file-good-first-bug

What is a good first bug

A bug a newcomer can pick up cold and finish in one short patch. The hallmarks:

• Narrow scope - one file or one tiny area. Multiple newcomers can work in parallel without conflict.
• Self-contained - the bug body contains everything: what to change, where to find it, how to reproduce / verify, and links to the contribution quickref. The contributor should not need to ask follow-up questions.
• Low risk - fix is mechanical or obvious. No design decisions, no API redesign, no cross-module reasoning.
• Verifiable - there's a clear signal the patch is correct (a lint that stops firing, a test that passes, a doc that renders, a warning that disappears).

Linter output is just one source of such tasks. Other good sources:

• A small typo or wording fix in code/docs the user spotted
• Removing one piece of dead code the user identified
• Converting one RST doc page to Markdown (or similar mechanical migration)
• Replacing one deprecated API call with its successor in a single file
• Adding a missing test for one small behavior
• Renaming one symbol consistently within a contained module

If the task touches many files, requires API design, or needs deep domain knowledge - it's not a good first bug. Push back on the user before filing.

Workflow

1. Understand the task source. The user will point at something: a file, a lint output, a typo, a paragraph of docs, a deprecated call site. Read enough to confirm the work is genuinely narrow.

2. Decide on bug shape. Prefer one bug per file / per atomic task. Combine only if the user explicitly asks. Multiple small bugs let newcomers work in parallel and is the established Firefox precedent (e.g. bug 2031381).

3. Propose to the user before filing. Use AskUserQuestion to confirm scope and which items to file. Never generate bug URLs without explicit approval - filing bugs is user-visible.

4. Generate prefilled enter_bug.cgi URLs. There is no MCP tool to create Bugzilla bugs - the user submits each bug by clicking its URL. Use the URL builder below.

5. Print the URLs, one per item, prefixed with what the bug is about so the user can scan and click.

Choosing product/component

Most Firefox good-first-bugs go to Developer Infrastructure / Lint and Formatting when they come from lint output, since that's the team that owns the trackers. For other sources, route to the component that owns the affected code:

• Docs conversions → the component of the docs (often Developer Infrastructure / Source Documentation)
• Code typos / dead-code → the component that owns the file
• API call-site updates → the component using the API

Ask the user if you're unsure - don't guess.

Tracker bug

Good-first-bugs typically blocks: a tracker bug so the metawork is visible. Known trackers:

• clippy warnings → 1361342
• ruff warnings → 1968295
• Coverity issues → 1230156
• clang-based static analysis → 712350
• other linters → ask the user

For non-lint bugs there may or may not be a tracker. Ask the user; if there isn't one, omit blocked.

Whiteboard

Set the Bugzilla whiteboard (status_whiteboard) to [lang=LANGUAGE] so newcomers can filter good-first-bugs by language. Use the full language name:

• Rust → [lang=rust]
• Python → [lang=python]
• JavaScript → [lang=js]
• C++ → [lang=c++]
• HTML / CSS → [lang=html] / [lang=css]
• Markdown / docs → [lang=md]

Pick the language of the file the contributor will actually edit. If a bug spans languages, list both: [lang=rust][lang=python].

Mentor

Always set a mentor (bug_mentors) on the bug, defaulting to the bug filer. Without a mentor the bug won't show up in some good-first-bug dashboards, and a newcomer's comments or questions may be lost because nobody is clearly responsible for answering them.

The filer is the person running this skill - use their Bugzilla email (the email of the user submitting the bug). If you don't know it, ask the user. Pass it to the URL builder with --mentor.

Comment body template

The body must be self-sufficient. Adapt this skeleton:

Filing as a good first bug to learn workflows.

<one short paragraph: what to do and where>

<optional: warning list / code snippet / current vs. desired>

Link to the code:
https://searchfox.org/mozilla-central/source/<path>[#<line>]

To verify the fix:

<the exact command(s) the contributor should run, e.g.>
./mach lint -W -l clippy <path>
./mach test <path>
./mach doc --no-serve --no-open

<optional: brief note about why the change is desired>

Tutorial to contribute:
https://firefox-source-docs.mozilla.org/contributing/contribution_quickref.html
https://firefox-source-docs.mozilla.org/contributing/stack_quickref.html

Please don't ask for the bug to be assigned. It will be automatically assigned to the first patch.

The last paragraph (about auto-assignment) is canonical - keep it verbatim.

URL builder

Use the helper script scripts/build_url.py (path relative to this skill file) to generate each prefilled enter_bug.cgi URL:

./scripts/build_url.py "<title>" "<comment>" --tracker 1361342 --lang rust --mentor you@mozilla.com

Run it with --help for the full list of options (--product, --component, --tracker, --keywords, --lang, --mentor). It can also be imported and its build_url() function called directly. Always pass --mentor with the filer's email (see Mentor).

Example: lint warnings (canonical case)

This is the pattern bug 2031381 established. For each candidate file with 1-3 trivial warnings:

• Title: Fix clippy warnings in <path>
• Body lists the warnings, links searchfox at the first warning line, gives the ./mach lint -W -l clippy <path> reproducer.
• Product/Component: Developer Infrastructure / Lint and Formatting
• Blocks: 1361342

Avoid these lints in good-first-bugs unless the user explicitly accepts the extra scope:

• clippy::too_many_arguments - needs API refactoring
• clippy::missing_safety_doc - needs writing real Safety docs
• clippy::type_complexity - needs designing a type alias

Quick grouping of warnings by file:

awk '/^\// { f=$0; next } /warning/ { c[f]++; lines[f]=lines[f] "\n" $0 }
     END { for (f in c) if (c[f] <= 3) print c[f]"\t"f lines[f] }' clippy.txt | sort -n

Example: typo fix

• Title: Fix typo "recieve" in <path>
• Body: quote the offending line(s), point at searchfox, give the corrected wording.
• Component: whatever owns <path>.
• No tracker unless the user names one.

Example: docs conversion

• Title: Convert <path> from RST to Markdown
• Body: link to the existing RST file, explain the target is .md with the same content, point to a recent landed conversion as a reference, give ./mach doc --no-serve --no-open as the verification command.
• Component: Developer Infrastructure / Source Documentation.

Reminders

• One bug per atomic task unless the user opts into a combined bug.
• Always set a mentor (--mentor), defaulting to the bug filer - otherwise the bug is invisible in some dashboards and questions go unanswered.
• Don't auto-assign - the template explicitly tells contributors not to ask.
• Push back on scope that's too big, too vague, or requires design decisions - those are not good-first-bugs.
• Match the component to the work - don't dump everything under Lint and Formatting if the bug isn't a lint bug.