Formatter Development

Use crates/biome_formatter/CONTRIBUTING.md and the language formatter's guide as the canonical architecture references. Inspect neighboring node implementations before selecting IR primitives.

Workflow

1. Reproduce the behavior with a focused internal formatter spec or quick_test.
2. Inspect the node fields, comments, and nearby formatting rules.
3. Implement the smallest layout change using formatter IR.
4. Run focused formatter tests and inspect snapshots.
5. Compare with Prettier when compatibility is relevant.
6. Format and lint before committing.

Printing Discipline

Formatter output is a structured rewrite of the source tree, not a fresh pretty-printer. Treat every missed node, missed token, unchecked suppression, and untracked replacement as a formatter bug, not as style feedback.