Emit a friendlier warning on invalid exclude regex, instead of a stacktrace

[wyattscarpenter]

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

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅