Use issubclass instead of isinstance to compare SourceGenerator in to_source

astor/code_gen.py

@@ -18,6 +18,7 @@
 """
 
 import ast
+import inspect
 import math
 import sys
 
@@ -53,10 +54,10 @@ class that will be instantiated and used to generate the source code.
     """
     if source_generator_class is None:
         source_generator_class = SourceGenerator
-    elif not isinstance(source_generator_class, SourceGenerator):
+    elif not inspect.isclass(source_generator_class):
+        raise TypeError('source_generator_class should be a class')
+    elif not issubclass(source_generator_class, SourceGenerator):
         raise TypeError('source_generator_class should be a subclass of SourceGenerator')
-    elif not callable(source_generator_class):
-        raise TypeError('source_generator_class should be a callable')
     generator = source_generator_class(
         indent_with, add_line_information, pretty_string)
     generator.visit(node)

docs/changelog.rst

@@ -15,6 +15,14 @@ Bug fixes
 .. _`Issue 153`: https://github.com/berkerpeksag/astor/issues/153
 .. _`PR 155`: https://github.com/berkerpeksag/astor/pull/155
 
+* Fixed :func:`astor.to_source` incorrectly checking whether
+  *source_generator_class* is a subclass of :class:`astor.code_gen.SourceGenerator`.
+  (Reported by Yu-Chia "Hank" Liu in `Issue 158`_ and fixed by Will Crichton in `PR 164`_.)
+
+.. _`Issue 158`: https://github.com/berkerpeksag/astor/issues/158
+.. _`PR 164`: https://github.com/berkerpeksag/astor/pull/164
+
+
 0.8.0 - 2019-05-19
 ------------------
 

tests/test_misc.py

@@ -66,7 +66,7 @@ class InvalidGenerator:
             )
         self.assertEqual(
             str(cm.exception),
-            'source_generator_class should be a callable',
+            'source_generator_class should be a class',
         )