migration.md

Migration Guide

From eslint-plugin-svelte3

You can not use both eslint-plugin-svelte3 and eslint-plugin-svelte at same time. So before start to use this plugin, you need to remove eslint-plugin-svelte3's stuff from both package.json and .eslintrc.*.

Note: If you want to know difference between eslint-plugin-svelte and eslint-plugin-svelte3, Please read the reason for deprecating eslint-plugin-svelte3 in eslint-plugin-svelte3 README.

Note: If you're using TypeScript, maybe you get Parsing error: "parserOptions.project" has been set for @typescript-eslint/parser. error at some configuration files.
In this case, please refer this GitHub comment to solve it.

From eslint-plugin-svelte v1 To v2

eslint-plugin-svelte v1 was an alias for eslint-plugin-svelte3, but eslint-plugin-svelte v2 is now an independent eslint-plugin.

If you want the previous behavior, replace it with eslint-plugin-svelte3.

From @ota-meshi/eslint-plugin-svelte

@ota-meshi/eslint-plugin-svelte has been renamed to eslint-plugin-svelte.
Therefore, you need to replace the package name, and the presets, rules, and settings specified in the configuration.

• package.json
  Replace the package name.

  -  "@ota-meshi/eslint-plugin-svelte": "^0.X.X"
  +  "eslint-plugin-svelte": "^X.X.X"

• .eslintrc.*
  Replace @ota-meshi/svelte with svelte as a string.
  Examples:

  • Presets

      "extends": [
    -    "plugin:@ota-meshi/svelte/recommended"
    +    "plugin:svelte/recommended"
      ],

  • Rules

      "rules": {
    -    "@ota-meshi/svelte/no-dupe-else-if-blocks": "error",
    +    "svelte/no-dupe-else-if-blocks": "error",
    -    "@ota-meshi/svelte/button-has-type": "error",
    +    "svelte/button-has-type": "error",
      },

  • settings

      "settings": {
    -    "@ota-meshi/svelte": { ... }
    +    "svelte": { ... }
      },

From eslint-plugin-svelte v2 To v3

This section explains the necessary changes when upgrading from eslint-plugin-svelte v2 to v3.
v3 includes support for ESLint Flat Config only, changes to the recommended rule set, and other breaking changes.

---

Breaking Changes

1. Minimum Node.js Version Requirement

v3 requires one of the following Node.js versions:

• ^18.20.4
• ^20.18.0
• >=22.10.0

2. ESLint Flat Config Only

• .eslintrc.js and .eslintrc.json are no longer supported.
• You must use Flat Config (eslint.config.js).
• See README for more details.

3. ESLint Version Requirement

• v3 requires ESLint 8.57.1 or later (including v9.x).

4. Changes to Recommended Rule Set

• The following rules are now included in recommended:
  • svelte/infinite-reactive-loop
  • svelte/no-dom-manipulating
  • svelte/no-dupe-on-directives
  • svelte/no-reactive-reassign
  • svelte/require-event-dispatcher-types
  • Many others (See Changelog for more details)
• svelte/valid-compile has been removed from recommended.

5. Deprecated Rules

• svelte/no-dynamic-slot-name is deprecated.
• svelte/no-goto-without-base is deprecated and replaced with svelte/no-navigation-without-base.

---

New Features & Improvements

1. Support for Svelte 5

• Rules such as no-not-function-handler and valid-prop-names-in-kit-pages now support Svelte 5.

2. New Rules

• consistent-selector-style: Enforce consistent selector styles.
• no-useless-children-snippet: Prevent unnecessary {@children} usage.
• prefer-const: Prefer const over let.
• no-navigation-without-base: Ensure proper usage of goto().

---

Migration Steps

1. Upgrade Package

npm install eslint-plugin-svelte@3

2. Check Node.js Version

node -v

• Ensure it is v18.20.4 or later.

3. Check ESLint Version

npx eslint -v

• Ensure it is 8.57.1 or later (or 9.x).

4. Use Flat Config (eslint.config.js)

• Remove .eslintrc.js and migrate to eslint.config.js.

5. Apply the Updated Recommended Rules

• If using recommended, check the impact of newly added rules.

6. Replace Deprecated Rules

• Replace no-goto-without-base with no-navigation-without-base.