eslint-plugin-svelte3

eslint-plugin-svelte3

An ESLint plugin for Svelte v3 components.

Features

• Svelte compiler errors and warnings are exposed as ESLint messages
• Variable references in your template or in store auto-subscriptions are handled when linting for unused variables
• Self-assignments are always allowed, as this is an official pattern for manually triggering reactive updates
• Unused labels called $ are always allowed, as this is the syntax for reactive assignments
• Linting of template expressions in addition to the script blocks

Requirements

• Svelte 3.2+
• ESLint 6+

Installation

Install the plugin package:

npm install eslint-plugin-svelte3

Then add svelte3 to the plugins array in your .eslintrc.*, and set svelte3/svelte3 as the processor for your Svelte components.

For example:

module.exports = {
  parserOptions: {
    ecmaVersion: 2019,
    sourceType: 'module'
  },
  env: {
    es6: true,
    browser: true
  },
  plugins: [
    'svelte3'
  ],
  overrides: [
    {
      files: '*.svelte',
      processor: 'svelte3/svelte3'
    }
  ],
  rules: {
    // ...
  },
  settings: {
    // ...
  }
};

This plugin needs to be able to require('svelte/compiler'). If ESLint, this plugin, and Svelte are all installed locally in your project, this should not be a problem.

Interactions with other plugins

Care needs to be taken when using this plugin alongside others. Take a look at this list of things you need to watch out for.

Configuration

There are a few settings you can use to adjust this plugin's behavior. These go in the settings object in your ESLint configuration.

Passing a function as a value for a setting (which some of the settings below require) is only possible when using a CommonJS .eslintrc.js file, and not a JSON or YAML configuration file.

svelte3/ignore-warnings

This can be a function that indicates whether to ignore a warning in the linting. The function will be passed a warning object and should return a boolean.

The default is to not ignore any warnings.

svelte3/compiler-options

Most compiler options do not affect the validity of compiled components, but a couple of them can. If you are compiling to custom elements, or for some other reason need to control how the plugin compiles the components it's linting, you can use this setting.

This can be an object of compiler options.

The default is to compile with { generate: false }.

svelte3/ignore-styles

If you're using some sort of preprocessor on the component styles, then it's likely that when this plugin calls the Svelte compiler on your component, it will throw an exception. In a perfect world, this plugin would be able to apply the preprocessor to the component and then use source maps to translate any warnings back to the original source. In the current reality, however, you can instead simply disregard styles written in anything other than standard CSS. You won't get warnings about the styles from the linter, but your application will still use them (of course) and compiler warnings will still appear in your build logs.

This can be a function that accepts an object of attributes on a <style> tag (like that passed to a Svelte preprocessor) and returns whether to ignore the style block for the purposes of linting.

The default is to not ignore any styles.

Using the CLI

It's probably a good idea to make sure you can lint from the command line before proceeding with configuring your editor.

Using this with the command line eslint tool shouldn't require any special actions. Just remember that if you are running eslint on a directory, you need to pass it the --ext flag to tell it which nonstandard file extensions you want to lint.

Integrations

See INTEGRATIONS.md for how to use this plugin with your text editor.

License

MIT