Keep type annotations intact if possible

CHANGELOG

@@ -2,7 +2,10 @@
 # All notable changes to this project will be documented in this file.
 # This project adheres to [Semantic Versioning](http://semver.org/).
 
-## [0.14.1] UNRELEASED
+## [0.15.0] 2017-01-12
+### Added
+- Keep type annotations intact as much as possible. Don't try to split the over
+  mutliple lines.
 ### Fixed
 - When determining if each element in a dictionary can fit on a single line, we
   are skipping dictionary entries. However, we need to ignore comments in our
@@ -12,7 +15,7 @@
 - Also allow text before a "yapf: (disable|enable)" comment.
 
 ## [0.14.0] 2016-11-21
-#### Added
+### Added
 - formatting can be run in parallel using the "-p" / "--parallel" flags.
 ### Fixed
 - "not in" and "is not" should be subtyped as binary operators.

yapf/yapflib/split_penalty.py

@@ -82,13 +82,22 @@ def Visit_funcdef(self, node):  # pylint: disable=invalid-name
     while pytree_utils.NodeName(node.children[colon_idx]) == 'simple_stmt':
       colon_idx += 1
     self._SetUnbreakable(node.children[colon_idx])
+    arrow_idx = -1
     while colon_idx < len(node.children):
-      if (isinstance(node.children[colon_idx], pytree.Leaf) and
-          node.children[colon_idx].value == ':'):
-        break
+      if isinstance(node.children[colon_idx], pytree.Leaf):
+        if node.children[colon_idx].value == ':':
+          break
+        if node.children[colon_idx].value == '->':
+          arrow_idx = colon_idx
       colon_idx += 1
     self._SetUnbreakable(node.children[colon_idx])
     self.DefaultNodeVisit(node)
+    if arrow_idx > 0:
+      pytree_utils.SetNodeAnnotation(
+          _LastChildNode(node.children[arrow_idx - 1]),
+          pytree_utils.Annotation.SPLIT_PENALTY, 0)
+      self._SetUnbreakable(node.children[arrow_idx])
+      self._SetStronglyConnected(node.children[arrow_idx + 1])
 
   def Visit_lambdef(self, node):  # pylint: disable=invalid-name
     # lambdef ::= 'lambda' [varargslist] ':' test
@@ -317,7 +326,7 @@ def _SetUnbreakableOnChildren(self, node):
       self._SetUnbreakable(node.children[i])
 
   def _SetExpressionPenalty(self, node, penalty):
-    """Set an ARITHMETIC_EXPRESSION penalty annotation children nodes."""
+    """Set a penalty annotation on children nodes."""
 
     def RecArithmeticExpression(node, first_child_leaf):
       if node is first_child_leaf:

yapf/yapflib/subtype_assigner.py

@@ -83,7 +83,8 @@ def Visit_dictsetmaker(self, node):  # pylint: disable=invalid-name
       for child in node.children:
         if dict_maker:
           if pytree_utils.NodeName(child) == 'DOUBLESTAR':
-            _AppendFirstLeafTokenSubtype(child, format_token.Subtype.KWARGS_STAR_STAR)
+            _AppendFirstLeafTokenSubtype(child,
+                                         format_token.Subtype.KWARGS_STAR_STAR)
           if last_was_colon:
             if style.Get('INDENT_DICTIONARY_VALUE'):
               _InsertPseudoParentheses(child)

yapftests/reformatter_python3_test.py

@@ -179,6 +179,24 @@ async def foo():
     uwlines = yapf_test_helper.ParseAndUnwrap(unformatted_code)
     self.assertCodeEqual(expected_formatted_code, reformatter.Reformat(uwlines))
 
+  def testKeepTypesIntact(self):
+    if sys.version_info[1] < 5:
+      return
+    unformatted_code = textwrap.dedent("""\
+        def _ReduceAbstractContainers(
+            self, *args: Optional[automation_converter.PyiCollectionAbc]) -> List[
+                automation_converter.PyiCollectionAbc]:
+            pass
+        """)
+    expected_formatted_code = textwrap.dedent("""\
+        def _ReduceAbstractContainers(
+                self, *args: Optional[automation_converter.PyiCollectionAbc]
+        ) -> List[automation_converter.PyiCollectionAbc]:
+            pass
+        """)
+    uwlines = yapf_test_helper.ParseAndUnwrap(unformatted_code)
+    self.assertCodeEqual(expected_formatted_code, reformatter.Reformat(uwlines))
+
 
 if __name__ == '__main__':
   unittest.main()