ext.autodoc: fix formatting instance annotations

Currently `format_annotation` fails on instances, because instances don't have
`__module__` and `__qualname__` attributes.  Defer building the
`qualified_name` of an annotation until we have established that the annotation
is a type.

CHANGES

@@ -15,6 +15,7 @@ Bugs fixed
 * #2778: Fix autodoc crashes if obj.__dict__ is a property method and raises exception
 * Fix duplicated toc in epub3 output.
 * #2775: Fix failing linkcheck with servers not supporting identidy encoding
+* #2833: Fix formatting instance annotations in ext.autodoc.
 
 Release 1.4.5 (released Jul 13, 2016)
 =====================================

sphinx/ext/autodoc.py

@@ -261,12 +261,13 @@ def format_annotation(annotation):
 
     Displaying complex types from ``typing`` relies on its private API.
     """
+    if not isinstance(annotation, type):
+        return repr(annotation)
+
     qualified_name = (annotation.__module__ + '.' + annotation.__qualname__
                       if annotation else repr(annotation))
 
-    if not isinstance(annotation, type):
-        return repr(annotation)
-    elif annotation.__module__ == 'builtins':
+    if annotation.__module__ == 'builtins':
         return annotation.__qualname__
     elif typing:
         if isinstance(annotation, typing.TypeVar):

tests/test_autodoc.py

@@ -1025,7 +1025,7 @@ def test_type_hints():
     from sphinx.util.inspect import getargspec
 
     try:
-        from typing_test_data import f0, f1, f2, f3, f4, f5, f6, f7, f8
+        from typing_test_data import f0, f1, f2, f3, f4, f5, f6, f7, f8, f9
     except (ImportError, SyntaxError):
         raise SkipTest('Cannot import Python code with function annotations')
 
@@ -1061,3 +1061,6 @@ def test_type_hints():
     # Tuple types
     verify_arg_spec(f8, '(x: typing.Tuple[int, str],'
                         ' y: typing.Tuple[int, ...]) -> None')
+
+    # Instance annotations
+    verify_arg_spec(f9, '(x: CustomAnnotation, y: 123) -> None')

tests/typing_test_data.py

@@ -46,3 +46,11 @@ def f7(x: Callable[[int, str], int]) -> None:
 
 def f8(x: Tuple[int, str], y: Tuple[int, ...]) -> None:
     pass
+
+
+class CustomAnnotation:
+    def __repr__(self):
+        return 'CustomAnnotation'
+
+def f9(x: CustomAnnotation(), y: 123) -> None:
+    pass