Merge lp:~cjwatson/storm/py3-mocker-inspect into lp:storm

[Colin Watson]

Add Python 3 support to tests.mocker.SpecChecker.

inspect.getargspec is deprecated on Python 3, and in any case causes us problems because it includes the bound first argument (self or similar) for bound methods. The modern inspect.signature API is for the most part much easier to use and doesn't have this problem.

There is one wrinkle which requires special handling: method descriptors don't have the first argument already bound as far as their signature is concerned, but for the purposes of a mock spec we want to skip it anyway.

[Simon Poirier (simpoir)]

+1 Not the prettiest change, but seems ok.

review: Approve

[lp:~cjwatson/storm/py3-mocker-inspect]

513. By Colin Watson on 2019-08-21

Explain positional-only test.

=== modified file 'storm/tests/mocker.py'
--- storm/tests/mocker.py	2019-08-21 09:40:30 +0000
+++ storm/tests/mocker.py	2019-08-21 11:14:10 +0000
@@ -1830,22 +1830,43 @@
 
         if method:
             try:
-                self._args, self._varargs, self._varkwargs, self._defaults = \
-                    inspect.getargspec(method)
+                if six.PY3:
+                    # On Python 3, inspect.getargspec includes the bound
+                    # first argument (self or similar) for bound methods,
+                    # which confuses matters.  The modern signature API
+                    # doesn't have this problem.
+                    self._signature = inspect.signature(method)
+                    # Method descriptors don't have the first argument
+                    # already bound, but we want to skip it anyway.
+                    if getattr(method, "__objclass__", None) is not None:
+                        parameters = list(self._signature.parameters.values())
+                        # This is positional-only for unbound methods that
+                        # are implemented in C.
+                        if (parameters[0].kind ==
+                                inspect.Parameter.POSITIONAL_ONLY):
+                            self._signature = self._signature.replace(
+                                parameters=parameters[1:])
+                else:
+                    (self._args, self._varargs, self._varkwargs,
+                     self._defaults) = inspect.getargspec(method)
             except TypeError:
                 self._unsupported = True
             else:
-                if self._defaults is None:
-                    self._defaults = ()
-                if type(method) is type(self.run):
-                    self._args = self._args[1:]
+                if not six.PY3:
+                    if self._defaults is None:
+                        self._defaults = ()
+                    if type(method) is type(self.run):
+                        self._args = self._args[1:]
 
     def get_method(self):
         return self._method
 
     def _raise(self, message):
-        spec = inspect.formatargspec(self._args, self._varargs,
-                                     self._varkwargs, self._defaults)
+        if six.PY3:
+            spec = str(self._signature)
+        else:
+            spec = inspect.formatargspec(self._args, self._varargs,
+                                         self._varkwargs, self._defaults)
         raise AssertionError("Specification is %s%s: %s" %
                              (self._method.__name__, spec, message))
 
@@ -1866,20 +1887,26 @@
         if self._unsupported:
             return # Can't check it. Happens with builtin functions. :-(
         action = path.actions[-1]
-        obtained_len = len(action.args)
-        obtained_kwargs = action.kwargs.copy()
-        nodefaults_len = len(self._args) - len(self._defaults)
-        for i, name in enumerate(self._args):
-            if i < obtained_len and name in action.kwargs:
-                self._raise("%r provided twice" % name)
-            if (i >= obtained_len and i < nodefaults_len and
-                name not in action.kwargs):
-                self._raise("%r not provided" % name)
-            obtained_kwargs.pop(name, None)
-        if obtained_len > len(self._args) and not self._varargs:
-            self._raise("too many args provided")
-        if obtained_kwargs and not self._varkwargs:
-            self._raise("unknown kwargs: %s" % ", ".join(obtained_kwargs))
+        if six.PY3:
+            try:
+                self._signature.bind(*action.args, **action.kwargs)
+            except TypeError as e:
+                self._raise(str(e))
+        else:
+            obtained_len = len(action.args)
+            obtained_kwargs = action.kwargs.copy()
+            nodefaults_len = len(self._args) - len(self._defaults)
+            for i, name in enumerate(self._args):
+                if i < obtained_len and name in action.kwargs:
+                    self._raise("%r provided twice" % name)
+                if (i >= obtained_len and i < nodefaults_len and
+                    name not in action.kwargs):
+                    self._raise("%r not provided" % name)
+                obtained_kwargs.pop(name, None)
+            if obtained_len > len(self._args) and not self._varargs:
+                self._raise("too many args provided")
+            if obtained_kwargs and not self._varkwargs:
+                self._raise("unknown kwargs: %s" % ", ".join(obtained_kwargs))
 
 def spec_checker_recorder(mocker, event):
     spec = event.path.root_mock.__mocker_spec__