Emit a friendlier warning on invalid exclude regex, instead of a stacktrace (#19102)

wyattscarpenter · pre-commit-ci[bot] · web-flow · commit 301c3b604a28 · 2025-05-19T07:25:57.000-07:00
If an invalid exclude is used, the error message ``` Traceback (most recent call last): File "<frozen runpy>", line 198, in _run_module_as_main File "<frozen runpy>", line 88, in _run_code File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\__main__.py", line 37, in <module> console_entry() File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\__main__.py", line 15, in console_entry main() File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\main.py", line 89, in main sources, options = process_options(args, stdout=stdout, stderr=stderr, fscache=fscache) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\main.py", line 1531, in process_options targets = create_source_list(special_opts.files, options, fscache) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\find_sources.py", line 48, in create_source_list sub_sources = finder.find_sources_in_dir(path) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\find_sources.py", line 121, in find_sources_in_dir if matches_exclude(subpath, self.exclude, self.fscache, self.verbosity >= 2): ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\files\gits\wyattscarpenter\!!! contributory forks\mypy\mypy\modulefinder.py", line 687, in matches_exclude if re.search(exclude, subpath_str): ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\__init__.py", line 177, in search return _compile(pattern, flags).search(string) ^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\__init__.py", line 307, in _compile p = _compiler.compile(pattern, flags) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\_compiler.py", line 750, in compile p = _parser.parse(p, flags) ^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\_parser.py", line 979, in parse p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\_parser.py", line 460, in _parse_sub itemsappend(_parse(source, state, verbose, nested + 1, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\_parser.py", line 544, in _parse code = _escape(source, this, state) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\wyatt\AppData\Local\Programs\Python\Python312\Lib\re\_parser.py", line 443, in _escape raise source.error("bad escape %s" % escape, len(escape)) re.error: bad escape \p at position 2 ``` now looks like this: ``` error: The exclude ..\publish is an invalid regular expression, because: bad escape \p at position 2 (Hint: use / as a path separator, even if you're on Windows!) For more information on Python's flavor of regex, see: https://docs.python.org/3/library/re.html ``` --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
diff --git a/mypy/modulefinder.py b/mypy/modulefinder.py
@@ -684,12 +684,27 @@ def matches_exclude(
     if fscache.isdir(subpath):
         subpath_str += "/"
     for exclude in excludes:
-        if re.search(exclude, subpath_str):
-            if verbose:
-                print(
-                    f"TRACE: Excluding {subpath_str} (matches pattern {exclude})", file=sys.stderr
+        try:
+            if re.search(exclude, subpath_str):
+                if verbose:
+                    print(
+                        f"TRACE: Excluding {subpath_str} (matches pattern {exclude})",
+                        file=sys.stderr,
+                    )
+                return True
+        except re.error as e:
+            print(
+                f"error: The exclude {exclude} is an invalid regular expression, because: {e}"
+                + (
+                    "\n(Hint: use / as a path separator, even if you're on Windows!)"
+                    if "\\" in exclude
+                    else ""
                 )
-            return True
+                + "\nFor more information on Python's flavor of regex, see:"
+                + " https://docs.python.org/3/library/re.html",
+                file=sys.stderr,
+            )
+            sys.exit(2)
     return False
 
 
@@ -786,7 +801,8 @@ def default_lib_path(
             print(
                 "error: --custom-typeshed-dir does not point to a valid typeshed ({})".format(
                     custom_typeshed_dir
-                )
+                ),
+                file=sys.stderr,
             )
             sys.exit(2)
     else:
