fix(no-unused-svelte-ignore): ignore reactive-component warnings (#1208)

Author: ota-meshi

.changeset/three-turkeys-marry.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-svelte": patch
+---
+
+fix(no-unused-svelte-ignore): ignore reactive-component warnings

packages/eslint-plugin-svelte/src/rules/no-unused-svelte-ignore.ts

@@ -2,6 +2,8 @@ import { getSvelteCompileWarnings } from '../shared/svelte-compile-warns/index.j
 import { createRule } from '../utils/index.js';
 import type { IgnoreItem } from '../shared/svelte-compile-warns/ignore-comment.js';
 import { getSvelteIgnoreItems } from '../shared/svelte-compile-warns/ignore-comment.js';
+import { VERSION as SVELTE_VERSION } from 'svelte/compiler';
+import semver from 'semver';
 
 export default createRule('no-unused-svelte-ignore', {
 	meta: {
@@ -46,6 +48,14 @@ export default createRule('no-unused-svelte-ignore', {
 		}
 
 		for (const unused of warnings.unusedIgnores) {
+			if (unused.code === 'reactive-component' && semver.satisfies(SVELTE_VERSION, '<5')) {
+				// Svelte v4 `reactive-component` warnings are not emitted
+				// when we use the `generate: false` compiler option.
+				// This is probably not the intended behavior of Svelte v4, but it's not going to be fixed,
+				// so as a workaround we'll ignore the `reactive-component` warnings.
+				// See https://github.com/sveltejs/eslint-plugin-svelte/issues/1192
+				continue;
+			}
 			context.report({
 				loc: {
 					start: sourceCode.getLocFromIndex(unused.range[0]),

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unused-svelte-ignore/valid/reactive-component-input.svelte

@@ -0,0 +1,15 @@
+<script lang="ts">
+	import { onMount } from 'svelte'
+
+	let MyComponent: typeof import('./MyComponent.svelte').default | undefined
+	onMount(() => {
+		import('./MyComponent.svelte').then((component) => {
+			MyComponent = component.default
+		})
+	})
+</script>
+
+{#if MyComponent}
+	<!-- svelte-ignore reactive-component -->
+	<MyComponent />
+{/if}

packages/eslint-plugin-svelte/tests/fixtures/rules/no-unused-svelte-ignore/valid/reactive-component-requirements.json

@@ -0,0 +1,3 @@
+{
+	"svelte": "^4"
+}