Remove unnecessary parens around yield (#834)

black.py

@@ -2728,7 +2728,7 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
     for index, child in enumerate(list(node.children)):
         if check_lpar:
             if child.type == syms.atom:
-                if maybe_make_parens_invisible_in_atom(child):
+                if maybe_make_parens_invisible_in_atom(child, parent=node):
                     lpar = Leaf(token.LPAR, "")
                     rpar = Leaf(token.RPAR, "")
                     index = child.remove() or 0
@@ -2839,7 +2839,7 @@ def generate_ignored_nodes(leaf: Leaf) -> Iterator[LN]:
         container = container.next_sibling
 
 
-def maybe_make_parens_invisible_in_atom(node: LN) -> bool:
+def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
     """If it's safe, make the parens in the atom `node` invisible, recursively.
 
     Returns whether the node should itself be wrapped in invisible parentheses.
@@ -2849,7 +2849,7 @@ def maybe_make_parens_invisible_in_atom(node: LN) -> bool:
         node.type != syms.atom
         or is_empty_tuple(node)
         or is_one_tuple(node)
-        or is_yield(node)
+        or (is_yield(node) and parent.type != syms.expr_stmt)
         or max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
     ):
         return False
@@ -2861,7 +2861,7 @@ def maybe_make_parens_invisible_in_atom(node: LN) -> bool:
         first.value = ""  # type: ignore
         last.value = ""  # type: ignore
         if len(node.children) > 1:
-            maybe_make_parens_invisible_in_atom(node.children[1])
+            maybe_make_parens_invisible_in_atom(node.children[1], parent=parent)
         return False
 
     return True

tests/data/expression.diff

@@ -147,7 +147,7 @@
  slice[0:1:2]
  slice[:]
  slice[:-1]
-@@ -133,111 +156,169 @@
+@@ -133,113 +156,171 @@
  numpy[-(c + 1) :, d]
  numpy[:, l[-2]]
  numpy[:, ::-1]
@@ -214,9 +214,14 @@
 +
  def gen():
      yield from outside_of_generator
-     a = (yield)
- 
+-    a = (yield)
+-    b = ((yield))
+-    c = (((yield)))
++    a = yield
++    b = yield
++    c = yield
 +
+ 
  async def f():
      await some.complicated[0].call(with_args=(True or (1 is not 1)))
 -print(* [] or [1])

tests/data/expression.py

@@ -169,6 +169,8 @@
 def gen():
     yield from outside_of_generator
     a = (yield)
+    b = ((yield))
+    c = (((yield)))
 
 async def f():
     await some.complicated[0].call(with_args=(True or (1 is not 1)))
@@ -458,7 +460,9 @@ async def f():
 
 def gen():
     yield from outside_of_generator
-    a = (yield)
+    a = yield
+    b = yield
+    c = yield
 
 
 async def f():