ParseError due to unsupported flag

[awein]

Emails that use a flag value without a leading \ or $ will cause an internal error:
ParseError: unexpected data_item found while looking for flag|right_parenthesis

Example: FLAGS (\Seen JUNK $Junk)

[tonioo]

@awein Which version of the webmail do you use?

[awein]

@tonioo Sorry for not mentioning the versions:
Modoboa: 1.10.5
Webmail: 1.4.3

[tonioo]

That's strange, the regex cleary allows this kind of token: https://github.com/modoboa/modoboa-webmail/blob/master/modoboa_webmail/lib/fetch_parser.py#L93

[awein]

Sure - but JUNK will be treated as data_item type since it's matching that RE first. I had a quick look too but don't think there is an easy fix without reworking the Lexer class.

This snippet should be enough to reproduce the issue:

FetchResponseParser().parse_chunk('1 (UID 1303 FLAGS (\Seen NOTJUNK $NotJunk) RFC822.SIZE 5710 BODYSTRUCTURE ("text" "plain" ("charset" "ISO-8859-15") NIL NIL "quoted-printable" 2634 56 NIL NIL NIL NIL) BODY[HEADER.FIELDS (DATE FROM TO CC SUBJECT)] {154}')

[tonioo]

Indeed, there is a lexer rule conflict and the fix is more complicated than expected...