Fix #4914: autodoc: Parsing error when using dataclasses without default values

CHANGES

@@ -33,6 +33,7 @@ Bugs fixed
 * #4978: latex: shorthandoff is not set up for Brazil locale
 * #4928: i18n: Ignore dot-directories like .git/ in LC_MESSAGES/
 * #4946: py domain: type field could not handle "None" as a type
+* #4914: autodoc: Parsing error when using dataclasses without default values
 
 Testing
 --------

sphinx/pycode/parser.py

@@ -224,12 +224,13 @@ class AfterCommentParser(TokenProcessor):
     def parse(self):
         # type: () -> None
         """Parse the code and obtain comment after assignment."""
-        # skip lvalue (until '=' operator)
-        while self.fetch_token() != [OP, '=']:
+        # skip lvalue (or whole of AnnAssign)
+        while not self.fetch_token().match([OP, '='], NEWLINE, COMMENT):
             assert self.current
 
-        # skip rvalue
-        self.fetch_rvalue()
+        # skip rvalue (if exists)
+        if self.current == [OP, '=']:
+            self.fetch_rvalue()
 
         if self.current == COMMENT:
             self.comment = self.current.value

tests/test_pycode_parser.py

@@ -100,11 +100,13 @@ def test_comment_picker_location():
 def test_annotated_assignment_py36():
     source = ('a: str = "Sphinx"  #: comment\n'
               'b: int = 1\n'
-              '"""string on next line"""')
+              '"""string on next line"""\n'
+              'c: int  #: comment')
     parser = Parser(source)
     parser.parse()
     assert parser.comments == {('', 'a'): 'comment',
-                               ('', 'b'): 'string on next line'}
+                               ('', 'b'): 'string on next line',
+                               ('', 'c'): 'comment'}
     assert parser.definitions == {}