be more strict, but also more lenient, about error code comment format

Author: wyattscarpenter

mypy/test/data.py

@@ -533,9 +533,9 @@ def expand_errors(input: list[str], output: list[str], fnam: str) -> None:
 
     for i in range(len(input)):
         # The first in the split things isn't a comment
-        for possible_err_comment in re.split(r"(?!\\)#", input[i])[1:]:
+        for possible_err_comment in re.split(r"(?!\\)#\s*(?=[ENW]\s*:)", input[i])[1:]:
             m = re.search(
-                r"^([ENW]):((?P<col>\d+):)? (?P<message>.*)$", possible_err_comment.strip()
+                r"^([ENW])\s*:((?P<col>\d+):)?\s*(?P<message>.*)$", possible_err_comment.strip()
             )
             if m:
                 if m.group(1) == "E":

mypy/test/update_data.py

@@ -64,7 +64,7 @@ def _iter_fixes(
         fix_lines = []
         for lineno, source_line in enumerate(source_lines, start=1):
             reports = reports_by_line.get((file_path, lineno))
-            comment_match = re.search(r"(?P<indent>\s+)(?P<comment># ?[EWN]: .+)$", source_line)
+            comment_match = re.search(r"(?P<indent>\s+)(?P<comment>#\s*[EWN]\s*:.+)$", source_line)
             if comment_match:
                 source_line = source_line[: comment_match.start("indent")]  # strip old comment
             if reports: