Bug 2079840 - allow @username in the textarea like github

[dklawren]

Bug 2079840 - Support GitHub-style @Nickname mentions to needinfo and CC users

Summary

When a user with editbugs adds a comment to an existing bug that contains @nickname, each mentioned user is CC'd and gets a needinfo request. Several mentions in one comment (@alice, @bob) each get a needinfo. Safeguards limit who can trigger mentions, how many are processed, and make sure a mention never grants access to a restricted bug.

Behavior

• Matching: a mention matches the profile nickname field of an enabled account. If a nickname matches several accounts, or none, it is skipped silently. It is never guessed.
• Ignored: email addresses ([email protected]), quoted lines (> ...), inline code (any number of backticks), fenced code blocks, and mentioning yourself.
• Needinfo vs CC: mentioned users are always CC'd. The needinfo is skipped if the user blocks needinfo or already has a needinfo pending. If a site's needinfo type is not multiplicable, at most one needinfo is requested.
• Never blocks saving: each mentioned user is processed in an eval under ERROR_MODE_DIE. A failure, such as add_cc's strict_isolation check, skips that user and logs a WARN instead of rolling back the comment.
• Private comments: a mention that appears only in private comments counts only if that user is an insider.
• Scope: only comments added to existing bugs. The description of a new bug is not parsed.
• Mass edit: mentions are processed on every bug in a mass edit.

Safeguards

• Only editbugs users trigger mentions (product-specific, the same check core uses). For everyone else, @nickname is plain text, so there is no lookup, CC or needinfo.
• At most 10 mentions per update: only the first 10 distinct nicknames are processed (MAX_MENTIONS), and the rest are ignored. This prevents notification spam from one comment.
• No access by mention: mentioned users who cannot already see the bug are skipped entirely, with no CC and no needinfo. A typo, or a nickname someone else has claimed (squatting), can never expose a security bug.

Implementation

• extensions/Needinfo/Extension.pm
  • The needinfo flag type is now created with is_multiplicable => 1, matching production. This only affects new installs.
  • bug_start_of_update now calls the existing form handling (moved unchanged into _process_needinfo_params), then _process_mentions. Mentions run second, so a needinfo just requested through the form is detected and not duplicated.
  • _extract_mentions parses the comment text. It is a pure function covered by unit tests.
  • _users_for_mentions resolves nicknames with one query and drops nicknames shared by more than one account.
  • _process_mentions applies the safeguards. Updates with no mentions return before any database work.
  • _cc_and_needinfo adds the CC and needinfo for one user.
• extensions/Needinfo/t/mentions.t
  • Parser tests.
  • Behavior tests for CC plus needinfo, skipping yourself, skipping users who can't see the bug, the cap of 10, the editbugs gate, non-multiplicable types, no duplicate needinfo, and a failing CC not throwing.

Known limitations

• Mentions are parsed with regexes, not the Markdown renderer, so indented code blocks and HTML <code> are not ignored.
• _users_for_mentions (one SQL query) has no unit test.
• Unknown or ambiguous nicknames count toward the cap of 10.

Testing

• test_sanity: extensions/Needinfo/t/mentions.t, t/001compile.t, t/002goodperl.t, t/005whitespace.t, t/critic.t all pass.
• Not yet covered: webservices or Selenium tests, and a manual check in the dev stack.

[Copilot]

🟡 Changes recommended

Multiple valid scenarios can incorrectly trigger mentions or roll back comment submission.

7 open findings

• Allow multiple Needinfo flags for multiple mentions · New
• Remove multi-backtick inline code spans from mention parsing · New
• Support pipe characters in extracted mention nicknames · New
• Prevent ineligible mention users from rolling back comment updates · New
• Implement claimed @​nickname mention behavior or correct PR scope
• Add stateful tests for mention processing and failure handling · New
• Remove redundant animation wait and duplicate timeout diagnostics

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Longer fenced code blocks can close early, causing mentions inside code to be processed.

1 open finding

• Capture full fence length to prevent premature code block closure · New

7 resolved since last review

• Allow multiple Needinfo flags for multiple mentions
• Prevent ineligible mention users from rolling back comment updates
• Support pipe characters in extracted mention nicknames
• Remove multi-backtick inline code spans from mention parsing
• Implement claimed @​nickname mention behavior or correct PR scope
• Add stateful tests for mention processing and failure handling
• Remove redundant animation wait and duplicate timeout diagnostics

🧠 Review effort: Balanced