Include underlying error when AST safety check parsing fails (#2693)

diff --git a/CHANGES.md b/CHANGES.md
index c73295c4a0dad077a8fb0503135eb5ca6c063099..9208be7cd968e2997e9478ff71a24ef99bcf5e0a 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,6 +5,8 @@
 ### _Black_
 
 - Improve error message for invalid regular expression (#2678)
+- Improve error message when parsing fails during AST safety check by embedding the
+  underlying SyntaxError (#2693)
 - Fix mapping cases that contain as-expressions, like `case {"key": 1 | 2 as password}`
   (#2686)
 - No longer color diff headers white as it's unreadable in light themed terminals

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 59018d00de469c5e276a98f84cca506e44c29d80..f2efdec83b22a53d1ad00f6d1b1057dcae1f0c0f 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1305,7 +1305,7 @@ def assert_equivalent(src: str, dst: str, *, pass_num: int = 1) -> None:
         src_ast = parse_ast(src)
     except Exception as exc:
         raise AssertionError(
-            "cannot use --safe with this file; failed to parse source file."
+            f"cannot use --safe with this file; failed to parse source file: {exc}"
         ) from exc
 
     try:

diff --git a/tests/test_black.py b/tests/test_black.py
index 468f00fcafb82c43a2cca3677cec918f3518b5f3..63cd716c0bb80aeea9cf31c274ead6b1b930d4e6 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1584,6 +1584,16 @@ class BlackTestCase(BlackBaseTestCase):
 
         exc_info.match("Cannot parse: 2:0: EOF in multi-line statement")
 
+    def test_equivalency_ast_parse_failure_includes_error(self) -> None:
+        with pytest.raises(AssertionError) as err:
+            black.assert_equivalent("a«»a  = 1", "a«»a  = 1")
+
+        err.match("--safe")
+        # Unfortunately the SyntaxError message has changed in newer versions so we
+        # can't match it directly.
+        err.match("invalid character")
+        err.match(r"\(<unknown>, line 1\)")
+
 
 class TestCaching:
     def test_cache_broken_file(self) -> None: