only mention target version

CHANGES.md

@@ -46,8 +46,7 @@
 ### Output
 
 <!-- Changes to Black's terminal output and error messages -->
-
-- Added Python and grammar version information to a parsing error message (#4378)
+- Added Python target version information on parse error (#4378)
 
 ### _Blackd_
 

docs/usage_and_configuration/the_basics.md

@@ -427,7 +427,7 @@ plus a short summary.
 
 ```console
 $ black src/
-error: cannot format src/black_primer/cli.py: Cannot parse: The assigned grammars (3.0, 3.7) for your Python versions (PY33, PY39) all failed to parse: 5:6: mport asyncio
+error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
 reformatted src/black_primer/lib.py
 reformatted src/blackd/__init__.py
 reformatted src/black/__init__.py

src/black/mode.py

@@ -26,6 +26,10 @@ class TargetVersion(Enum):
     PY312 = 12
     PY313 = 13
 
+    def pretty(self) -> str:
+        assert self.name[:2] == "PY"
+        return f"Python {self.name[2]}.{self.name[3:]}"
+
 
 class Feature(Enum):
     F_STRINGS = 2

src/black/parsing.py

@@ -5,7 +5,7 @@
 import ast
 import sys
 import warnings
-from typing import Iterable, Iterator, List, Set, Tuple
+from typing import Collection, Iterator, List, Set, Tuple
 
 from black.mode import VERSION_TO_FEATURES, Feature, TargetVersion, supports_feature
 from black.nodes import syms
@@ -52,21 +52,19 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
     return grammars
 
 
-def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:
+def lib2to3_parse(
+    src_txt: str, target_versions: Collection[TargetVersion] = ()
+) -> Node:
     """Given a string with source, return the lib2to3 Node."""
     if not src_txt.endswith("\n"):
         src_txt += "\n"
 
     grammars = get_grammars(set(target_versions))
-
-    version_names = [version.name for version in target_versions]
-    grammar_names = [
-        f"{grammar.version[0]}.{grammar.version[1]}" for grammar in grammars
-    ]
-    error_string = (
-        f"The assigned grammars ({', '.join(sorted(grammar_names))}) for your Python"
-        f" versions ({', '.join(sorted(version_names))}) all failed to parse"
-    )
+    if target_versions:
+        max_tv = max(target_versions, key=lambda tv: tv.value)
+        tv_str = f" for target version {max_tv.pretty()}"
+    else:
+        tv_str = ""
 
     errors = {}
     for grammar in grammars:
@@ -83,14 +81,14 @@ def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -
             except IndexError:
                 faulty_line = "<line number missing in source>"
             errors[grammar.version] = InvalidInput(
-                f"Cannot parse: {error_string} line: {lineno}:{column}: {faulty_line}"
+                f"Cannot parse{tv_str}: {lineno}:{column}: {faulty_line}"
             )
 
         except TokenError as te:
             # In edge cases these are raised; and typically don't have a "faulty_line".
             lineno, column = te.args[1]
             errors[grammar.version] = InvalidInput(
-                f"Cannot parse: {error_string}: {lineno}:{column}: {te.args[0]}"
+                f"Cannot parse{tv_str}: {lineno}:{column}: {te.args[0]}"
             )
 
     else:

tests/test_black.py

@@ -1034,11 +1034,7 @@ def test_format_file_contents(self) -> None:
         invalid = "return if you can"
         with self.assertRaises(black.InvalidInput) as e:
             black.format_file_contents(invalid, mode=mode, fast=False)
-        self.assertRegex(
-            str(e.exception),
-            r"Cannot parse: The assigned grammars \((.*?)\) for your Python versions"
-            r" \((.*?)\) all failed to parse line: 1:7: return if you can",
-        )
+        self.assertEqual(str(e.exception), "Cannot parse: 1:7: return if you can")
 
         just_crlf = "\r\n"
         with self.assertRaises(black.NothingChanged):
@@ -1988,10 +1984,7 @@ def test_for_handled_unexpected_eof_error(self) -> None:
         with pytest.raises(black.parsing.InvalidInput) as exc_info:
             black.lib2to3_parse("print(", {})
 
-        exc_info.match(
-            r"Cannot parse: The assigned grammars \((.*?)\) for your Python versions"
-            r" \((.*?)\) all failed to parse: 2:0: EOF in multi-line statement"
-        )
+        exc_info.match("Cannot parse: 2:0: EOF in multi-line statement")
 
     def test_line_ranges_with_code_option(self) -> None:
         code = textwrap.dedent("""\

tests/test_format.py

@@ -87,7 +87,4 @@ def test_patma_invalid() -> None:
     with pytest.raises(black.parsing.InvalidInput) as exc_info:
         assert_format(source, expected, mode, minimum_version=(3, 10))
 
-    exc_info.match(
-        "Cannot parse: The assigned grammars \\(3.10\\) for your Python versions"
-        " \\(PY310\\) all failed to parse line: 10:11:     case a := b:"
-    )
+    exc_info.match("Cannot parse for target version Python 3.10: 10:11:     case a := b:")