Merge pull request #582 from kmike/inspect-workaround

[WIP] Handle cases when inspect.stack() fails

scrapy/tests/test_utils_deprecate.py

@@ -3,14 +3,18 @@ from __future__ import absolute_import
 import inspect
 import unittest
 import warnings
+import mock
 from scrapy.utils.deprecate import create_deprecated_class
 
+
 class MyWarning(UserWarning):
     pass
 
+
 class SomeBaseClass(object):
     pass
 
+
 class NewName(SomeBaseClass):
     pass
 
@@ -234,3 +238,12 @@ class WarnWhenSubclassedTest(unittest.TestCase):
         self.assertIn('foo.Bar', str(w[0].message))
         self.assertIn('AlsoDeprecated', str(w[1].message))
         self.assertIn('foo.Bar', str(w[1].message))
+
+    def test_inspect_stack(self):
+        with mock.patch('inspect.stack', side_effect=IndexError):
+            with warnings.catch_warnings(record=True) as w:
+                DeprecatedName = create_deprecated_class('DeprecatedName', NewName)
+                class SubClass(DeprecatedName):
+                    pass
+
+        self.assertIn("Error detecting parent module", str(w[0].message))

scrapy/utils/deprecate.py

@@ -101,10 +101,18 @@ def create_deprecated_class(name, new_class, clsdict=None,
             return super(DeprecatedClass, cls).__call__(*args, **kwargs)
 
     deprecated_cls = DeprecatedClass(name, (new_class,), clsdict or {})
-    frm = inspect.stack()[1]
-    parent_module = inspect.getmodule(frm[0])
-    if parent_module is not None:
-        deprecated_cls.__module__ = parent_module.__name__
+
+    try:
+        frm = inspect.stack()[1]
+        parent_module = inspect.getmodule(frm[0])
+        if parent_module is not None:
+            deprecated_cls.__module__ = parent_module.__name__
+    except Exception as e:
+        # Sometimes inspect.stack() fails (e.g. when the first import of
+        # deprecated class is in jinja2 template). __module__ attribute is not
+        # important enough to raise an exception as users may be unable
+        # to fix inspect.stack() errors.
+        warnings.warn("Error detecting parent module: %r" % e)
 
     return deprecated_cls