diagnostics-development

Purpose

Use this skill when creating diagnostics - the error messages, warnings, and hints shown to users. Covers the Diagnostic trait, advice types, and best practices for clear, actionable messages.

Prerequisites

1. Read crates/biome_diagnostics/CONTRIBUTING.md for concepts
2. Understand Biome's Technical Principles
3. Follow the "show don't tell" philosophy

Diagnostic Principles

1. Explain what - State what the error is (diagnostic message)
2. Explain why - Explain why it's an error (advice notes)
3. Tell how to fix - Provide actionable fixes (code actions, diff advice, command advice)