Refactor re-parsing into recursive func (python#15678)

The reparse function could be expanded upon to tweak the source and
parse it again to handle any number of exceptions bases on options.

This formulation also preserves the original exception and raises it if
the source can't eventually be successfully parsed.

mypy/fastparse.py

@@ -4,7 +4,7 @@
 import re
 import sys
 import warnings
-from typing import Any, Callable, Final, List, Optional, Sequence, TypeVar, Union, cast
+from typing import Any, AnyStr, Callable, Final, List, Optional, Sequence, TypeVar, Union, cast
 from typing_extensions import Literal, overload
 
 from mypy import defaults, errorcodes as codes, message_registry
@@ -181,6 +181,47 @@ def ast3_parse(
 TYPE_COMMENT_PATTERN: Final = re.compile(r"([^#]*)(#\s*type:.*)")
 
 
+def _ast_reparse(
+ source: str | bytes | AnyStr,
+ fnam: str,
+ feature_version: int,
+ options: Options,
+ errors: Errors,
+ original_exc: Exception | None = None,
+) -> AST:
+ try:
+ return ast3_parse(source, fnam, "exec", feature_version=feature_version)
+ except SyntaxError as e:
+
+ def strip_comment(line: AnyStr) -> AnyStr:
+ if isinstance(line, str):
+ return re.sub(r"([^#]*).*(\r\n|\r|\n)?", r"\1\2", line)
+ return re.sub(rb"([^#]*).*(\r\n|\r|\n)?", rb"\1\2", line)
+
+ def strip_comment_from_line(text: AnyStr, target_lineno: int) -> AnyStr:
+ return type(text)().join(
+ line if lineno != target_lineno else strip_comment(line)
+ for lineno, line in enumerate(text.splitlines(keepends=True), start=1)
+ )
+
+ ignore_comment_errors = options.ignore_comment_errors
+ if ignore_comment_errors and e.text and e.lineno and TYPE_COMMENT_PATTERN.match(e.text):
+ errors.report(
+ e.lineno or -1,
+ e.offset or -1,
+ f"Ignored bad type comment: {e.text.strip()}",
+ severity="note",
+ code=codes.SYNTAX,
+ )
+ stripped_source = strip_comment_from_line(cast(AnyStr, source), e.lineno)
+ if stripped_source == source: # check to prevent infinite recursion
+ raise original_exc or e from None
+ return _ast_reparse(
+ stripped_source, fnam, feature_version, options, errors, original_exc or e
+ )
+ raise original_exc or e from None
+
+
 def parse(
  source: str | bytes,
  fnam: str,
@@ -214,58 +255,10 @@ def parse(
  assert options.python_version[0] >= 3
  feature_version = options.python_version[1]
  try:
- ignore_comment_errors = options.ignore_comment_errors
-
- def try_parse_ast(source: str | bytes) -> tuple[AST | None, str | bytes]:
- try:
- ast = ast3_parse(source, fnam, "exec", feature_version=feature_version)
- except SyntaxError as e:
-
- def strip_comment(line: str) -> str:
- return re.sub(r"([^#]*).*(\r\n|\r|\n)?", r"\1\2", line)
-
- def strip_commentb(line: bytes) -> bytes:
- return re.sub(rb"([^#]*).*(\r\n|\r|\n)?", rb"\1\2", line)
-
- def strip_comment_from_line(text: str | bytes, target_lineno: int) -> str | bytes:
- if isinstance(text, str):
- return "".join(
- line if lineno != target_lineno else strip_comment(line)
- for lineno, line in enumerate(text.splitlines(keepends=True), start=1)
- )
- return b"".join(
- line if lineno != target_lineno else strip_commentb(line)
- for lineno, line in enumerate(text.splitlines(keepends=True), start=1)
- )
-
- if (
- ignore_comment_errors
- and e.text
- and e.lineno
- and TYPE_COMMENT_PATTERN.match(e.text)
- ):
- stripped_source = strip_comment_from_line(source, e.lineno)
- errors.report(
- e.lineno or -1,
- e.offset or -1,
- f"Ignored bad type comment: {e.text.strip()}",
- severity="note",
- code=codes.SYNTAX,
- )
- return None, stripped_source
- raise
- return ast, source
-
  # Disable deprecation warnings about \u
  with warnings.catch_warnings():
  warnings.filterwarnings("ignore", category=DeprecationWarning)
- ast: AST | None = None
- next_source = source
- # The source will be parsed n + 1 times, where n is the number of malformed type
- # comments in the source. While potentially expensive, source files with a large
- # number of malformed comments should be rare.
- while not ast:
- ast, next_source = try_parse_ast(next_source)
+ ast = _ast_reparse(source, fnam, feature_version, options, errors)
 
  tree = ASTConverter(
  options=options,