Biome v1.7

Victorien Elvinger & Biome Core Team, Biome Maintainers

April 15, 2024

Today we’re excited to announce the release of Biome v1.7!

This new version provides an easy path to migrate from ESLint and Prettier. It also introduces experimental machine-readable reports for the formatter and the linter, new linter rules, and many fixes.

Update Biome using the following commands:

npm install --save-dev --save-exact @biomejs/biome@latest
npx @biomejs/biome migrate

Migrate from ESLint with a single command

This release introduces a new subcommand biome migrate eslint. This command will read your ESLint configuration and attempt to port their settings to Biome.

The subcommand is able to handle both the legacy and the flat configuration files. It supports the extends field of the legacy configuration and loads both shared and plugin configurations! The subcommand also migrates .eslintignore.

Given the following ESLint configuration:

{
  "extends": ["plugin:unicorn/recommended"],
  "plugins": ["unicorn"],
  "ignore_patterns": ["dist/**"],
  "globals": {
    "Global1": "readonly"
  },
  "rules": {
    "eqeqeq": "error"
  },
  "overrides": [
    {
      "files": ["tests/**"],
      "rules": {
        "eqeqeq": "off"
      }
    }
  ]
}

And the following Biome configuration:

{
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true
    }
  }
}

Run biome migrate eslint --write to migrate your ESLint configuration to Biome. The command overwrites your initial Biome configuration. For example, it disables recommended. This results in the following Biome configuration:

{
  "organizeImports": { "enabled": true },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": false,
      "complexity": {
        "noForEach": "error",
        "noStaticOnlyClass": "error",
        "noUselessSwitchCase": "error",
        "useFlatMap": "error"
      },
      "style": {
        "noNegationElse": "off",
        "useForOf": "error",
        "useNodejsImportProtocol": "error",
        "useNumberNamespace": "error"
      },
      "suspicious": {
        "noDoubleEquals": "error",
        "noThenProperty": "error",
        "useIsArray": "error"
      }
    }
  },
  "javascript": { "globals": ["Global1"] },
  "overrides": [
    {
      "include": ["tests/**"],
      "linter": { "rules": { "suspicious": { "noDoubleEquals": "off" } } }
    }
  ]
}

The subcommand needs Node.js to load and resolve all the plugins and extends configured in the ESLint configuration file. For now, biome migrate eslint doesn’t support configuration written in YAML.

We have a dedicated page that lists the equivalent Biome rule of a given ESLint rule. We handle some ESLint plugins such as TypeScript ESLint, ESLint JSX A11y, ESLint React, and ESLint Unicorn. Some rules are equivalent to their ESLint counterparts, while others are inspired. By default, Biome doesn’t migrate inspired rules. You can use the CLI flag --include-inspired to migrate them.

Migrate from Prettier with a single command

Biome v1.6 introduced the subcommand biome migrate prettier.

In Biome v1.7, we add support of Prettier’s overrides and attempts to convert .prettierignore glob patterns to globs supported by Biome.

During the migration, Prettier’s overrides is translated to Biome’s overrides. Given the following .prettierrc.json

{
  "useTabs": false,
  "singleQuote": true,
  "overrides": [
    {
          "files": ["*.json"],
          "options": { "tabWidth": 2 }
      }
  ]
}

Run biome migrate prettier --write to migrate your Prettier configuration to Biome. This results in the following Biome configuration:

{
  "formatter": {
    "enabled": true,
    "formatWithErrors": false,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineEnding": "lf",
    "lineWidth": 80,
    "attributePosition": "auto"
  },
  "organizeImports": { "enabled": true },
  "linter": { "enabled": true, "rules": { "recommended": true } },
  "javascript": {
    "formatter": {
      "jsxQuoteStyle": "double",
      "quoteProperties": "asNeeded",
      "trailingComma": "all",
      "semicolons": "asNeeded",
      "arrowParentheses": "always",
      "bracketSpacing": true,
      "bracketSameLine": false,
      "quoteStyle": "single",
      "attributePosition": "auto"
    }
  },
  "overrides": [
    {
      "include": ["*.json"],
      "formatter": {
        "indentWidth": 2
      }
    }
  ]
}

The subcommand needs Node.js to load JavaScript configurations such as .prettierrc.js. biome migrate prettier doesn’t support configuration written in JSON5, TOML, or YAML.

Emit machine-readable reports

Biome is now able to output JSON reports detailing the diagnostics emitted by a command.

For instance, you can emit a report when you lint a codebase:

biome lint --reporter=json-pretty .

For now, we support two report formats: json and json-pretty.

Note that the report format is experimental, and it might change in the future. Please try this feature and let us know if any information needs to be added to the reports.

Check `git` staged files

Biome v1.5 added the --changed to format and lint git tracked files that have been changed.

Today we are introducing a new option --staged which allows you to check only files added to the Git index (staged files). This is useful for checking that the files you want to commit are formatted and linted:

biome check --staged .

This is handy for writing your own pre-commit script. Note that unstaged changes on a staged file are not ignored. Thus, we still recommend using a dedicated pre-commit tool.

Thanks to @castarco for implementing this feature!

Linter

New nursery rules

Since Biome v1.6, we added several new rules. New rules are incubated in the nursery group. Nursery rules are exempt from semantic versioning.

The new rules are:

Promoted rules

Once stable, a nursery rule is promoted to a stable group. The following rules are promoted:

Miscellaneous

By default, Biome searches a configuration file in the working directory and parent directories if it doesn’t exist. Biome provides a CLI option --config-path and an environment variable BIOME_CONFIG_PATH that allows which can be used to override this behavior. Previously, they required a directory containing a Biome configuration file. For example, the following command uses the Biome configuration file in ./config/.
Terminal window
```
biome format --config-path=./config/ ./src
```
This wasn’t very clear for many users who are used to specifying the configuration file path directly. They now accept a file, so the following command is valid:
Terminal window
```
biome format --config-path=./config/biome.json ./src
```
You can now ignore React imports in the rules noUnusedImports and useImportType by setting javascript.jsxRuntime to reactClassic.
Biome applies specific settings to well-known files. It now recognizes more files and distinguishes between JSON files that only allow comments and JSON files that allow both comments and trailing commas.
In the React ecosystem, files ending in .js are allowed to contain JSX syntax. The Biome extension is now able to parse JSX syntax in files that are associated with the JavaScript language identifier.
useExhaustiveDependencies now supports Preact.

See the changelog for more details.

What’s Next?

We have started work on the CSS formatter and linter. Early implementation towards a plugin system is also underway. Some of our contributors have started preliminary work for GraphQL and YAML. Any help is welcome!

If Biome is valuable to you or your company, consider donating monthly to our Open Collective. You can also sponsor us on GitHub. This is important for the sustainability of the project.