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ESLint plugin for Svelte using AST

Package Exports

    This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (eslint-plugin-svelte) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

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    eslint-plugin-svelte

    ESLint plugin for Svelte using AST

    Live DemoDocumentationDiscord

    Introduction

    eslint-plugin-svelte is the official ESLint plugin for Svelte.
    It leverages the AST generated by svelte-eslint-parser to provide custom linting for Svelte.
    Note that eslint-plugin-svelte and svelte-eslint-parser cannot be used alongside eslint-plugin-svelte3.

    Installation

    npm install --save-dev svelte eslint eslint-plugin-svelte globals

    [!NOTE]

    Requirements:

    • ESLint v8.57.1, v9.0.0, and above
    • Node.js v18.20.4, v20.18.0, v22.10.0, and above

    Usage

    Use the eslint.config.js file to configure rules. For more details, see the ESLint documentation.

    Configuration

    JavaScript project

    // eslint.config.js
    import js from '@eslint/js';
    import svelte from 'eslint-plugin-svelte';
    import globals from 'globals';
    import svelteConfig from './svelte.config.js';
    
    /** @type {import('eslint').Linter.Config[]} */
    export default [
      js.configs.recommended,
      ...svelte.configs.recommended,
      {
        languageOptions: {
          globals: {
            ...globals.browser,
            ...globals.node // Add this if you are using SvelteKit in non-SPA mode
          }
        }
      },
      {
        files: ['**/*.svelte', '**/*.svelte.js'],
        languageOptions: {
          parserOptions: {
            // We recommend importing and specifying svelte.config.js.
            // By doing so, some rules in eslint-plugin-svelte will automatically read the configuration and adjust their behavior accordingly.
            // While certain Svelte settings may be statically loaded from svelte.config.js even if you don’t specify it,
            // explicitly specifying it ensures better compatibility and functionality.
            svelteConfig
          }
        }
      },
      {
        rules: {
          // Override or add rule settings here, such as:
          // 'svelte/rule-name': 'error'
        }
      }
    ];

    TypeScript project

    npm install --save-dev typescript-eslint
    // eslint.config.js
    import js from '@eslint/js';
    import svelte from 'eslint-plugin-svelte';
    import globals from 'globals';
    import ts from 'typescript-eslint';
    import svelteConfig from './svelte.config.js';
    
    export default ts.config(
      js.configs.recommended,
      ...ts.configs.recommended,
      ...svelte.configs.recommended,
      {
        languageOptions: {
          globals: {
            ...globals.browser,
            ...globals.node
          }
        }
      },
      {
        files: ['**/*.svelte', '**/*.svelte.ts', '**/*.svelte.js'],
        // See more details at: https://typescript-eslint.io/packages/parser/
        languageOptions: {
          parserOptions: {
            projectService: true,
            extraFileExtensions: ['.svelte'], // Add support for additional file extensions, such as .svelte
            parser: ts.parser,
            // Specify a parser for each language, if needed:
            // parser: {
            //   ts: ts.parser,
            //   js: espree,    // Use espree for .js files (add: import espree from 'espree')
            //   typescript: ts.parser
            // },
    
            // We recommend importing and specifying svelte.config.js.
            // By doing so, some rules in eslint-plugin-svelte will automatically read the configuration and adjust their behavior accordingly.
            // While certain Svelte settings may be statically loaded from svelte.config.js even if you don’t specify it,
            // explicitly specifying it ensures better compatibility and functionality.
            svelteConfig
          }
        }
      },
      {
        rules: {
          // Override or add rule settings here, such as:
          // 'svelte/rule-name': 'error'
        }
      }
    );

    [!WARNING] The TypeScript parser uses a singleton internally, meaning it only respects the options provided during its initial initialization. If you try to change the options for a different file or override them later, the parser will ignore the new options, which may lead to errors. For more context, see typescript-eslint/typescript-eslint#6778.

    Available Configurations

    This plugin provides the following configurations:

    • eslintPluginSvelte.configs.base ... Enables correct Svelte parsing.
    • eslintPluginSvelte.configs.recommended ... Includes base configuration, plus rules to prevent errors or unintended behavior.
    • eslintPluginSvelte.configs.prettier ... Disables rules that may conflict with Prettier. You still need to configure Prettier to work with Svelte manually, for example, by using prettier-plugin-svelte.
    • eslintPluginSvelte.configs.all ... Includes all available rules. Note: This configuration is not recommended for production use, as it changes with every minor and major version of eslint-plugin-svelte. Use at your own risk.

    For more details, see the rule list to explore the rules provided by this plugin.

    settings.svelte

    You can customize the behavior of this plugin using specific settings.

    // eslint.config.js
    export default [
      // ...
      {
        settings: {
          svelte: {
            // Specifies an array of rules to ignore reports within the template.
            // For example, use this to disable rules in the template that may produce unavoidable false positives.
            ignoreWarnings: [
              '@typescript-eslint/no-unsafe-assignment',
              '@typescript-eslint/no-unsafe-member-access'
            ],
            // Specifies options for Svelte compilation.
            // This affects rules that rely on Svelte compilation,
            // such as svelte/valid-compile and svelte/no-unused-svelte-ignore.
            // Note that this setting does not impact ESLint’s custom parser.
            compileOptions: {
              // Specifies options related to PostCSS. You can disable the PostCSS processing by setting it to false.
              postcss: {
                // Specifies the path to the directory that contains the PostCSS configuration.
                configFilePath: './path/to/my/postcss.config.js'
              }
            },
            // Even if settings.svelte.kit is not specified, the rules will attempt to load information from svelte.config.js.
            // However, if the default behavior does not work as expected, you should specify settings.svelte.kit explicitly.
            // If you are using SvelteKit with a non-default configuration, you need to set the following options.
            // The schema is a subset of SvelteKit’s configuration, so refer to the SvelteKit documentation for more details.
            // https://svelte.dev/docs/kit/configuration
            kit: {
              files: {
                routes: 'src/routes'
              }
            }
          }
        }
      }
      // ...
    ];

    Editor Integrations

    Visual Studio Code
    Install dbaeumer.vscode-eslint.
    Configure .svelte files in .vscode/settings.json:

    {
      "eslint.validate": ["javascript", "javascriptreact", "svelte"]
    }

    Migration Guide

    If you’re migrating from eslint-plugin-svelte v1 or @ota-meshi/eslint-plugin-svelte, see the migration guide.

    Versioning Policy

    This project follows Semantic Versioning. Unlike ESLint’s versioning policy, new rules may be added to the recommended config in minor releases. If these rules cause unwanted warnings, you can disable them.

    Rules

    🔧 Indicates that the rule is fixable, and using --fix option on the command line can automatically fix some of the reported problems.
    💡 Indicates that some problems reported by the rule are manually fixable by editor suggestions.
    ⭐ Indicates that the rule is included in the plugin:svelte/recommended config.

    Possible Errors

    These rules relate to possible syntax or logic errors in Svelte code:

    Rule ID Description
    svelte/infinite-reactive-loop Svelte runtime prevents calling the same reactive statement twice in a microtask. But between different microtask, it doesn't prevent.
    svelte/no-dom-manipulating disallow DOM manipulating
    svelte/no-dupe-else-if-blocks disallow duplicate conditions in {#if} / {:else if} chains
    svelte/no-dupe-on-directives disallow duplicate on: directives
    svelte/no-dupe-style-properties disallow duplicate style properties
    svelte/no-dupe-use-directives disallow duplicate use: directives
    svelte/no-not-function-handler disallow use of not function in event handler
    svelte/no-object-in-text-mustaches disallow objects in text mustache interpolation
    svelte/no-raw-special-elements Checks for invalid raw HTML elements ⭐🔧
    svelte/no-reactive-reassign disallow reassigning reactive values
    svelte/no-shorthand-style-property-overrides disallow shorthand style properties that override related longhand properties
    svelte/no-store-async disallow using async/await inside svelte stores because it causes issues with the auto-unsubscribing features
    svelte/no-unknown-style-directive-property disallow unknown style:property
    svelte/require-store-callbacks-use-set-param store callbacks must use set param
    svelte/require-store-reactive-access disallow to use of the store itself as an operand. Need to use $ prefix or get function. ⭐🔧
    svelte/valid-compile disallow warnings when compiling.
    svelte/valid-style-parse require valid style element parsing

    Security Vulnerability

    These rules relate to security vulnerabilities in Svelte code:

    Rule ID Description
    svelte/no-at-html-tags disallow use of {@html} to prevent XSS attack
    svelte/no-target-blank disallow target="_blank" attribute without rel="noopener noreferrer"

    Best Practices

    These rules relate to better ways of doing things to help you avoid problems:

    Rule ID Description
    svelte/block-lang disallows the use of languages other than those specified in the configuration for the lang attribute of <script> and <style> blocks. 💡
    svelte/button-has-type disallow usage of button without an explicit type attribute
    svelte/no-at-debug-tags disallow the use of {@debug}
    svelte/no-ignored-unsubscribe disallow ignoring the unsubscribe method returned by the subscribe() on Svelte stores.
    svelte/no-immutable-reactive-statements disallow reactive statements that don't reference reactive values.
    svelte/no-inline-styles disallow attributes and directives that produce inline styles
    svelte/no-inspect Warns against the use of $inspect directive
    svelte/no-reactive-functions it's not necessary to define functions in reactive statements ⭐💡
    svelte/no-reactive-literals don't assign literal values in reactive statements ⭐💡
    svelte/no-svelte-internal svelte/internal will be removed in Svelte 6.
    svelte/no-unused-class-name disallow the use of a class in the template without a corresponding style
    svelte/no-unused-svelte-ignore disallow unused svelte-ignore comments
    svelte/no-useless-children-snippet disallow explicit children snippet where it's not needed
    svelte/no-useless-mustaches disallow unnecessary mustache interpolations ⭐🔧
    svelte/prefer-const Require const declarations for variables that are never reassigned after declared 🔧
    svelte/prefer-destructured-store-props destructure values from object stores for better change tracking & fewer redraws 💡
    svelte/require-each-key require keyed {#each} block
    svelte/require-event-dispatcher-types require type parameters for createEventDispatcher
    svelte/require-optimized-style-attribute require style attributes that can be optimized
    svelte/require-stores-init require initial value in store
    svelte/valid-each-key enforce keys to use variables defined in the {#each} block

    Stylistic Issues

    These rules relate to style guidelines, and are therefore quite subjective:

    Rule ID Description
    svelte/consistent-selector-style enforce a consistent style for CSS selectors
    svelte/derived-has-same-inputs-outputs derived store should use same variable names between values and callback
    svelte/first-attribute-linebreak enforce the location of first attribute 🔧
    svelte/html-closing-bracket-new-line Require or disallow a line break before tag's closing brackets 🔧
    svelte/html-closing-bracket-spacing require or disallow a space before tag's closing brackets 🔧
    svelte/html-quotes enforce quotes style of HTML attributes 🔧
    svelte/html-self-closing enforce self-closing style 🔧
    svelte/indent enforce consistent indentation 🔧
    svelte/max-attributes-per-line enforce the maximum number of attributes per line 🔧
    svelte/mustache-spacing enforce unified spacing in mustache 🔧
    svelte/no-extra-reactive-curlies disallow wrapping single reactive statements in curly braces 💡
    svelte/no-restricted-html-elements disallow specific HTML elements
    svelte/no-spaces-around-equal-signs-in-attribute disallow spaces around equal signs in attribute 🔧
    svelte/prefer-class-directive require class directives instead of ternary expressions 🔧
    svelte/prefer-style-directive require style directives instead of style attribute 🔧
    svelte/shorthand-attribute enforce use of shorthand syntax in attribute 🔧
    svelte/shorthand-directive enforce use of shorthand syntax in directives 🔧
    svelte/sort-attributes enforce order of attributes 🔧
    svelte/spaced-html-comment enforce consistent spacing after the <!-- and before the --> in a HTML comment 🔧

    Extension Rules

    These rules extend the rules provided by ESLint itself, or other plugins to work well in Svelte:

    Rule ID Description
    svelte/no-inner-declarations disallow variable or function declarations in nested blocks
    svelte/no-trailing-spaces disallow trailing whitespace at the end of lines 🔧

    SvelteKit

    These rules relate to SvelteKit and its best Practices.

    Rule ID Description
    svelte/no-export-load-in-svelte-module-in-kit-pages disallow exporting load functions in *.svelte module in SvelteKit page components.
    svelte/no-navigation-without-base disallow using navigation (links, goto, pushState, replaceState) without the base path
    svelte/valid-prop-names-in-kit-pages disallow props other than data or errors in SvelteKit page components.

    Experimental

    ⚠️ These rules are considered experimental and may change or be removed in the future:

    Rule ID Description
    svelte/experimental-require-slot-types require slot type declaration using the $$Slots interface
    svelte/experimental-require-strict-events require the strictEvents attribute on <script> tags

    System

    These rules relate to this plugin works:

    Rule ID Description
    svelte/comment-directive support comment-directives in HTML template
    svelte/system system rule for working this plugin

    Deprecated

    • ⚠️ We're going to remove deprecated rules in the next major release. Please migrate to successor/new rules.
    • 😇 We don't fix bugs which are in deprecated rules since we don't have enough resources.
    Rule ID Replaced by
    svelte/@typescript-eslint/no-unnecessary-condition This rule is no longer needed when using svelte-eslint-parser>=v0.19.0.
    svelte/no-dynamic-slot-name Now Svelte compiler itself throws an compile error.
    svelte/no-goto-without-base svelte/no-navigation-without-base

    Contributing

    Contributions are welcome! Please open an issue or submit a PR. For more details, see CONTRIBUTING.md.
    Refer to svelte-eslint-parser for AST details.

    License

    See LICENSE (MIT).