biome

Step-by-step guide for creating and implementing lint rules in Biome's analyzer. Use when implementing rules like noVar, useConst, or any custom lint/assist rule, adding code actions to fix diagnostics, implementing semantic analysis for binding references, or adding configurable options to rules.

Guide for implementing formatting rules using Biome's IR-based formatter infrastructure. Use when implementing formatting for new syntax nodes, handling comments in formatted output, writing or debugging formatter snapshot tests, diagnosing idempotency failures, or comparing Biome's formatting against Prettier for JavaScript, CSS, JSON, HTML, Markdown, or other languages.

Guide for implementing ESLint-to-Biome rule option migrators inside `biome migrate eslint`. Use whenever you add or update a Biome lint rule that has an ESLint source rule with configurable options, need to deserialize plugin-specific ESLint options, or need custom migration logic beyond the auto-generated severity mapping.

Guide for creating high-quality, user-friendly diagnostics in Biome. Use when creating diagnostics for lint rules, adding helpful advice to error messages, implementing code frame displays, or improving diagnostic quality.

Guide for testing workflows and code generation commands in Biome. Use when running snapshot tests for lint rules, managing insta snapshots, or regenerating analyzer/parser/formatter code after changes.