ESLint

The ESLint module checks JavaScript and TypeScript source with ESLint, running the same lint check locally and in CI so issues get caught before a PR lands. Each ESLint config roots a project, and the module lints each project with its own config.

Add it to your workspace

dagger module install dagger.io/js/eslint

Run the check

dagger check --eslint                          # lint every project
dagger check --eslint-project=packages/ui      # lint one project

The check is eslint/projects/lint. It installs dependencies and runs the project's own ESLint from the project directory, so the result matches what developers see locally. A check over several projects reports every project that fails.

Projects

Flag	Collection	Key
--eslint-project	projects	Directory holding the ESLint config, relative to the workspace root. The root is .

List the keys with dagger list eslint-projects -a. Select collection items describes how to select items.

A project is a directory holding a flat config (eslint.config.js, .mjs, .cjs, .ts, .mts, or .cts) or a legacy config (.eslintrc, .eslintrc.js, .cjs, .json, .yaml, or .yml). A nested project is linted on its own, and the project that encloses it skips its files. A config in a directory that the enclosing flat config ignores globally is not a project.

Projects are found at or below the directory dagger runs from, plus the nearest project that encloses it.

Dependencies install at the nearest workspace root (a pnpm-workspace.yaml or a package.json with workspaces), else the nearest lockfile, else the nearest package.json.

Fix issues

Each project has a fix function that runs eslint --fix and returns the repaired source as a changeset. Problems ESLint cannot fix are left for the check to report. It is a regular function rather than a check, so it does not run during dagger check:

dagger -c 'eslint | projects | get packages/ui | fix | export .'

Configure it

List the current settings and their values with dagger module settings eslint, then set one with dagger module settings eslint <key> <value>. Settings are stored in dagger.toml under [modules.eslint.settings] and apply to every project:

• packageManager (default empty) is the package manager that installs dependencies: npm, pnpm, yarn, or bun. Empty detects it from the packageManager field of package.json, then from the lockfile, then uses npm.
• baseImageAddress (default node:25-alpine) is the Node base image ESLint runs in. Pin it to the project's Node version, for example node:22-alpine.
• installFlags (default empty) are extra arguments for the install command, such as ["--ignore-scripts"].
• environment (default empty) sets environment variables for ESLint, as KEY=VALUE.

[modules.eslint.settings]
baseImageAddress = "node:22-alpine"
installFlags = ["--ignore-scripts"]

Working with other modules

Use ESLint with Prettier when the project separates lint rules from formatting. Use Biome when the project has moved linting and formatting into one tool.

source code