Use funcsigs and inspect.signature to do function argument analysis

AUTHORS

@@ -30,6 +30,7 @@ Brianna Laugher
 Bruno Oliveira
 Cal Leeming
 Carl Friedrich Bolz
+Ceridwen
 Charles Cloud
 Charnjit SiNGH (CCSJ)
 Chris Lamb

_pytest/compat.py

@@ -2,11 +2,12 @@
 python version compatibility code
 """
 from __future__ import absolute_import, division, print_function
-import sys
+
+import codecs
+import functools
 import inspect
 import re
-import functools
-import codecs
+import sys
 
 import py
 
@@ -25,19 +26,23 @@
 _PY2 = not _PY3
 
 
+if _PY3:
+    from inspect import signature, Parameter as Parameter
+else:
+    from funcsigs import signature, Parameter as Parameter
+
+
 NoneType = type(None)
 NOTSET = object()
 
 PY35 = sys.version_info[:2] >= (3, 5)
 PY36 = sys.version_info[:2] >= (3, 6)
 MODULE_NOT_FOUND_ERROR = 'ModuleNotFoundError' if PY36 else 'ImportError'
 
-if hasattr(inspect, 'signature'):
-    def _format_args(func):
-        return str(inspect.signature(func))
-else:
-    def _format_args(func):
-        return inspect.formatargspec(*inspect.getargspec(func))
+
+def _format_args(func):
+    return str(signature(func))
+
 
 isfunction = inspect.isfunction
 isclass = inspect.isclass
@@ -63,7 +68,6 @@ def iscoroutinefunction(func):
 
 
 def getlocation(function, curdir):
-    import inspect
     fn = py.path.local(inspect.getfile(function))
     lineno = py.builtin._getcode(function).co_firstlineno
     if fn.relto(curdir):
@@ -83,40 +87,45 @@ def num_mock_patch_args(function):
     return len(patchings)
 
 
-def getfuncargnames(function, startindex=None, cls=None):
-    """
-    @RonnyPfannschmidt: This function should be refactored when we revisit fixtures. The
-    fixture mechanism should ask the node for the fixture names, and not try to obtain
-    directly from the function object well after collection has occurred.
+def getfuncargnames(function, is_method=False, cls=None):
+    """Returns the names of a function's mandatory arguments.
+
+    This should return the names of all function arguments that:
+        * Aren't bound to an instance or type as in instance or class methods.
+        * Don't have default values.
+        * Aren't bound with functools.partial.
+        * Aren't replaced with mocks.
+
+    The is_method and cls arguments indicate that the function should
+    be treated as a bound method even though it's not unless, only in
+    the case of cls, the function is a static method.
+
+    @RonnyPfannschmidt: This function should be refactored when we
+    revisit fixtures. The fixture mechanism should ask the node for
+    the fixture names, and not try to obtain directly from the
+    function object well after collection has occurred.
+
     """
-    if startindex is None and cls is not None:
-        is_staticmethod = isinstance(cls.__dict__.get(function.__name__, None), staticmethod)
-        startindex = 0 if is_staticmethod else 1
-    # XXX merge with main.py's varnames
-    # assert not 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(_pytest._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(_pytest._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:])
+    # The parameters attribute of a Signature object contains an
+    # ordered mapping of parameter names to Parameter instances.  This
+    # creates a tuple of the names of the parameters that don't have
+    # defaults.
+    arg_names = tuple(
+        p.name for p in signature(function).parameters.values()
+        if (p.kind is Parameter.POSITIONAL_OR_KEYWORD
+            or p.kind is Parameter.KEYWORD_ONLY) and
+        p.default is Parameter.empty)
+    # If this function should be treated as a bound method even though
+    # it's passed as an unbound method or function, remove the first
+    # parameter name.
+    if (is_method or
+        (cls and not isinstance(cls.__dict__.get(function.__name__, None),
+                                staticmethod))):
+        arg_names = arg_names[1:]
+    # Remove any names that will be replaced with mocks.
+    if hasattr(function, "__wrapped__"):
+        arg_names = arg_names[num_mock_patch_args(function):]
+    return arg_names
 
 
 if _PY3:

_pytest/fixtures.py

@@ -728,8 +728,7 @@ def __init__(self, fixturemanager, baseid, argname, func, scope, params,
             where=baseid
         )
         self.params = params
-        startindex = unittest and 1 or None
-        self.argnames = getfuncargnames(func, startindex=startindex)
+        self.argnames = getfuncargnames(func, is_method=unittest)
         self.unittest = unittest
         self.ids = ids
         self._finalizer = []

changelog/2267.feature

@@ -0,0 +1,4 @@
+Replace the old introspection code in compat.py that determines the
+available arguments of fixtures with inspect.signature on Python 3 and
+funcsigs.signature on Python 2.  This should respect __signature__
+declarations on functions.

setup.py

@@ -44,16 +44,19 @@ def has_environment_marker_support():
 
 def main():
     install_requires = ['py>=1.4.34', 'six>=1.10.0', 'setuptools']
+    extras_require = {}
     # if _PYTEST_SETUP_SKIP_PLUGGY_DEP is set, skip installing pluggy;
     # used by tox.ini to test with pluggy master
     if '_PYTEST_SETUP_SKIP_PLUGGY_DEP' not in os.environ:
         install_requires.append('pluggy>=0.4.0,<0.5')
-    extras_require = {}
     if has_environment_marker_support():
+        extras_require[':python_version<"3.0"'] = ['funcsigs']
         extras_require[':sys_platform=="win32"'] = ['colorama']
     else:
         if sys.platform == 'win32':
             install_requires.append('colorama')
+        if sys.version_info < (3, 0):
+            install_requires.append('funcsigs')
 
     setup(
         name='pytest',

testing/python/fixture.py

@@ -2,7 +2,6 @@
 
 import _pytest._code
 import pytest
-import sys
 from _pytest.pytester import get_public_names
 from _pytest.fixtures import FixtureLookupError
 from _pytest import fixtures
@@ -34,9 +33,6 @@ def static(arg1, arg2):
             pass
 
     assert fixtures.getfuncargnames(A().f) == ('arg1',)
-    if sys.version_info < (3, 0):
-        assert fixtures.getfuncargnames(A.f) == ('arg1',)
-
     assert fixtures.getfuncargnames(A.static, cls=A) == ('arg1', 'arg2')
 
 
@@ -2826,7 +2822,7 @@ def test_show_fixtures_indented_in_class(self, testdir):
             import pytest
             class TestClass:
                 @pytest.fixture
-                def fixture1():
+                def fixture1(self):
                     """line1
                     line2
                         indented line