fix: accept a negative Set-Cookie Max-Age attribute

[arshsmith1]

This relates to...

N/A

Rationale

parseUnparsedAttributes in lib/web/cookies/parse.js validates the Max-Age attribute-value with /^\d+$/, applied to the whole value rather than to the remainder after the sign. Any negative Max-Age therefore fails the check and the attribute is dropped from the parsed cookie:

getSetCookies(new Headers({ 'set-cookie': 'id=a; Max-Age=-1' }))
// [{ name: 'id', value: 'a' }]
// should be: [{ name: 'id', value: 'a', maxAge: -1 }]

RFC 6265bis section 5.6.2 is explicit that a leading - is allowed:

If the first character of the attribute-value is neither a DIGIT, nor a "-" character followed by a DIGIT, ignore the cookie-av.

If the remainder of attribute-value contains a non-DIGIT character, ignore the cookie-av.

If delta-seconds is less than or equal to zero (0), let expiry-time be the earliest representable date and time.

The step-1 check at line 193 already accepts - as a first character, and the last step above only has meaning if negative values reach it, so the intent in the surrounding code is the spec behaviour. Max-Age=-1 is the usual way a server expires a cookie, and today that signal is silently lost by getSetCookies().

The generation side is deliberately left alone: validateCookieMaxAge still rejects negatives, which matches the max-age-av = "Max-Age=" non-zero-digit *DIGIT grammar a server must emit. Parsing is permissive, serialising stays strict.

Changes

Relax the digit check to /^-?\d+$/ so a single leading sign is accepted and a non-DIGIT remainder is still ignored. Max-Age=-, --1, -1a, +1 and the empty value all stay ignored, and positive values are unchanged.

Features

N/A

Bug Fixes

• Set-Cookie: ...; Max-Age=-1 now parses to maxAge: -1 instead of dropping the attribute.

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Documented
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.48%. Comparing base (1383989) to head (317fc61).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5571      +/-   ##
==========================================
+ Coverage   93.47%   93.48%   +0.01%     
==========================================
  Files         110      110              
  Lines       37560    37560              
==========================================
+ Hits        35108    35112       +4     
+ Misses       2452     2448       -4     

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