Eslint

Rationale

We use Eslint as the main static linter for TypeScript source code. Eslint:

Is an old-school TypeScript linter, which means it has many rules implemented and has been thoroughly tested
Is open source
Has a huge number of typing checks
Supports caching already-reviewed files for performance
Provides a language server out of the box, considerably affecting development experience
Integrates in-editor typing using its VS Code extension for development experience
As it is built in JavaScript, it has serious performance limitations

Below are alternatives we are currently considering as possible replacements to Eslint.

Biome is a static linter and formatter, meaning that it no only replaces Eslint but also formatting tools like Prettier
Is open source
Does not have as many typing checks as Eslint but is getting there very fast
Although it currently does not support caching, it is still much faster compared to Eslint
Provides a language server out of the box, considerably improving development experience
Integrates in-editor typing using its VS Code extension for development experience
As it is built in Rust, it is considerably faster compared to other linters and formatters, up to a point where performance is no longer a concern

Biome was last reviewed on Aug 5, 2025.

Oxc is a static linter, it does not support formatting yet
Is open source
Does not have as many typing checks as Eslint but is getting there very fast
Although it currently does not support caching, it is still much faster compared to Eslint
Provides a language server out of the box, considerably improving development experience
Integrates in-editor typing using its VS Code extension for development experience
As it is built in Rust, it is considerably faster compared to other linters and formatters, up to a point where performance is no longer a concern

Oxc was last reviewed on Aug 5, 2025.

We use Eslint to enforce strict code quality on all of Fluid Attacks' TypeScript source code.