feat: added the prefer-svelte-reactivity rule

.changeset/rich-colts-nail.md

@@ -0,0 +1,5 @@
+---
+'eslint-plugin-svelte': minor
+---
+
+feat: added the `prefer-svelte-reactivity` rule

README.md

@@ -273,6 +273,7 @@ These rules relate to possible syntax or logic errors in Svelte code:
 | [svelte/no-store-async](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-store-async/) | disallow using async/await inside svelte stores because it causes issues with the auto-unsubscribing features | :star: |
 | [svelte/no-top-level-browser-globals](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-top-level-browser-globals/) | disallow using top-level browser global variables |  |
 | [svelte/no-unknown-style-directive-property](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-unknown-style-directive-property/) | disallow unknown `style:property` | :star: |
+| [svelte/prefer-svelte-reactivity](https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-svelte-reactivity/) | disallow using built-in classes where a reactive alternative is provided by svelte/reactivity | :star: |
 | [svelte/require-store-callbacks-use-set-param](https://sveltejs.github.io/eslint-plugin-svelte/rules/require-store-callbacks-use-set-param/) | store callbacks must use `set` param | :bulb: |
 | [svelte/require-store-reactive-access](https://sveltejs.github.io/eslint-plugin-svelte/rules/require-store-reactive-access/) | disallow to use of the store itself as an operand. Need to use $ prefix or get function. | :star::wrench: |
 | [svelte/valid-compile](https://sveltejs.github.io/eslint-plugin-svelte/rules/valid-compile/) | disallow warnings when compiling. |  |

docs/rules.md

@@ -30,6 +30,7 @@ These rules relate to possible syntax or logic errors in Svelte code:
 | [svelte/no-store-async](./rules/no-store-async.md)                                               | disallow using async/await inside svelte stores because it causes issues with the auto-unsubscribing features                          | :star:         |
 | [svelte/no-top-level-browser-globals](./rules/no-top-level-browser-globals.md)                   | disallow using top-level browser global variables                                                                                      |                |
 | [svelte/no-unknown-style-directive-property](./rules/no-unknown-style-directive-property.md)     | disallow unknown `style:property`                                                                                                      | :star:         |
+| [svelte/prefer-svelte-reactivity](./rules/prefer-svelte-reactivity.md)                           | disallow using built-in classes where a reactive alternative is provided by svelte/reactivity                                          | :star:         |
 | [svelte/require-store-callbacks-use-set-param](./rules/require-store-callbacks-use-set-param.md) | store callbacks must use `set` param                                                                                                   | :bulb:         |
 | [svelte/require-store-reactive-access](./rules/require-store-reactive-access.md)                 | disallow to use of the store itself as an operand. Need to use $ prefix or get function.                                               | :star::wrench: |
 | [svelte/valid-compile](./rules/valid-compile.md)                                                 | disallow warnings when compiling.                                                                                                      |                |

docs/rules/prefer-svelte-reactivity.md

@@ -0,0 +1,68 @@
+---
+pageClass: 'rule-details'
+sidebarDepth: 0
+title: 'svelte/prefer-svelte-reactivity'
+description: 'disallow using built-in classes where a reactive alternative is provided by svelte/reactivity'
+---
+
+# svelte/prefer-svelte-reactivity
+
+> disallow using built-in classes where a reactive alternative is provided by svelte/reactivity
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> **_This rule has not been released yet._** </badge>
+- :gear: This rule is included in `"plugin:svelte/recommended"`.
+
+## :book: Rule Details
+
+The built-in `Date`, `Map`, `Set`, `URL` and `URLSearchParams` classes are often used in frontend code, however, their properties and methods are not reactive. Because of that, Svelte provides reactive versions of these 5 builtins as part of the "svelte/reactivity" package. This rule reports usage of the built-in versions in Svelte code.
+
+<!--eslint-skip-->
+
+```svelte
+<script>
+  /* eslint svelte/prefer-svelte-reactivity: "error" */
+
+  import {
+    SvelteDate,
+    SvelteMap,
+    SvelteSet,
+    SvelteURL,
+    SvelteURLSearchParams
+  } from 'svelte/reactivity';
+
+  /* ✓ GOOD */
+
+  const a = new SvelteDate(8.64e15);
+  const b = new SvelteMap([
+    [1, 'one'],
+    [2, 'two']
+  ]);
+  const c = new SvelteSet([1, 2, 1, 3, 3]);
+  const d = new SvelteURL('https://svelte.dev/');
+  const e = new SvelteURLSearchParams('foo=1&bar=2');
+
+  /* ✗ BAD */
+
+  const f = new Date(8.64e15);
+  const g = new Map([
+    [1, 'one'],
+    [2, 'two']
+  ]);
+  const h = new Set([1, 2, 1, 3, 3]);
+  const i = new URL('https://svelte.dev/');
+  const j = new URLSearchParams('foo=1&bar=2');
+</script>
+```
+
+## :wrench: Options
+
+Nothing.
+
+## :books: Further Reading
+
+- [svelte/reactivity documentation](https://svelte.dev/docs/svelte/svelte-reactivity)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/packages/eslint-plugin-svelte/src/rules/prefer-svelte-reactivity.ts)
+- [Test source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/packages/eslint-plugin-svelte/tests/src/rules/prefer-svelte-reactivity.ts)

packages/eslint-plugin-svelte/src/configs/flat/recommended.ts

@@ -37,6 +37,7 @@ const config: Linter.Config[] = [
 			'svelte/no-unused-svelte-ignore': 'error',
 			'svelte/no-useless-children-snippet': 'error',
 			'svelte/no-useless-mustaches': 'error',
+			'svelte/prefer-svelte-reactivity': 'error',
 			'svelte/prefer-writable-derived': 'error',
 			'svelte/require-each-key': 'error',
 			'svelte/require-event-dispatcher-types': 'error',

packages/eslint-plugin-svelte/src/rule-types.ts

@@ -316,6 +316,11 @@ export interface RuleOptions {
    * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-style-directive/
    */
   'svelte/prefer-style-directive'?: Linter.RuleEntry<[]>
+  /**
+   * disallow using built-in classes where a reactive alternative is provided by svelte/reactivity
+   * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-svelte-reactivity/
+   */
+  'svelte/prefer-svelte-reactivity'?: Linter.RuleEntry<[]>
   /**
    * Prefer using writable $derived instead of $state and $effect
    * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-writable-derived/

packages/eslint-plugin-svelte/src/rules/prefer-svelte-reactivity.ts

@@ -0,0 +1,246 @@
+import { ReferenceTracker } from '@eslint-community/eslint-utils';
+import { createRule } from '../utils/index.js';
+import type { TSESTree } from '@typescript-eslint/types';
+
+export default createRule('prefer-svelte-reactivity', {
+	meta: {
+		docs: {
+			description:
+				'disallow using built-in classes where a reactive alternative is provided by svelte/reactivity',
+			category: 'Possible Errors',
+			recommended: true
+		},
+		schema: [],
+		messages: {
+			mutableDateUsed:
+				'Found a mutable instance of the built-in Date class. Use SvelteDate instead.',
+			mutableMapUsed: 'Found a mutable instance of the built-in Map class. Use SvelteMap instead.',
+			mutableSetUsed: 'Found a mutable instance of the built-in Set class. Use SvelteSet instead.',
+			mutableURLUsed: 'Found a mutable instance of the built-in URL class. Use SvelteURL instead.',
+			mutableURLSearchParamsUsed:
+				'Found a mutable instance of the built-in URLSearchParams class. Use SvelteURLSearchParams instead.'
+		},
+		type: 'problem', // 'problem', or 'layout',
+		conditions: [
+			{
+				svelteVersions: ['5'],
+				svelteFileTypes: ['.svelte', '.svelte.[js|ts]']
+			}
+		]
+	},
+	create(context) {
+		return {
+			Program() {
+				const referenceTracker = new ReferenceTracker(context.sourceCode.scopeManager.globalScope!);
+				for (const { node, path } of referenceTracker.iterateGlobalReferences({
+					Date: {
+						[ReferenceTracker.CONSTRUCT]: true
+					},
+					Map: {
+						[ReferenceTracker.CONSTRUCT]: true
+					},
+					Set: {
+						[ReferenceTracker.CONSTRUCT]: true
+					},
+					URL: {
+						[ReferenceTracker.CONSTRUCT]: true
+					},
+					URLSearchParams: {
+						[ReferenceTracker.CONSTRUCT]: true
+					}
+				})) {
+					if (path[0] === 'Date' && isDateMutable(referenceTracker, node as TSESTree.Expression)) {
+						context.report({
+							messageId: 'mutableDateUsed',
+							node
+						});
+					}
+					if (path[0] === 'Map' && isMapMutable(referenceTracker, node as TSESTree.Expression)) {
+						context.report({
+							messageId: 'mutableMapUsed',
+							node
+						});
+					}
+					if (path[0] === 'Set' && isSetMutable(referenceTracker, node as TSESTree.Expression)) {
+						context.report({
+							messageId: 'mutableSetUsed',
+							node
+						});
+					}
+					if (path[0] === 'URL' && isURLMutable(referenceTracker, node as TSESTree.Expression)) {
+						context.report({
+							messageId: 'mutableURLUsed',
+							node
+						});
+					}
+					if (
+						path[0] === 'URLSearchParams' &&
+						isURLSearchParamsMutable(referenceTracker, node as TSESTree.Expression)
+					) {
+						context.report({
+							messageId: 'mutableURLSearchParamsUsed',
+							node
+						});
+					}
+				}
+			}
+		};
+	}
+});
+
+function isDateMutable(referenceTracker: ReferenceTracker, ctorNode: TSESTree.Expression): boolean {
+	return (
+		Array.from(
+			referenceTracker.iteratePropertyReferences(ctorNode, {
+				setDate: {
+					[ReferenceTracker.CALL]: true
+				},
+				setFullYear: {
+					[ReferenceTracker.CALL]: true
+				},
+				setHours: {
+					[ReferenceTracker.CALL]: true
+				},
+				setMilliseconds: {
+					[ReferenceTracker.CALL]: true
+				},
+				setMinutes: {
+					[ReferenceTracker.CALL]: true
+				},
+				setMonth: {
+					[ReferenceTracker.CALL]: true
+				},
+				setSeconds: {
+					[ReferenceTracker.CALL]: true
+				},
+				setTime: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCDate: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCFullYear: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCHours: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCMilliseconds: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCMinutes: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCMonth: {
+					[ReferenceTracker.CALL]: true
+				},
+				setUTCSeconds: {
+					[ReferenceTracker.CALL]: true
+				},
+				setYear: {
+					[ReferenceTracker.CALL]: true
+				}
+			})
+		).length > 0
+	);
+}
+
+function isMapMutable(referenceTracker: ReferenceTracker, ctorNode: TSESTree.Expression): boolean {
+	return (
+		Array.from(
+			referenceTracker.iteratePropertyReferences(ctorNode, {
+				clear: {
+					[ReferenceTracker.CALL]: true
+				},
+				delete: {
+					[ReferenceTracker.CALL]: true
+				},
+				set: {
+					[ReferenceTracker.CALL]: true
+				}
+			})
+		).length > 0
+	);
+}
+
+function isSetMutable(referenceTracker: ReferenceTracker, ctorNode: TSESTree.Expression): boolean {
+	return (
+		Array.from(
+			referenceTracker.iteratePropertyReferences(ctorNode, {
+				add: {
+					[ReferenceTracker.CALL]: true
+				},
+				clear: {
+					[ReferenceTracker.CALL]: true
+				},
+				delete: {
+					[ReferenceTracker.CALL]: true
+				}
+			})
+		).length > 0
+	);
+}
+
+function isURLMutable(referenceTracker: ReferenceTracker, ctorNode: TSESTree.Expression): boolean {
+	for (const { node } of referenceTracker.iteratePropertyReferences(ctorNode, {
+		hash: {
+			[ReferenceTracker.READ]: true
+		},
+		host: {
+			[ReferenceTracker.READ]: true
+		},
+		hostname: {
+			[ReferenceTracker.READ]: true
+		},
+		href: {
+			[ReferenceTracker.READ]: true
+		},
+		password: {
+			[ReferenceTracker.READ]: true
+		},
+		pathname: {
+			[ReferenceTracker.READ]: true
+		},
+		port: {
+			[ReferenceTracker.READ]: true
+		},
+		protocol: {
+			[ReferenceTracker.READ]: true
+		},
+		search: {
+			[ReferenceTracker.READ]: true
+		},
+		username: {
+			[ReferenceTracker.READ]: true
+		}
+	})) {
+		if (node.parent.type === 'AssignmentExpression') {
+			return true;
+		}
+	}
+	return false;
+}
+
+function isURLSearchParamsMutable(
+	referenceTracker: ReferenceTracker,
+	ctorNode: TSESTree.Expression
+): boolean {
+	return (
+		Array.from(
+			referenceTracker.iteratePropertyReferences(ctorNode, {
+				append: {
+					[ReferenceTracker.CALL]: true
+				},
+				delete: {
+					[ReferenceTracker.CALL]: true
+				},
+				set: {
+					[ReferenceTracker.CALL]: true
+				},
+				sort: {
+					[ReferenceTracker.CALL]: true
+				}
+			})
+		).length > 0
+	);
+}

packages/eslint-plugin-svelte/src/utils/rules.ts

@@ -62,6 +62,7 @@ import preferClassDirective from '../rules/prefer-class-directive.js';
 import preferConst from '../rules/prefer-const.js';
 import preferDestructuredStoreProps from '../rules/prefer-destructured-store-props.js';
 import preferStyleDirective from '../rules/prefer-style-directive.js';
+import preferSvelteReactivity from '../rules/prefer-svelte-reactivity.js';
 import preferWritableDerived from '../rules/prefer-writable-derived.js';
 import requireEachKey from '../rules/require-each-key.js';
 import requireEventDispatcherTypes from '../rules/require-event-dispatcher-types.js';
@@ -141,6 +142,7 @@ export const rules = [
 	preferConst,
 	preferDestructuredStoreProps,
 	preferStyleDirective,
+	preferSvelteReactivity,
 	preferWritableDerived,
 	requireEachKey,
 	requireEventDispatcherTypes,

packages/eslint-plugin-svelte/tests/fixtures/rules/prefer-svelte-reactivity/invalid/_requirements.json

@@ -0,0 +1,3 @@
+{
+	"svelte": ">=5.0.0"
+}

packages/eslint-plugin-svelte/tests/fixtures/rules/prefer-svelte-reactivity/invalid/date/setDate01-errors.yaml

@@ -0,0 +1,4 @@
+- message: Found a mutable instance of the built-in Date class. Use SvelteDate instead.
+  line: 2
+  column: 20
+  suggestions: null

packages/eslint-plugin-svelte/tests/fixtures/rules/prefer-svelte-reactivity/invalid/date/setDate01-input.svelte

@@ -0,0 +1,7 @@
+<script>
+  const variable = new Date(8.64e15);
+
+  variable.setDate(24);
+</script>
+
+{variable}

packages/eslint-plugin-svelte/tests/fixtures/rules/prefer-svelte-reactivity/invalid/date/setFullYear01-errors.yaml

@@ -0,0 +1,4 @@
+- message: Found a mutable instance of the built-in Date class. Use SvelteDate instead.
+  line: 2
+  column: 20
+  suggestions: null