A code linter

• JavaScript, TypeScript, JSX, TSX

  • no extra dependencies

• Helpful diagnostics

• 200 lint rules

  • some unique to Biome
  • ESLint, ESLint plugins
  • Tailwind class sorting

A code formatter

• JavaScript, TypeScript, JSX, TSX
• JSON, JSONC
• CSS
• format invalid code

A community

• 170k weekly downloads
• 8.4k GitHub Stars
• 4.6k followers
• 1.2k Discord members

Architecture

• leader-follower
• the leader thread
  • spawn a thread per file
  • collect results
• a follower thread
  • parse the given file
  • handle (format, lint)

Regular parser

1. parse to an Abstract Syntax Tree
2. handle (format, lint)

Regular parser

• doesn't handle invalid code
  • emit syntax error

Biome parser

• accept invalid code

  • bogus tree nodes
  • holes in the tree

• lossless parsing using CST

  • preserve whitespace

Biome parser

• accept invalid code

  • bogus tree nodes
  • holes in the tree

• lossless parsing using CST

  • preserve whitespace

Lint rules

• many rules query the tree

  • noVar
  • noDoubleEquals
  • noAccumulatingSpread

• others need more complex data

  • noUnusedVariables
  • noUnusedImports
  • useImportType
  • useExportType

Semantic model

• find references of a declaration
  • write refrences
  • read references

Name resolver v1

• bind declarations to references
  • unique id for each declaration
  • a reference refers to a single declaration
• take scopes into account
  • variable shadowing

TypeScript

• type & variable with same name

TypeScript

• type & variable with same name
• a reference can refer to a type and a variable

TypeScript

• type & variable with same name
• a reference can refer to a type and a variable
• a reference can refer to multiple declarations

TypeScript

• type & variable with same name
• a reference can refer to a type and a variable
• a reference can refer to multiple declarations
• partially referenced declarations
  • type / variable duality

Simplification

• a reference refers to a single declaration
  • handle differently edge cases (export, infer)
• type and variable with same name
• type / variable duality

Name resolver v2

• A declaration is either
  • a type
  • a variable
  • both
• A reference refers either
  • a type
  • a varaible

Name resolver v2

• A declaration is either
  • a type
  • a variable
  • both
• A reference refers either
  • a type
  • a varaible
• type/value duality not exposed

Conclusion

• Biome is both a formatter and a linter
  • and more: JavaScript import sorting
• Biome is fast
• Biome is editor-ready
  • error-resilient parsers
  • Concrete Syntax Tree
• Biome supports TypeScript
  • type-aware semantic model

2024 and beyond

• extend to more languages
  • CSS, HTML, Markdown
  • Vue, Angular, Svelte, Astro
• improve linter capabilities
  • multi-file analysis
  • simplified type system
• plugins

Want to help?

• try Biome
  • report issues
  • feedbacks
• contribute to Biome
  • GitHub good first issues
  • How to create a lint rule in Biome
    (youtube.com/@Biomejs)
• sponsor us!
  • Biome Open Collective

A toolchain

• toolchain for web dev
  • code formatter
  • code linter
• written in Rust
• supports main web language
  • JavaScript, TypeScript, JSX, TSX
  • JSON, JSONC
  • CSS
• community successor of Rome Tools

A fast formatter

• scales with available threads

A governance

• leads (2) owners

  • access to sensible data
  • act as tiebreakers

• core contributors (5)

  • project directions

• maintainers (5)

  • project decisions
  • write access to the repo