Create Plugins

An ESLint plugin is an extension for ESLint that adds additional rules and configuration options. Plugins let you customize your ESLint configuration to enforce rules that are not included in the core ESLint package. Plugins can also provide additional environments, custom processors, and configurations.

Name a Plugin

Each plugin is an npm module with a name in the format of eslint-plugin-<plugin-name>, such as eslint-plugin-jquery. You can also use scoped packages in the format of @<scope>/eslint-plugin-<plugin-name> such as @jquery/eslint-plugin-jquery or even @<scope>/eslint-plugin such as @jquery/eslint-plugin.

Create a Plugin

The easiest way to start creating a plugin is to use the Yeoman generator. The generator will guide you through setting up the skeleton of a plugin.

Rules in Plugins

Plugins can expose custom rules for use in ESLint. To do so, the plugin must export a rules object containing a key-value mapping of rule ID to rule. The rule ID does not have to follow any naming convention (so it can just be dollar-sign, for instance). To learn more about creating custom rules in plugins, refer to Custom Rules.

module.exports = {
    rules: {
        "dollar-sign": {
            create: function (context) {
                // rule implementation ...
            }
        }
    }
};
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To use the rule in ESLint, you would use the unprefixed plugin name, followed by a slash, followed by the rule name. So if this plugin were named eslint-plugin-myplugin, then in your configuration you’d refer to the rule by the name myplugin/dollar-sign. Example: "rules": {"myplugin/dollar-sign": 2}.

Environments in Plugins

Plugins can expose additional environments for use in ESLint. To do so, the plugin must export an environments object. The keys of the environments object are the names of the different environments provided and the values are the environment settings. For example:

module.exports = {
    environments: {
        jquery: {
            globals: {
                $: false
            }
        }
    }
};
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There’s a jquery environment defined in this plugin. To use the environment in ESLint, you would use the unprefixed plugin name, followed by a slash, followed by the environment name. So if this plugin were named eslint-plugin-myplugin, then you would set the environment in your configuration to be "myplugin/jquery".

Plugin environments can define the following objects:

globals - acts the same globals in a configuration file. The keys are the names of the globals and the values are true to allow the global to be overwritten and false to disallow.
parserOptions - acts the same as parserOptions in a configuration file.

Processors in Plugins

You can add processors to plugins by including the processor functions in the processors key. For more information on defining custom processors, refer to Custom Processors.

module.exports = {
    processors: {
        // This processor will be applied to `*.md` files automatically.
        ".md": {
            preprocess(text, filename) { /* ... */ },
            postprocess(messages, filename) { /* ... */ }
        }
        "processor-name": {
            preprocess: function(text, filename) {/* ... */},

            postprocess: function(messages, filename) { /* ... */ },
        }
    }
}
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Configs in Plugins

You can bundle configurations inside a plugin by specifying them under the configs key. This can be useful when you want to bundle a set of custom rules with additional configuration. Multiple configurations are supported per plugin.

You can include individual rules from a plugin in a config that’s also included in the plugin. In the config, you must specify your plugin name in the plugins array as well as any rules you want to enable that are part of the plugin. Any plugin rules must be prefixed with the short or long plugin name.

// eslint-plugin-myPlugin

module.exports = {
    configs: {
        myConfig: {
            plugins: ["myPlugin"],
            env: ["browser"],
            rules: {
                semi: "error",
                "myPlugin/my-rule": "error",
                "eslint-plugin-myPlugin/another-rule": "error"
            }
        },
        myOtherConfig: {
            plugins: ["myPlugin"],
            env: ["node"],
            rules: {
                "myPlugin/my-rule": "off",
                "eslint-plugin-myPlugin/another-rule": "off",
                "eslint-plugin-myPlugin/yet-another-rule": "error"
            }
        }
    },
    rules: {
        "my-rule": {/* rule definition */},
        "another-rule": {/* rule definition */},
        "yet-another-rule": {/* rule definition */}
    }
};
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Plugins cannot force a specific configuration to be used. Users must manually include a plugin’s configurations in their configuration file.

If the example plugin above were called eslint-plugin-myPlugin, the myConfig and myOtherConfig configurations would then be usable in a configuration file by extending "plugin:myPlugin/myConfig" and "plugin:myPlugin/myOtherConfig", respectively.

// .eslintrc.json

{
    "extends": ["plugin:myPlugin/myConfig"]
}

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Meta Data in Plugins

For easier debugging and more effective caching of plugins, it’s recommended to provide a name and version in a meta object at the root of your plugin, like this:

// preferred location of name and version
module.exports = {
    meta: {
        name: "eslint-plugin-custom",
        version: "1.2.3"
    }
};
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The meta.name property should match the npm package name for your plugin and the meta.version property should match the npm package version for your plugin. The easiest way to accomplish this is by reading this information from your package.json.

As an alternative, you can also expose name and version properties at the root of your plugin, such as:

// alternate location of name and version
module.exports = {
    name: "eslint-plugin-custom",
    version: "1.2.3"
};
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While the meta object is the preferred way to provide the plugin name and version, this format is also acceptable and is provided for backward compatibility.

Peer Dependency

To make clear that the plugin requires ESLint to work correctly, you must declare ESLint as a peer dependency by mentioning it in the peerDependencies field of your plugin’s package.json.

Plugin support was introduced in ESLint version 0.8.0. Ensure the peerDependencies points to ESLint 0.8.0 or later.

{
    "peerDependencies": {
        "eslint": ">=0.8.0"
    }
}
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Testing

ESLint provides the RuleTester utility to make it easy to test the rules of your plugin.

Linting

ESLint plugins should be linted too! It’s suggested to lint your plugin with the recommended configurations of:

In order to make your plugin available to the community you have to publish it on npm.

To make it easy for others to find your plugin, add these keywords to your package.json file:

eslint
eslintplugin

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