fix bracket match bug (#470)

* fix bracket match bug

* add missing test file

black.py

@@ -877,8 +877,8 @@ class BracketTracker:
     bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = Factory(dict)
     delimiters: Dict[LeafID, Priority] = Factory(dict)
     previous: Optional[Leaf] = None
-    _for_loop_variable: int = 0
+    _for_loop_depths: List[int] = Factory(list)
-    _lambda_arguments: int = 0
+    _lambda_argument_depths: List[int] = Factory(list)
 
     def mark(self, leaf: Leaf) -> None:
         """Mark `leaf` with bracket-related metadata. Keep track of delimiters.
@@ -951,16 +951,21 @@ def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool:
         """
         if leaf.type == token.NAME and leaf.value == "for":
             self.depth += 1
-            self._for_loop_variable += 1
+            self._for_loop_depths.append(self.depth)
             return True
 
         return False
 
     def maybe_decrement_after_for_loop_variable(self, leaf: Leaf) -> bool:
         """See `maybe_increment_for_loop_variable` above for explanation."""
-        if self._for_loop_variable and leaf.type == token.NAME and leaf.value == "in":
+        if (
+            self._for_loop_depths
+            and self._for_loop_depths[-1] == self.depth
+            and leaf.type == token.NAME
+            and leaf.value == "in"
+        ):
             self.depth -= 1
-            self._for_loop_variable -= 1
+            self._for_loop_depths.pop()
             return True
 
         return False
@@ -973,16 +978,20 @@ def maybe_increment_lambda_arguments(self, leaf: Leaf) -> bool:
         """
         if leaf.type == token.NAME and leaf.value == "lambda":
             self.depth += 1
-            self._lambda_arguments += 1
+            self._lambda_argument_depths.append(self.depth)
             return True
 
         return False
 
     def maybe_decrement_after_lambda_arguments(self, leaf: Leaf) -> bool:
         """See `maybe_increment_lambda_arguments` above for explanation."""
-        if self._lambda_arguments and leaf.type == token.COLON:
+        if (
+            self._lambda_argument_depths
+            and self._lambda_argument_depths[-1] == self.depth
+            and leaf.type == token.COLON
+        ):
             self.depth -= 1
-            self._lambda_arguments -= 1
+            self._lambda_argument_depths.pop()
             return True
 
         return False

tests/data/bracketmatch.py

@@ -0,0 +1,15 @@
+for ((x in {}) or {})['a'] in x:
+    pass
+pem_spam = lambda l, spam = {
+    "x": 3
+}: not spam.get(l.strip())
+lambda x=lambda y={1: 3}: y['x':lambda y: {1: 2}]: x
+
+
+# output
+
+
+for ((x in {}) or {})["a"] in x:
+    pass
+pem_spam = lambda l, spam={"x": 3}: not spam.get(l.strip())
+lambda x=lambda y={1: 3}: y["x" : lambda y: {1: 2}]: x

tests/test_black.py

@@ -453,6 +453,14 @@ def test_new_line_between_class_and_code(self) -> None:
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
 
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_bracket_match(self) -> None:
+        source, expected = read_data("bracketmatch")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
     def test_report_verbose(self) -> None:
         report = black.Report(verbose=True)
         out_lines = []