feat(no-unnecessary-state-wrap): support string array in allowReassign, default to ['SvelteSet'], and improve messages

docs/rules/no-unnecessary-state-wrap.md

@@ -66,14 +66,17 @@ Therefore, wrapping them with `$state` is unnecessary and can lead to confusion.
     "error",
     {
       "additionalReactiveClasses": [],
-      "allowReassign": false
+      "allowReassign": ["SvelteSet"]
     }
   ]
 }
 ```
 
 - `additionalReactiveClasses` ... An array of class names that should also be considered reactive. This is useful when you have custom classes that are inherently reactive. Default is `[]`.
-- `allowReassign` ... If `true`, allows `$state` wrapping of reactive classes when the variable is reassigned. Default is `false`.
+- `allowReassign` ... Can be either a boolean or an array of class names:
+  - If `true`, allows `$state` wrapping of any reactive classes when the variable is reassigned.
+  - If an array, allows `$state` wrapping for the specified reactive classes when the variable is reassigned.
+  - Default is `["SvelteSet"]`.
 
 ### Examples with Options
 
@@ -97,13 +100,36 @@ Therefore, wrapping them with `$state` is unnecessary and can lead to confusion.
 ```svelte
 <script>
   /* eslint svelte/no-unnecessary-state-wrap: ["error", { "allowReassign": true }] */
-  import { SvelteSet } from 'svelte/reactivity';
+  import { SvelteSet, SvelteMap } from 'svelte/reactivity';
 
   // ✓ GOOD
   let set1 = $state(new SvelteSet());
   set1 = new SvelteSet([1, 2, 3]); // Variable is reassigned
 
+  let map1 = $state(new SvelteMap());
+  map1 = new SvelteMap(); // Variable is reassigned
+
+  // ✗ BAD
+  const set2 = $state(new SvelteSet()); // const cannot be reassigned
+  let set3 = $state(new SvelteSet()); // Variable is never reassigned
+</script>
+```
+
+#### `allowReassign` as array
+
+```svelte
+<script>
+  /* eslint svelte/no-unnecessary-state-wrap: ["error", { "allowReassign": ["SvelteSet"] }] */
+  import { SvelteSet, SvelteMap } from 'svelte/reactivity';
+
+  // ✓ GOOD
+  let set = $state(new SvelteSet());
+  set = new SvelteSet([1, 2, 3]); // SvelteSet is in allowReassign and variable is reassigned
+
   // ✗ BAD
+  let map = $state(new SvelteMap()); // SvelteMap is not in allowReassign
+  map = new SvelteMap();
+
   const set2 = $state(new SvelteSet()); // const cannot be reassigned
   let set3 = $state(new SvelteSet()); // Variable is never reassigned
 </script>

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

@@ -526,7 +526,7 @@ type SvelteNoUnknownStyleDirectiveProperty = []|[{
 // ----- svelte/no-unnecessary-state-wrap -----
 type SvelteNoUnnecessaryStateWrap = []|[{
   additionalReactiveClasses?: string[]
-  allowReassign?: boolean
+  allowReassign?: (boolean | string[])
 }]
 // ----- svelte/no-unused-class-name -----
 type SvelteNoUnusedClassName = []|[{

packages/eslint-plugin-svelte/src/rules/no-unnecessary-state-wrap.ts

@@ -30,15 +30,28 @@ export default createRule('no-unnecessary-state-wrap', {
 						uniqueItems: true
 					},
 					allowReassign: {
-						type: 'boolean'
+						oneOf: [
+							{
+								type: 'boolean'
+							},
+							{
+								type: 'array',
+								items: {
+									type: 'string'
+								},
+								uniqueItems: true
+							}
+						]
 					}
 				},
 				additionalProperties: false
 			}
 		],
 		messages: {
-			unnecessaryStateWrap: '{{className}} is already reactive, $state wrapping is unnecessary.',
-			suggestRemoveStateWrap: 'Remove unnecessary $state wrapping'
+			unnecessaryStateWrap:
+				'{{className}} is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).',
+			suggestRemoveStateWrap:
+				'Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).'
 		},
 		type: 'suggestion',
 		hasSuggestions: true,
@@ -52,7 +65,7 @@ export default createRule('no-unnecessary-state-wrap', {
 	create(context) {
 		const options = context.options[0] ?? {};
 		const additionalReactiveClasses = options.additionalReactiveClasses ?? [];
-		const allowReassign = options.allowReassign ?? false;
+		const allowReassign = options.allowReassign ?? ['SvelteSet'];
 		const { globalScope } = context.sourceCode.scopeManager;
 		if (globalScope == null) {
 			return {};
@@ -91,13 +104,27 @@ export default createRule('no-unnecessary-state-wrap', {
 			});
 		}
 
+		function isAllowedReassign(className: string, identifier?: TSESTree.Identifier): boolean {
+			if (!identifier) return false;
+
+			if (typeof allowReassign === 'boolean') {
+				return allowReassign && isReassigned(identifier);
+			}
+
+			return (
+				Array.isArray(allowReassign) &&
+				allowReassign.includes(className) &&
+				isReassigned(identifier)
+			);
+		}
+
 		function reportUnnecessaryStateWrap(
 			stateNode: TSESTree.Node,
 			targetNode: TSESTree.Node,
 			className: string,
 			identifier?: TSESTree.Identifier
 		) {
-			if (allowReassign && identifier && isReassigned(identifier)) {
+			if (isAllowedReassign(className, identifier)) {
 				return;
 			}
 

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/additional-class-errors.yaml

@@ -1,8 +1,8 @@
-- message: CustomReactiveClass1 is already reactive, $state wrapping is unnecessary.
+- message: CustomReactiveClass1 is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 5
   column: 25
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -15,11 +15,11 @@
         	// Regular state usage is still valid
         	const regularState = $state(42);
         </script>
-- message: CustomReactiveClass2 is already reactive, $state wrapping is unnecessary.
+- message: CustomReactiveClass2 is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 6
   column: 25
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/allow-reassign-array-config.json

@@ -0,0 +1,7 @@
+{
+	"options": [
+		{
+			"allowReassign": ["SvelteSet"]
+		}
+	]
+}

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/allow-reassign-array-errors.yaml

@@ -0,0 +1,20 @@
+- message: SvelteMap is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
+  line: 11
+  column: 19
+  suggestions:
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
+      messageId: suggestRemoveStateWrap
+      output: |
+        <script>
+        	import { SvelteSet, SvelteMap } from 'svelte/reactivity';
+
+        	// This should NOT be reported as unnecessary $state wrapping
+        	// because SvelteSet is in the allowReassign array and is reassigned
+        	let set = $state(new SvelteSet());
+        	set = new SvelteSet([1, 2, 3]);
+
+        	// This should be reported as unnecessary $state wrapping
+        	// because SvelteMap is not in the allowReassign array
+        	let map = new SvelteMap();
+        	map = new SvelteMap();
+        </script>

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/allow-reassign-array-input.svelte

@@ -0,0 +1,13 @@
+<script>
+	import { SvelteSet, SvelteMap } from 'svelte/reactivity';
+
+	// This should NOT be reported as unnecessary $state wrapping
+	// because SvelteSet is in the allowReassign array and is reassigned
+	let set = $state(new SvelteSet());
+	set = new SvelteSet([1, 2, 3]);
+
+	// This should be reported as unnecessary $state wrapping
+	// because SvelteMap is not in the allowReassign array
+	let map = $state(new SvelteMap());
+	map = new SvelteMap();
+</script>

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/allow-reassign-errors.yaml

@@ -1,8 +1,8 @@
-- message: SvelteSet is already reactive, $state wrapping is unnecessary.
+- message: SvelteSet is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 6
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -13,11 +13,11 @@
         	const set = new SvelteSet();
         	let map = $state(new SvelteMap());
         </script>
-- message: SvelteMap is already reactive, $state wrapping is unnecessary.
+- message: SvelteMap is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 7
   column: 19
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/basic-errors.yaml

@@ -1,8 +1,8 @@
-- message: SvelteSet is already reactive, $state wrapping is unnecessary.
+- message: SvelteSet is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 12
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -27,11 +27,11 @@
         	const regularState = $state(42);
         	const stateObject = $state({ foo: 'bar' });
         </script>
-- message: SvelteMap is already reactive, $state wrapping is unnecessary.
+- message: SvelteMap is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 13
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -56,11 +56,11 @@
         	const regularState = $state(42);
         	const stateObject = $state({ foo: 'bar' });
         </script>
-- message: SvelteURL is already reactive, $state wrapping is unnecessary.
+- message: SvelteURL is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 14
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -85,11 +85,11 @@
         	const regularState = $state(42);
         	const stateObject = $state({ foo: 'bar' });
         </script>
-- message: SvelteURLSearchParams is already reactive, $state wrapping is unnecessary.
+- message: SvelteURLSearchParams is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 15
   column: 24
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -114,11 +114,11 @@
         	const regularState = $state(42);
         	const stateObject = $state({ foo: 'bar' });
         </script>
-- message: SvelteDate is already reactive, $state wrapping is unnecessary.
+- message: SvelteDate is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 16
   column: 22
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>
@@ -143,11 +143,11 @@
         	const regularState = $state(42);
         	const stateObject = $state({ foo: 'bar' });
         </script>
-- message: MediaQuery is already reactive, $state wrapping is unnecessary.
+- message: MediaQuery is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 17
   column: 28
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: |
         <script>

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unnecessary-state-wrap/invalid/import-alias-errors.yaml

@@ -1,8 +1,8 @@
-- message: SvelteSet is already reactive, $state wrapping is unnecessary.
+- message: SvelteSet is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 5
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: >
         <script>
@@ -12,11 +12,11 @@
         	const set = new CustomSet();
         	const map = $state(new CustomMap());
         </script>
-- message: SvelteMap is already reactive, $state wrapping is unnecessary.
+- message: SvelteMap is already reactive. `$state` wrapping is unnecessary. Update it with mutations (e.g., .add(), .delete(), .push(), .splice()).
   line: 6
   column: 21
   suggestions:
-    - desc: Remove unnecessary $state wrapping
+    - desc: Remove the unnecessary `$state` and update the value via mutations (e.g., .add(), .delete(), .push(), .splice()).
       messageId: suggestRemoveStateWrap
       output: >
         <script>