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Configure Linters

This guide shows how to set up common linters and formatters in datamitsu's tooling system.

Setting Up golangci-lint​

golangci-lint is a Go linter aggregator. Since it operates on Go modules rather than individual files, configure it with scope: "repository".

1. Ensure the app is defined​

The default configuration includes golangci-lint as a binary app. If you need a custom version, override it in your config:

/// <reference path=".datamitsu/datamitsu.config.d.ts" />

function getConfig(config) {
  return {
    ...config,
    apps: {
      ...config.apps,
      "golangci-lint": {
        binary: {
          binaries: {
            // platform-specific URLs and hashes
          },
        },
      },
    },
  };
}
globalThis.getConfig = getConfig;

2. Define the tool​

const tools = {
  ...config.tools,
  "golangci-lint": {
    name: "golangci-lint",
    projectTypes: ["golang-package"],
    operations: {
      lint: {
        app: "golangci-lint",
        args: ["run", "--timeout", "5m"],
        scope: "repository",
        globs: ["**/*.go"],
        env: {
          GOLANGCI_LINT_CACHE: "{toolCache}",
        },
      },
    },
  },
};

Key points:

  • scope: "repository" runs it once from the git root, not per-project
  • {toolCache} gives golangci-lint an isolated cache directory
  • Only a lint operation is defined since golangci-lint doesn't auto-fix

Setting Up ESLint via FNM​

ESLint is a JavaScript/TypeScript linter managed through the FNM runtime.

1. Define the app​

apps: {
  ...config.apps,
  eslint: {
    fnm: {
      packageName: "eslint",
      version: "9.0.0",
      binPath: "node_modules/.bin/eslint",
      lockFile: "br:...",  // generated via: datamitsu config lockfile eslint
    },
    links: {
      "eslint-config": "dist/eslint.config.js",
    },
  },
}

2. Define the tool​

const tools = {
  ...config.tools,
  eslint: {
    name: "ESLint",
    projectTypes: ["npm-package"],
    operations: {
      fix: {
        app: "eslint",
        args: ["--fix", "{files}"],
        scope: "per-project",
        globs: ["**/*.{js,ts,jsx,tsx}"],
      },
      lint: {
        app: "eslint",
        args: ["{files}"],
        scope: "per-project",
        globs: ["**/*.{js,ts,jsx,tsx}"],
      },
    },
  },
};

In your project's ESLint config, use tools.Config.linkPath() to reference the managed configuration:

// In a ConfigInit content function
const eslintConfigPath = tools.Path.forImport(
  tools.Config.linkPath("eslint", "eslint-config", context.cwdPath),
);

Setting Up Ruff via UV​

Ruff is a fast Python linter and formatter managed through the UV runtime.

1. Define the app​

apps: {
  ...config.apps,
  ruff: {
    uv: {
      packageName: "ruff",
      version: "0.3.0",
      lockFile: "br:...",  // generated via: datamitsu config lockfile ruff
    },
  },
}

2. Define the tool​

const tools = {
  ...config.tools,
  ruff: {
    name: "Ruff",
    projectTypes: ["python"],
    operations: {
      fix: {
        app: "ruff",
        args: ["format", "{files}"],
        scope: "per-project",
        globs: ["**/*.py"],
      },
      lint: {
        app: "ruff",
        args: ["check", "{files}"],
        scope: "per-project",
        globs: ["**/*.py"],
      },
    },
  },
};

Configuring Ignore Rules​

Use ignore rules to skip tools for specific files or directories.

Using .datamitsuignore files​

Create a .datamitsuignore file in any directory:

# Disable all tools for vendor code
vendor/**/*: *

# Disable prettier for auto-generated files
**/*.generated.ts: prettier

# Disable eslint for test fixtures
tests/fixtures/**/*: eslint, prettier

Using config-defined ignore rules​

Add ignore rules directly in your configuration:

/// <reference path=".datamitsu/datamitsu.config.d.ts" />

function getConfig(config) {
  return {
    ...config,
    ignoreRules: [
      "vendor/**/*: *",
      "**/*.generated.go: golangci-lint, gofmt",
      "!vendor/patches/**/*: *", // re-enable for patches
    ],
  };
}
globalThis.getConfig = getConfig;

Re-enabling tools​

Use the ! prefix to re-enable tools disabled by broader rules:

# Disable eslint for all markdown
**/*.md: eslint

# But re-enable for documentation
!docs/**/*.md: eslint

See the Ignore Rules reference for full syntax details.

Previewing Tool Execution​

Before running tools, use --explain to see what would execute:

# Summary of planned tasks
datamitsu check --explain

# Detailed breakdown
datamitsu check --explain detailed

# Machine-readable output
datamitsu check --explain json

Running Specific Tools​

Use --tools to run only certain tools:

# Run only ESLint and Prettier
datamitsu check --tools eslint,prettier

# Fix only with Ruff
datamitsu fix --tools ruff

Git Hook Integration​

Use --file-scoped to check only staged files in a pre-commit hook:

datamitsu check --file-scoped

This pairs well with tools like lefthook for git hook management.