Share more code between the warn() and fail() branches

Lib/test/test_clinic.py

@@ -1446,8 +1446,12 @@ def test_non_ascii_character_in_docstring(self):
             self.parse(block)
         # The line numbers are off; this is a known limitation.
         expected = dedent("""\
-            Warning on line 0: Non-ascii characters are not allowed in docstrings: 'á'
-            Warning on line 0: Non-ascii characters are not allowed in docstrings: 'ü', 'á', 'ß'
+            Warning on line 0:
+            Non-ascii characters are not allowed in docstrings: 'á'
+
+            Warning on line 0:
+            Non-ascii characters are not allowed in docstrings: 'ü', 'á', 'ß'
+
         """)
         self.assertEqual(stdout.getvalue(), expected)
 

Tools/clinic/clinic.py

@@ -137,18 +137,25 @@ def text_accumulator() -> TextAccumulator:
     return TextAccumulator(append, output)
 
 
+@dc.dataclass
 class ClinicError(Exception):
-    def __init__(
-        self,
-        message: str,
-        /,
-        *,
-        lineno: int | None = None,
-        filename: str | None = None
-    ) -> None:
-        super().__init__(message)
-        self.lineno = lineno
-        self.filename = filename
+    message: str
+    _: dc.KW_ONLY
+    lineno: int | None = None
+    filename: str | None = None
+
+    def __post_init__(self) -> None:
+        super().__init__(self.message)
+
+    def report(self, *, warn_only: bool = False) -> str:
+        msg = "Warning" if warn_only else "Error"
+        if self.filename is not None:
+            msg += f" in file {self.filename!r}"
+        if self.lineno is not None:
+            msg += f" on line {self.lineno}"
+        msg += ":\n"
+        msg += f"{self.message}\n"
+        return msg
 
 
 @overload
@@ -179,16 +186,11 @@ def warn_or_fail(
             filename = clinic.filename
         if getattr(clinic, 'block_parser', None) and (line_number is None):
             line_number = clinic.block_parser.line_number
+    error = ClinicError(joined, filename=filename, lineno=line_number)
     if fail:
-        raise ClinicError(joined, lineno=line_number, filename=filename)
+        raise error
     else:
-        msg = "Warning"
-        if filename is not None:
-            msg += f" in file {filename!r}"
-        if line_number is not None:
-            msg += f" on line {line_number}"
-        msg += f": {joined}"
-        print(msg)
+        print(error.report(warn_only=True))
 
 
 def warn(
@@ -5734,13 +5736,7 @@ def main(argv: list[str] | None = None) -> NoReturn:
     try:
         run_clinic(parser, args)
     except ClinicError as exc:
-        sys.stderr.write("Error")
-        if exc.filename is not None:
-            sys.stderr.write(f" in file {exc.filename!r}")
-        if exc.lineno is not None:
-            sys.stderr.write(f" on line {exc.lineno}")
-        sys.stderr.write(":\n")
-        sys.stderr.write(f"{exc}\n")
+        sys.stderr.write(exc.report())
         sys.exit(1)
     else:
         sys.exit(0)