fix error message for match (psf#2649)

JelleZijlstra · isidentical · web-flow · commit 0f7cf9187f9c · 2021-11-30T18:39:39.000-08:00
Fixes psf#2648. Co-authored-by: Batuhan Taskaya <isidentical@gmail.com>
diff --git a/CHANGES.md b/CHANGES.md
@@ -15,6 +15,7 @@
   times, like `match re.match()` (#2661)
 - Fix assignment to environment variables in Jupyter Notebooks (#2642)
 - Add `flake8-simplify` and `flake8-comprehensions` plugins (#2653)
+- Fix parser error location on invalid syntax in a `match` statement (#2649)
 
 ## 21.11b1
 
diff --git a/src/black/parsing.py b/src/black/parsing.py
@@ -75,8 +75,10 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
         # Python 3.10+
         grammars.append(pygram.python_grammar_soft_keywords)
     # If we have to parse both, try to parse async as a keyword first
-    if not supports_feature(target_versions, Feature.ASYNC_IDENTIFIERS):
-        # Python 3.7+
+    if not supports_feature(
+        target_versions, Feature.ASYNC_IDENTIFIERS
+    ) and not supports_feature(target_versions, Feature.PATTERN_MATCHING):
+        # Python 3.7-3.9
         grammars.append(
             pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords
         )
diff --git a/tests/data/pattern_matching_invalid.py b/tests/data/pattern_matching_invalid.py
@@ -0,0 +1,18 @@
+# First match, no errors
+match something:
+    case bla():
+        pass
+
+# Problem on line 10
+match invalid_case:
+    case valid_case:
+        pass
+    case a := b:
+        pass
+    case valid_case:
+        pass
+
+# No problems either
+match something:
+    case bla():
+        pass
diff --git a/tests/test_format.py b/tests/test_format.py
@@ -200,6 +200,15 @@ def test_python_310(filename: str) -> None:
     assert_format(source, expected, mode, minimum_version=(3, 10))
 
 
+def test_patma_invalid() -> None:
+    source, expected = read_data("pattern_matching_invalid")
+    mode = black.Mode(target_versions={black.TargetVersion.PY310})
+    with pytest.raises(black.parsing.InvalidInput) as exc_info:
+        assert_format(source, expected, mode, minimum_version=(3, 10))
+
+    exc_info.match("Cannot parse: 10:11")
+
+
 def test_docstring_no_string_normalization() -> None:
     """Like test_docstring but with string normalization off."""
     source, expected = read_data("docstring_no_string_normalization")
