Prevent wrapping of multiline fstrings in parens (#4325)

src/black/linegen.py

@@ -37,6 +37,7 @@
     WHITESPACE,
     Visitor,
     ensure_visible,
+    fstring_to_string,
     get_annotation_type,
     is_arith_like,
     is_async_stmt_or_funcdef,
@@ -504,7 +505,7 @@ def visit_NUMBER(self, leaf: Leaf) -> Iterator[Line]:
 
     def visit_fstring(self, node: Node) -> Iterator[Line]:
         # currently we don't want to format and split f-strings at all.
-        string_leaf = _fstring_to_string(node)
+        string_leaf = fstring_to_string(node)
         node.replace(string_leaf)
         yield from self.visit_STRING(string_leaf)
 
@@ -574,12 +575,6 @@ def __post_init__(self) -> None:
             self.visit_guard = partial(v, keywords=Ø, parens={"if"})
 
 
-def _fstring_to_string(node: Node) -> Leaf:
-    """Converts an fstring node back to a string node."""
-    string_without_prefix = str(node)[len(node.prefix) :]
-    return Leaf(token.STRING, string_without_prefix, prefix=node.prefix)
-
-
 def _hugging_power_ops_line_to_string(
     line: Line,
     features: Collection[Feature],
@@ -1421,7 +1416,7 @@ def normalize_invisible_parens(  # noqa: C901
                 # of case will be not parsed as a Python keyword.
                 break
 
-            elif not (isinstance(child, Leaf) and is_multiline_string(child)):
+            elif not is_multiline_string(child):
                 wrap_in_parentheses(node, child, visible=False)
 
         comma_check = child.type == token.COMMA

src/black/nodes.py

@@ -762,8 +762,28 @@ def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
     return p.type in within
 
 
-def is_multiline_string(leaf: Leaf) -> bool:
+def is_fstring(node: Node) -> bool:
+    """Return True if the node is an f-string"""
+    return node.type == syms.fstring
+
+
+def fstring_to_string(node: Node) -> Leaf:
+    """Converts an fstring node back to a string node."""
+    string_without_prefix = str(node)[len(node.prefix) :]
+    string_leaf = Leaf(token.STRING, string_without_prefix, prefix=node.prefix)
+    string_leaf.lineno = node.get_lineno() or 0
+    return string_leaf
+
+
+def is_multiline_string(node: LN) -> bool:
     """Return True if `leaf` is a multiline string that actually spans many lines."""
+    if isinstance(node, Node) and is_fstring(node):
+        leaf = fstring_to_string(node)
+    elif isinstance(node, Leaf):
+        leaf = node
+    else:
+        return False
+
     return has_triple_quotes(leaf.value) and "\n" in leaf.value
 
 

tests/data/cases/pep_701.py

@@ -110,6 +110,15 @@
     {1}_cte AS ()'''}
 """
 
+value: str = f'''foo
+'''
+
+log(
+    f"Received operation {server_operation.name} from "
+    f"{self.writer._transport.get_extra_info('peername')}",  # type: ignore[attr-defined]
+    level=0,
+)
+
 # output
 
 x = f"foo"
@@ -222,3 +231,12 @@
     WITH {f'''
     {1}_cte AS ()'''}
 """
+
+value: str = f"""foo
+"""
+
+log(
+    f"Received operation {server_operation.name} from "
+    f"{self.writer._transport.get_extra_info('peername')}",  # type: ignore[attr-defined]
+    level=0,
+)