♻️ Refactor header option parser to use the standard library instead of a custom RegEx (#75)

Author: tiangolo

multipart/multipart.py

@@ -9,6 +9,8 @@
 import tempfile
 from io import BytesIO
 from numbers import Number
+from email.message import Message
+from typing import Dict, Union, Tuple
 
 # Unique missing object.
 _missing = object()
@@ -76,44 +78,44 @@
 QUOTE = b'"'[0]
 
 
-def parse_options_header(value):
+def parse_options_header(value: Union[str, bytes]) -> Tuple[bytes, Dict[bytes, bytes]]:
  """
  Parses a Content-Type header into a value in the following format:
  (content_type, {parameters})
  """
+ # Uses email.message.Message to parse the header as described in PEP 594.
+ # Ref: https://peps.python.org/pep-0594/#cgi
  if not value:
  return (b'', {})
 
- # If we are passed a string, we assume that it conforms to WSGI and does
- # not contain any code point that's not in latin-1.
- if isinstance(value, str): # pragma: no cover
- value = value.encode('latin-1')
+ # If we are passed bytes, we assume that it conforms to WSGI, encoding in latin-1.
+ if isinstance(value, bytes): # pragma: no cover
+ value = value.decode('latin-1')
+
+ # For types
+ assert isinstance(value, str), 'Value should be a string by now'
 
  # If we have no options, return the string as-is.
- if b';' not in value:
- return (value.lower().strip(), {})
+ if ";" not in value:
+ return (value.lower().strip().encode('latin-1'), {})
 
  # Split at the first semicolon, to get our value and then options.
- ctype, rest = value.split(b';', 1)
+ # ctype, rest = value.split(b';', 1)
+ message = Message()
+ message['content-type'] = value
+ params = message.get_params()
+ # If there were no parameters, this would have already returned above
+ assert params, 'At least the content type value should be present'
+ ctype = params.pop(0)[0].encode('latin-1')
  options = {}
-
- # Parse the options.
- for match in OPTION_RE.finditer(rest):
- key = match.group(1).lower()
- value = match.group(2)
- if value[0] == QUOTE and value[-1] == QUOTE:
- # Unquote the value.
- value = value[1:-1]
- value = value.replace(b'\\\\', b'\\').replace(b'\\"', b'"')
-
+ for param in params:
+ key, value = param
  # If the value is a filename, we need to fix a bug on IE6 that sends
  # the full file path instead of the filename.
- if key == b'filename':
- if value[1:3] == b':\\' or value[:2] == b'\\\\':
- value = value.split(b'\\')[-1]
-
- options[key] = value
-
+ if key == 'filename':
+ if value[1:3] == ':\\' or value[:2] == '\\\\':
+ value = value.split('\\')[-1]
+ options[key.encode('latin-1')] = value.encode('latin-1')
  return ctype, options