be-called lambda::

            >>> raises(ZeroDivisionError, lambda: 1/0)
            <ExceptionInfo ...>

        or you can specify an arbitrary callable with arguments::

            >>> def f(x): return 1/x
            ...
            >>> raises(ZeroDivisionError, f, 0)
            <ExceptionInfo ...>
            >>> raises(ZeroDivisionError, f, x=0)
            <ExceptionInfo ...>

        A third possibility is to use a string to be executed::

            >>> raises(ZeroDivisionError, "f(0)")
            <ExceptionInfo ...>

        Performance note:
        -----------------

        Similar to caught exception objects in Python, explicitly clearing
        local references to returned ``py.code.ExceptionInfo`` objects can
        help the Python interpreter speed up its garbage collection.

        Clearing those references breaks a reference cycle
        (``ExceptionInfo`` --> caught exception --> frame stack raising
        the exception --> current frame stack --> local variables -->
        ``ExceptionInfo``) which makes Python keep all objects referenced
        from that cycle (including all local variables in the current
        frame) alive until the next cyclic garbage collection run. See the
        official Python ``try`` statement documentation for more detailed
        information.

        """
        __tracebackhide__ = True
        if expected_exception is AssertionError:
            # we want to catch a AssertionError
            # replace our subclass with the builtin one
            # see https://github.com/pytest-dev/pytest/issues/176
            from _pytest.assertion.util import BuiltinAssertionError \
                as expected_exception
        msg = ("exceptions must be old-style classes or"
               " derived from BaseException, not %s")
        if isinstance(expected_exception, tuple):
            for exc in expected_exception:
                if not isclass(exc):
                    raise TypeError(msg % type(exc))
        elif not isclass(expected_exception):
            raise TypeError(msg % type(expected_exception))

        if not args:
            return RaisesContext(expected_exception)
        elif isinstance(args[0], str):
            code, = args
            assert isinstance(code, str)
            frame = sys._getframe(1)
            loc = frame.f_locals.copy()
            loc.update(kwargs)
            #print "raises frame scope: %r" % frame.f_locals
            try:
                code = py.code.Source(code).compile()
                py.builtin.exec_(code, frame.f_globals, loc)
                # XXX didn'T mean f_globals == f_locals something special?
                #     this is destroyed here ...
            except expected_exception:
                return py.code.ExceptionInfo()
        else:
            func = args[0]
            try:
                func(*args[1:], **kwargs)
            except expected_exception:
                return py.code.ExceptionInfo()
        pytest.fail("DID NOT RAISE")

    class RaisesContext(object):
        def __init__(self, expected_exception):
            self.expected_exception = expected_exception
            self.excinfo = None

        def __enter__(self):
            self.excinfo = object.__new__(py.code.ExceptionInfo)
            return self.excinfo

        def __exit__(self, *tp):
            __tracebackhide__ = True
            if tp[0] is None:
                pytest.fail("DID NOT RAISE")
            if sys.version_info < (2, 7):
                # py26: on __exit__() exc_value often does not contain the
                # exception value.
                # http://bugs.python.org/issue7853
                if not isinstance(tp[1], BaseException):
                    exc_type, value, traceback = tp
                    tp = exc_type, exc_type(value), traceback
            self.excinfo.__init__(tp)
            return issubclass(self.excinfo.type, self.expected_exception)

    #
    #  the basic pytest Function item
    #

    class Function(FunctionMixin, pytest.Item, FuncargnamesCompatAttr):
        """ a Function Item is responsible for setting up and executing a
        Python test function.
        """
        _genid = None
        def __init__(self, name, parent, args=None, config=None,
                     callspec=None, callobj=NOTSET, keywords=None, session=None,
                     fixtureinfo=None):
            super(Function, self).__init__(name, parent, config=config,
                                           session=session)
            self._args = args
            if callobj is not NOTSET:
                self.obj = callobj

            self.keywords.update(self.obj.__dict__)
            if callspec:
                self.callspec = callspec
                self.keywords.update(callspec.keywords)
            if keywords:
                self.keywords.update(keywords)

            if fixtureinfo is None:
                fixtureinfo = self.session._fixturemanager.getfixtureinfo(
                    self.parent, self.obj, self.cls,
                    funcargs=not self._isyieldedfunction())
            self._fixtureinfo = fixtureinfo
            self.fixturenames = fixtureinfo.names_closure
            self._initrequest()

        def _initrequest(self):
            self.funcargs = {}
            if self._isyieldedfunction():
                assert not hasattr(self, "callspec"), (
                    "yielded functions (deprecated) cannot have funcargs")
            else:
                if hasattr(self, "callspec"):
                    callspec = self.callspec
                    assert not callspec.funcargs
                    self._genid = callspec.id
                    if hasattr(callspec, "param"):
                        self.param = callspec.param
            self._request = FixtureRequest(self)

        @property
        def function(self):
            "underlying python 'function' object"
            return getattr(self.obj, 'im_func', self.obj)

        def _getobj(self):
            name = self.name
            i = name.find("[") # parametrization
            if i != -1:
                name = name[:i]
            return getattr(self.parent.obj, name)

        @property
        def _pyfuncitem(self):
            "(compatonly) for code expecting pytest-2.2 style request objects"
            return self

        def _isyieldedfunction(self):
            return getattr(self, "_args", None) is not None

        def runtest(self):
            """ execute the underlying test function. """
            self.ihook.pytest_pyfunc_call(pyfuncitem=self)

        def setup(self):
            # check if parametrization happend with an empty list
            try:
                self.callspec._emptyparamspecified
            except AttributeError:
                pass
            else:
                fs, lineno = self._getfslineno()
                pytest.skip("got empty parameter set, function %s at %s:%d" %(
                    self.function.__name__, fs, lineno))
            super(Function, self).setup()
            fillfixtures(self)

    scope2props = dict(session=())
    scope2props["module"] = ("fspath", "module")
    scope2props["class"] = scope2props["module"] + ("cls",)
    scope2props["instance"] = scope2props["class"] + ("instance", )
    scope2props["function"] = scope2props["instance"] + ("function", "keywords")

    def scopeproperty(name=None, doc=None):
        def decoratescope(func):
            scopename = name or func.__name__
            def provide(self):
                if func.__name__ in scope2props[self.scope]:
                    return func(self)
                raise AttributeError("%s not available in %s-scoped context" % (
                    scopename, self.scope))
            return property(provide, None, None, func.__doc__)
        return decoratescope

    class FixtureRequest(FuncargnamesCompatAttr):
        """ A request for a fixture from a test or fixture function.

        A request object gives access to the requesting test context
        and has an optional ``param`` attribute in case
        the fixture is parametrized indirectly.
        """

        def __init__(self, pyfuncitem):
            self._pyfuncitem = pyfuncitem
            #: fixture for which this request is being performed
            self.fixturename = None
            #: Scope string, one of "function", "cls", "module", "session"
            self.scope = "function"
            self._funcargs  = {}
            self._fixturedefs = {}
            fixtureinfo = pyfuncitem._fixtureinfo
            self._arg2fixturedefs = fixtureinfo.name2fixturedefs.copy()
            self._arg2index = {}
            self.fixturenames = fixtureinfo.names_closure
            self._fixturemanager = pyfuncitem.session._fixturemanager

        @property
        def node(self):
            """ underlying collection node (depends on current request scope)"""
            return self._getscopeitem(self.scope)

        def _getnextfixturedef(self, argname):
            fixturedefs = self._arg2fixturedefs.get(argname, None)
            if fixturedefs is None:
                # we arrive here because of a  a dynamic call to
                # getfuncargvalue(argname) usage which was naturally
                # not known at parsing/collection time
                fixturedefs = self._fixturemanager.getfixturedefs(
                                argname, self._pyfuncitem.parent.nodeid)
                self._arg2fixturedefs[argname] = fixturedefs
            # fixturedefs list is immutable so we maintain a decreasing index
            index = self._arg2index.get(argname, 0) - 1
            if fixturedefs is None or (-index > len(fixturedefs)):
                raise FixtureLookupError(argname, self)
            self._arg2index[argname] = index
            return fixturedefs[index]

        @property
        def config(self):
            """ the pytest config object associated with this request. """
            return self._pyfuncitem.config

        @scopeproperty()
        def function(self):
            """ test function object if the request has a per-function scope. """
            return self._pyfuncitem.obj

        @scopeproperty("class")
        def cls(self):
            """ class (can be None) where the test function was collected. """
            clscol = self._pyfuncitem.getparent(pytest.Class)
            if clscol:
                return clscol.obj

        @property
        def instance(self):
            """ instance (can be None) on which test function was collected. """
            # unittest support hack, see _pytest.unittest.TestCaseFunction
            try:
                return self._pyfuncitem._testcase
            except AttributeError:
                function = getattr(self, "function", None)
                if function is not None:
                    return py.builtin._getimself(function)

        @scopeproperty()
        def module(self):
            """ python module object where the test function was collected. """
            return self._pyfuncitem.getparent(pytest.Module).obj

        @scopeproperty()
        def fspath(self):
            """ the file system path of the test module which collected this test. """
            return self._pyfuncitem.fspath

        @property
        def keywords(self):
            """ keywords/markers dictionary for the underlying node. """
            return self.node.keywords

        @property
        def session(self):
            """ pytest session object. """
            return self._pyfuncitem.session

        def addfinalizer(self, finalizer):
            """ add finalizer/teardown function to be called after the
            last test within the requesting test context finished
            execution. """
            # XXX usually this method is shadowed by fixturedef specific ones
            self._addfinalizer(finalizer, scope=self.scope)

        def _addfinalizer(self, finalizer, scope):
            colitem = self._getscopeitem(scope)
            self._pyfuncitem.session._setupstate.addfinalizer(
                finalizer=finalizer, colitem=colitem)

        def applymarker(self, marker):
            """ Apply a marker to a single test function invocation.
            This method is useful if you don't want to have a keyword/marker
            on all function invocations.

            :arg marker: a :py:class:`_pytest.mark.MarkDecorator` object
                created by a call to ``pytest.mark.NAME(...)``.
            """
            try:
                self.node.keywords[marker.markname] = marker
            except AttributeError:
                raise ValueError(marker)

        def raiseerror(self, msg):
            """ raise a FixtureLookupError with the given message. """
            raise self._fixturemanager.FixtureLookupError(None, self, msg)

        def _fillfixtures(self):
            item = self._pyfuncitem
            fixturenames = getattr(item, "fixturenames", self.fixturenames)
            for argname in fixturenames:
                if argname not in item.funcargs:
                    item.funcargs[argname] = self.getfuncargvalue(argname)

        def cached_setup(self, setup, teardown=None, scope="module", extrakey=None):
            """ (deprecated) Return a testing resource managed by ``setup`` &
            ``teardown`` calls.  ``scope`` and ``extrakey`` determine when the
            ``teardown`` function will be called so that subsequent calls to
            ``setup`` would recreate the resource.  With pytest-2.3 you often
            do not need ``cached_setup()`` as you can directly declare a scope
            on a fixture function and register a finalizer through
            ``request.addfinalizer()``.

            :arg teardown: function receiving a previously setup resource.
            :arg setup: a no-argument function creating a resource.
            :arg scope: a string value out of ``function``, ``class``, ``module``
                or ``session`` indicating the caching lifecycle of the resource.
            :arg extrakey: added to internal caching key of (funcargname, scope).
            """
            if not hasattr(self.config, '_setupcache'):
                self.config._setupcache = {} # XXX weakref?
            cachekey = (self.fixturename, self._getscopeitem(scope), extrakey)
            cache = self.config._setupcache
            try:
                val = cache[cachekey]
            except KeyError:
                self._check_scope(self.fixturename, self.scope, scope)
                val = setup()
                cache[cachekey] = val
                if teardown is not None:
                    def finalizer():
                        del cache[cachekey]
                        teardown(val)
                    self._addfinalizer(finalizer, scope=scope)
            return val

        def getfuncargvalue(self, argname):
            """ Dynamically retrieve a named fixture function argument.

            As of pytest-2.3, it is easier and usually better to access other
            fixture values by stating it as an input argument in the fixture
            function.  If you only can decide about using another fixture at test
            setup time, you may use this function to retrieve it inside a fixture
            function body.
            """
            return self._get_active_fixturedef(argname).cached_result[0]

        def _get_active_fixturedef(self, argname):
            try:
                return self._fixturedefs[argname]
            except KeyError:
                try:
                    fixturedef = self._getnextfixturedef(argname)
                except FixtureLookupError:
                    if argname == "request":
                        class PseudoFixtureDef:
                            cached_result = (self, [0], None)
                            scope = "function"
                        return PseudoFixtureDef
                    raise
            # remove indent to prevent the python3 exception
            # from leaking into the call
            result = self._getfuncargvalue(fixturedef)
            self._funcargs[argname] = result
            self._fixturedefs[argname] = fixturedef
            return fixturedef

        def _get_fixturestack(self):
            current = self
            l = []
            while 1:
                fixturedef = getattr(current, "_fixturedef", None)
                if fixturedef is None:
                    l.reverse()
                    return l
                l.append(fixturedef)
                current = current._parent_request

        def _getfuncargvalue(self, fixturedef):
            # prepare a subrequest object before calling fixture function
            # (latter managed by fixturedef)
            argname = fixturedef.argname
            funcitem = self._pyfuncitem
            scope = fixturedef.scope
            try:
                param = funcitem.callspec.getparam(argname)
            except (AttributeError, ValueError):
                param = NOTSET
                param_index = 0
            else:
                # indices might not be set if old-style metafunc.addcall() was used
                param_index = funcitem.callspec.indices.get(argname, 0)
                # if a parametrize invocation set a scope it will override
                # the static scope defined with the fixture function
                paramscopenum = funcitem.callspec._arg2scopenum.get(argname)
                if paramscopenum is not None:
                    scope = scopes[paramscopenum]

            subrequest = SubRequest(self, scope, param, param_index, fixturedef)

            # check if a higher-level scoped fixture accesses a lower level one
            subrequest._check_scope(argname, self.scope, scope)

            # clear sys.exc_info before invoking the fixture (python bug?)
            # if its not explicitly cleared it will leak into the call
            exc_clear()
            try:
                # call the fixture function
                val = fixturedef.execute(request=subrequest)
            finally:
                # if fixture function failed it might have registered finalizers
                self.session._setupstate.addfinalizer(fixturedef.finish,
                                                      subrequest.node)
            return val

        def _check_scope(self, argname, invoking_scope, requested_scope):
            if argname == "request":
                return
            if scopemismatch(invoking_scope, requested_scope):
                # try to report something helpful
                lines = self._factorytraceback()
                pytest.fail("ScopeMismatch: You tried to access the %r scoped "
                    "fixture %r with a %r scoped request object, "
                    "involved factories\n%s" %(
                    (requested_scope, argname, invoking_scope, "\n".join(lines))),
                    pytrace=False)

        def _factorytraceback(self):
            lines = []
            for fixturedef in self._get_fixturestack():
                factory = fixturedef.func
                fs, lineno = getfslineno(factory)
                p = self._pyfuncitem.session.fspath.bestrelpath(fs)
                args = inspect.formatargspec(*inspect.getargspec(factory))
                lines.append("%s:%d:  def %s%s" %(
                    p, lineno, factory.__name__, args))
            return lines

        def _getscopeitem(self, scope):
            if scope == "function":
                # this might also be a non-function Item despite its attribute name
                return self._pyfuncitem
            node = get_scope_node(self._pyfuncitem, scope)
            if node is None and scope == "class":
                # fallback to function item itself
                node = self._pyfuncitem
            assert node
            return node

        def __repr__(self):
            return "<FixtureRequest for %r>" %(self.node)

    class SubRequest(FixtureRequest):
        """ a sub request for handling getting a fixture from a
        test function/fixture. """
        def __init__(self, request, scope, param, param_index, fixturedef):
            self._parent_request = request
            self.fixturename = fixturedef.argname
            if param is not NOTSET:
                self.param = param
            self.param_index = param_index
            self.scope = scope
            self._fixturedef = fixturedef
            self.addfinalizer = fixturedef.addfinalizer
            self._pyfuncitem = request._pyfuncitem
            self._funcargs  = request._funcargs
            self._fixturedefs = request._fixturedefs
            self._arg2fixturedefs = request._arg2fixturedefs
            self._arg2index = request._arg2index
            self.fixturenames = request.fixturenames
            self._fixturemanager = request._fixturemanager

        def __repr__(self):
            return "<SubRequest %r for %r>" % (self.fixturename, self._pyfuncitem)

    class ScopeMismatchError(Exception):
        """ A fixture function tries to use a different fixture function which
        which has a lower scope (e.g. a Session one calls a function one)
        """

    scopes = "session module class function".split()
    scopenum_function = scopes.index("function")
    def scopemismatch(currentscope, newscope):
        return scopes.index(newscope) > scopes.index(currentscope)

    class FixtureLookupError(LookupError):
        """ could not return a requested Fixture (missing or invalid). """
        def __init__(self, argname, request, msg=None):
            self.argname = argname
            self.request = request
            self.fixturestack = request._get_fixturestack()
            self.msg = msg

        def formatrepr(self):
            tblines = []
            addline = tblines.append
            stack = [self.request._pyfuncitem.obj]
            stack.extend(map(lambda x: x.func, self.fixturestack))
            msg = self.msg
            if msg is not None:
                stack = stack[:-1] # the last fixture raise an error, let's present
                                   # it at the requesting side
            for function in stack:
                fspath, lineno = getfslineno(function)
                try:
                    lines, _ = inspect.getsourcelines(get_real_func(function))
                except IOError:
                    error_msg = "file %s, line %s: source code not available"
                    addline(error_msg % (fspath, lineno+1))
                else:
                    addline("file %s, line %s" % (fspath, lineno+1))
                    for i, line in enumerate(lines):
                        line = line.rstrip()
                        addline("  " + line)
                        if line.lstrip().startswith('def'):
                            break

            if msg is None:
                fm = self.request._fixturemanager
                available = []
                for name, fixturedef in fm._arg2fixturedefs.items():
                    parentid = self.request._pyfuncitem.parent.nodeid
                    faclist = list(fm._matchfactories(fixturedef, parentid))
                    if faclist:
                        available.append(name)
                msg = "fixture %r not found" % (self.argname,)
                msg += "\n available fixtures: %s" %(", ".join(available),)
                msg += "\n use 'py.test --fixtures [testpath]' for help on them."

            return FixtureLookupErrorRepr(fspath, lineno, tblines, msg, self.argname)

    class FixtureLookupErrorRepr(TerminalRepr):
        def __init__(self, filename, firstlineno, tblines, errorstring, argname):
            self.tblines = tblines
            self.errorstring = errorstring
            self.filename = filename
            self.firstlineno = firstlineno
            self.argname = argname

        def toterminal(self, tw):
            #tw.line("FixtureLookupError: %s" %(self.argname), red=True)
            for tbline in self.tblines:
                tw.line(tbline.rstrip())
            for line in self.errorstring.split("\n"):
                tw.line("        " + line.strip(), red=True)
            tw.line()
            tw.line("%s:%d" % (self.filename, self.firstlineno+1))

    class FixtureManager:
        """
        pytest fixtures definitions and information is stored and managed
        from this class.

        During collection fm.parsefactories() is called multiple times to parse
        fixture function definitions into FixtureDef objects and internal
        data structures.

        During collection of test functions, metafunc-mechanics instantiate
        a FuncFixtureInfo object which is cached per node/func-name.
        This FuncFixtureInfo object is later retrieved by Function nodes
        which themselves offer a fixturenames attribute.

        The FuncFixtureInfo object holds information about fixtures and FixtureDefs
        relevant for a particular function.  An initial list of fixtures is
        assembled like this:

        - ini-defined usefixtures
        - autouse-marked fixtures along the collection chain up from the function
        - usefixtures markers at module/class/function level
        - test function funcargs

        Subsequently the funcfixtureinfo.fixturenames attribute is computed
        as the closure of the fixtures needed to setup the initial fixtures,
        i. e. fixtures needed by fixture functions themselves are appended
        to the fixturenames list.

        Upon the test-setup phases all fixturenames are instantiated, retrieved
        by a lookup of their FuncFixtureInfo.
        """

        _argprefix = "pytest_funcarg__"
        FixtureLookupError = FixtureLookupError
        FixtureLookupErrorRepr = FixtureLookupErrorRepr

        def __init__(self, session):
            self.session = session
            self.config = session.config
            self._arg2fixturedefs = {}
            self._holderobjseen = set()
            self._arg2finish = {}
            self._nodeid_and_autousenames = [("", self.config.getini("usefixtures"))]
            session.config.pluginmanager.register(self, "funcmanage")

        def getfixtureinfo(self, node, func, cls, funcargs=True):
            if funcargs and not hasattr(node, "nofuncargs"):
                if cls is not None:
                    startindex = 1
                else:
                    startindex = None
                argnames = getfuncargnames(func, startindex)
            else:
                argnames = ()
            usefixtures = getattr(func, "usefixtures", None)
            initialnames = argnames
            if usefixtures is not None:
                initialnames = usefixtures.args + initialnames
            fm = node.session._fixturemanager
            names_closure, arg2fixturedefs = fm.getfixtureclosure(initialnames,
                                                                  node)
            return FuncFixtureInfo(argnames, names_closure, arg2fixturedefs)

        def pytest_plugin_registered(self, plugin):
            nodeid = None
            try:
                p = py.path.local(plugin.__file__)
            except AttributeError:
                pass
            else:
                # construct the base nodeid which is later used to check
                # what fixtures are visible for particular tests (as denoted
                # by their test id)
                if p.basename.startswith("conftest.py"):
                    nodeid = p.dirpath().relto(self.config.rootdir)
                    if p.sep != "/":
                        nodeid = nodeid.replace(p.sep, "/")
            self.parsefactories(plugin, nodeid)

        def _getautousenames(self, nodeid):
            """ return a tuple of fixture names to be used. """
            autousenames = []
            for baseid, basenames in self._nodeid_and_autousenames:
                if nodeid.startswith(baseid):
                    if baseid:
                        i = len(baseid)
                        nextchar = nodeid[i:i+1]
                        if nextchar and nextchar not in ":/":
                            continue
                    autousenames.extend(basenames)
            # make sure autousenames are sorted by scope, scopenum 0 is session
            autousenames.sort(
                key=lambda x: self._arg2fixturedefs[x][-1].scopenum)
            return autousenames

        def getfixtureclosure(self, fixturenames, parentnode):
            # collect the closure of all fixtures , starting with the given
            # fixturenames as the initial set.  As we have to visit all
            # factory definitions anyway, we also return a arg2fixturedefs
            # mapping so that the caller can reuse it and does not have
            # to re-discover fixturedefs again for each fixturename
            # (discovering matching fixtures for a given name/node is expensive)

            parentid = parentnode.nodeid
            fixturenames_closure = self._getautousenames(parentid)
            def merge(otherlist):
                for arg in otherlist:
                    if arg not in fixturenames_closure:
                        fixturenames_closure.append(arg)
            merge(fixturenames)
            arg2fixturedefs = {}
            lastlen = -1
            while lastlen != len(fixturenames_closure):
                lastlen = len(fixturenames_closure)
                for argname in fixturenames_closure:
                    if argname in arg2fixturedefs:
                        continue
                    fixturedefs = self.getfixturedefs(argname, parentid)
                    if fixturedefs:
                        arg2fixturedefs[argname] = fixturedefs
                        merge(fixturedefs[-1].argnames)
            return fixturenames_closure, arg2fixturedefs

        def pytest_generate_tests(self, metafunc):
            for argname in metafunc.fixturenames:
                faclist = metafunc._arg2fixturedefs.get(argname)
                if faclist:
                    fixturedef = faclist[-1]
                    if fixturedef.params is not None:
                        func_params = getattr(getattr(metafunc.function, 'parametrize', None), 'args', [[None]])
                        # skip directly parametrized arguments
                        if argname not in func_params:
                            metafunc.parametrize(argname, fixturedef.params,
                                                 indirect=True, scope=fixturedef.scope,
                                                 ids=fixturedef.ids)
                else:
                    continue # will raise FixtureLookupError at setup time

        def pytest_collection_modifyitems(self, items):
            # separate parametrized setups
            items[:] = reorder_items(items)

        def parsefactories(self, node_or_obj, nodeid=NOTSET, unittest=False):
            if nodeid is not NOTSET:
                holderobj = node_or_obj
            else:
                holderobj = node_or_obj.obj
                nodeid = node_or_obj.nodeid
            if holderobj in self._holderobjseen:
                return
            self._holderobjseen.add(holderobj)
            autousenames = []
            for name in dir(holderobj):
                obj = getattr(holderobj, name, None)
                if not callable(obj):
                    continue
                # fixture functions have a pytest_funcarg__ prefix (pre-2.3 style)
                # or are "@pytest.fixture" marked
                marker = getfixturemarker(obj)
                if marker is None:
                    if not name.startswith(self._argprefix):
                        continue
                    marker = defaultfuncargprefixmarker
                    name = name[len(self._argprefix):]
                elif not isinstance(marker, FixtureFunctionMarker):
                    # magic globals  with __getattr__ might have got us a wrong
                    # fixture attribute
                    continue
                else:
                    assert not name.startswith(self._argprefix)
                fixturedef = FixtureDef(self, nodeid, name, obj,
                                        marker.scope, marker.params,
                                        yieldctx=marker.yieldctx,
                                        unittest=unittest, ids=marker.ids)
                faclist = self._arg2fixturedefs.setdefault(name, [])
                if fixturedef.has_location:
                    faclist.append(fixturedef)
                else:
                    # fixturedefs with no location are at the front
                    # so this inserts the current fixturedef after the
                    # existing fixturedefs from external plugins but
                    # before the fixturedefs provided in conftests.
                    i = len([f for f in faclist if not f.has_location])
                    faclist.insert(i, fixturedef)
                if marker.autouse:
                    autousenames.append(name)
            if autousenames:
                self._nodeid_and_autousenames.append((nodeid or '', autousenames))

        def getfixturedefs(self, argname, nodeid):
            try:
                fixturedefs = self._arg2fixturedefs[argname]
            except KeyError:
                return None
            else:
                return tuple(self._matchfactories(fixturedefs, nodeid))

        def _matchfactories(self, fixturedefs, nodeid):
            for fixturedef in fixturedefs:
                if nodeid.startswith(fixturedef.baseid):
                    yield fixturedef

    def fail_fixturefunc(fixturefunc, msg):
        fs, lineno = getfslineno(fixturefunc)
        location = "%s:%s" % (fs, lineno+1)
        source = py.code.Source(fixturefunc)
        pytest.fail(msg + ":\n\n" + str(source.indent()) + "\n" + location,
                    pytrace=False)

    def call_fixture_func(fixturefunc, request, kwargs, yieldctx):
        if yieldctx:
            if not is_generator(fixturefunc):
                fail_fixturefunc(fixturefunc,
                    msg="yield_fixture requires yield statement in function")
            iter = fixturefunc(**kwargs)
            next = getattr(iter, "__next__", None)
            if next is None:
                next = getattr(iter, "next")
            res = next()
            def teardown():
                try:
                    next()
                except StopIteration:
                    pass
                else:
                    fail_fixturefunc(fixturefunc,
                        "yield_fixture function has more than one 'yield'")
            request.addfinalizer(teardown)
        else:
            if is_generator(fixturefunc):
                fail_fixturefunc(fixturefunc,
                    msg="pytest.fixture functions cannot use ``yield``. "
                        "Instead write and return an inner function/generator "
                        "and let the consumer call and iterate over it.")
            res = fixturefunc(**kwargs)
        return res

    class FixtureDef:
        """ A container for a factory definition. """
        def __init__(self, fixturemanager, baseid, argname, func, scope, params,
                     yieldctx, unittest=False, ids=None):
            self._fixturemanager = fixturemanager
            self.baseid = baseid or ''
            self.has_location = baseid is not None
            self.func = func
            self.argname = argname
            self.scope = scope
            self.scopenum = scopes.index(scope or "function")
            self.params = params
            startindex = unittest and 1 or None
            self.argnames = getfuncargnames(func, startindex=startindex)
            self.yieldctx = yieldctx
            self.unittest = unittest
            self.ids = ids
            self._finalizer = []

        def addfinalizer(self, finalizer):
            self._finalizer.append(finalizer)

        def finish(self):
            try:
                while self._finalizer:
                    func = self._finalizer.pop()
                    func()
            finally:
                # even if finalization fails, we invalidate
                # the cached fixture value
                if hasattr(self, "cached_result"):
                    del self.cached_result

        def execute(self, request):
            # get required arguments and register our own finish()
            # with their finalization
            kwargs = {}
            for argname in self.argnames:
                fixturedef = request._get_active_fixturedef(argname)
                result, arg_cache_key, exc = fixturedef.cached_result
                request._check_scope(argname, request.scope, fixturedef.scope)
                kwargs[argname] = result
                if argname != "request":
                    fixturedef.addfinalizer(self.finish)

            my_cache_key = request.param_index
            cached_result = getattr(self, "cached_result", None)
            if cached_result is not None:
                result, cache_key, err = cached_result
                if my_cache_key == cache_key:
                    if err is not None:
                        py.builtin._reraise(*err)
                    else:
                        return result
                # we have a previous but differently parametrized fixture instance
                # so we need to tear it down before creating a new one
                self.finish()
                assert not hasattr(self, "cached_result")

            fixturefunc = self.func

            if self.unittest:
                if request.instance is not None:
                    # bind the unbound method to the TestCase instance
                    fixturefunc = self.func.__get__(request.instance)
            else:
                # the fixture function needs to be bound to the actual
                # request.instance so that code working with "self" behaves
                # as expected.
                if request.instance is not None:
                    fixturefunc = getimfunc(self.func)
                    if fixturefunc != self.func:
                        fixturefunc = fixturefunc.__get__(request.instance)

            try:
                result = call_fixture_func(fixturefunc, request, kwargs,
                                           self.yieldctx)
            except Exception:
                self.cached_result = (None, my_cache_key, sys.exc_info())
                raise
            self.cached_result = (result, my_cache_key, None)
            return result

        def __repr__(self):
            return ("<FixtureDef name=%r scope=%r baseid=%r >" %
                    (self.argname, self.scope, self.baseid))

    def num_mock_patch_args(function):
        """ return number of arguments used up by mock arguments (if any) """
        patchings = getattr(function, "patchings", None)
        if not patchings:
            return 0
        mock = sys.modules.get("mock", sys.modules.get("unittest.mock", None))
        if mock is not None:
            return len([p for p in patchings
                            if not p.attribute_name and p.new is mock.DEFAULT])
        return len(patchings)

    def getfuncargnames(function, startindex=None):
        # XXX merge with main.py's varnames
        #assert not inspect.isclass(function)
        realfunction = function
        while hasattr(realfunction, "__wrapped__"):
            realfunction = realfunction.__wrapped__
        if startindex is None:
            startindex = inspect.ismethod(function) and 1 or 0
        if realfunction != function:
            startindex += num_mock_patch_args(function)
            function = realfunction
        if isinstance(function, functools.partial):
            argnames = inspect.getargs(py.code.getrawcode(function.func))[0]
            partial = function
            argnames = argnames[len(partial.args):]
            if partial.keywords:
                for kw in partial.keywords:
                    argnames.remove(kw)
        else:
            argnames = inspect.getargs(py.code.getrawcode(function))[0]
        defaults = getattr(function, 'func_defaults',
                           getattr(function, '__defaults__', None)) or ()
        numdefaults = len(defaults)
        if numdefaults:
            return tuple(argnames[startindex:-numdefaults])
        return tuple(argnames[startindex:])

    # algorithm for sorting on a per-parametrized resource setup basis
    # it is called for scopenum==0 (session) first and performs sorting
    # down to the lower scopes such as to minimize number of "high scope"
    # setups and teardowns

    def reorder_items(items):
        argkeys_cache = {}
        for scopenum in range(0, scopenum_function):
            argkeys_cache[scopenum] = d = {}
            for item in items:
                keys = set(get_parametrized_fixture_keys(item, scopenum))
                if keys:
                    d[item] = keys
        return reorder_items_atscope(items, set(), argkeys_cache, 0)

    def reorder_items_atscope(items, ignore, argkeys_cache, scopenum):
        if scopenum >= scopenum_function or len(items) < 3:
            return items
        items_done = []
        while 1:
            items_before, items_same, items_other, newignore = \
                    slice_items(items, ignore, argkeys_cache[scopenum])
            items_before = reorder_items_atscope(
                                items_before, ignore, argkeys_cache,scopenum+1)
            if items_same is None:
                # nothing to reorder in this scope
                assert items_other is None
                return items_done + items_before
            items_done.extend(items_before)
            items = items_same + items_other
            ignore = newignore

    def slice_items(items, ignore, scoped_argkeys_cache):
        # we pick the first item which uses a fixture instance in the
        # requested scope and which we haven't seen yet.  We slice the input
        # items list into a list of items_nomatch, items_same and
        # items_other
        if scoped_argkeys_cache:  # do we need to do work at all?
            it = iter(items)
            # first find a slicing key
            for i, item in enumerate(it):
                argkeys = scoped_argkeys_cache.get(item)
                if argkeys is not None:
                    argkeys = argkeys.difference(ignore)
                    if argkeys:  # found a slicing key
                        slicing_argkey = argkeys.pop()
                        items_before = items[:i]
                        items_same = [item]
                        items_other = []
                        # now slice the remainder of the list
                        for item in it:
                            argkeys = scoped_argkeys_cache.get(item)
                            if argkeys and slicing_argkey in argkeys and \
                                slicing_argkey not in ignore:
                                items_same.append(item)
                            else:
                                items_other.append(item)
                        newignore = ignore.copy()
                        newignore.add(slicing_argkey)
                        return (items_before, items_same, items_other, newignore)
        return items, None, None, None

    def get_parametrized_fixture_keys(item, scopenum):
        """ return list of keys for all parametrized arguments which match
        the specified scope. """
        assert scopenum < scopenum_function  # function
        try:
            cs = item.callspec
        except AttributeError:
            pass
        else:
            # cs.indictes.items() is random order of argnames but
            # then again different functions (items) can change order of
            # arguments so it doesn't matter much probably
            for argname, param_index in cs.indices.items():
                if cs._arg2scopenum[argname] != scopenum:
                    continue
                if scopenum == 0:    # session
                    key = (argname, param_index)
                elif scopenum == 1:  # module
                    key = (argname, param_index, item.fspath)
                elif scopenum == 2:  # class
                    key = (argname, param_index, item.fspath, item.cls)
                yield key

    def xunitsetup(obj, name):
        meth = getattr(obj, name, None)
        if getfixturemarker(meth) is None:
            return meth

    def getfixturemarker(obj):
        """ return fixturemarker or None if it doesn't exist or raised
        exceptions."""
        try:
            return getattr(obj, "_pytestfixturefunction", None)
        except KeyboardInterrupt:
            raise
        except Exception:
            # some objects raise errors like request (from flask import request)
            # we don't expect them to be fixture functions
            return None

    scopename2class = {
        'class': Class,
        'module': Module,
        'function': pytest.Item,
    }
    def get_scope_node(node, scope):
        cls = scopename2class.get(scope)
        if cls is None:
            if scope == "session":
                return node.session
            raise ValueError("unknown scope")
        return node.getparent(cls)