fix: use .ts/.tsx extension for internal virtual .js/.jsx codegen files

packages/vue-language-core/src/plugins/vue-tsx.ts

@@ -24,7 +24,7 @@ const plugin: VueLanguagePlugin = (ctx) => {
 			const tsx = useTsx(fileName, sfc);
 			const fileNames: string[] = [];
 
-			if (['js', 'ts', 'jsx', 'tsx'].includes(tsx.lang.value)) {
+			if (['ts', 'tsx'].includes(tsx.lang.value)) {
 				fileNames.push(fileName + '.' + tsx.lang.value);
 			}
 
@@ -117,10 +117,16 @@ export default plugin;
 function createTsx(fileName: string, _sfc: Sfc, { vueCompilerOptions, compilerOptions, codegenStack }: Parameters<VueLanguagePlugin>[0]) {
 
 	const lang = computed(() => {
-		return !_sfc.script && !_sfc.scriptSetup ? 'ts'
-			: _sfc.scriptSetup && _sfc.scriptSetup.lang !== 'js' ? _sfc.scriptSetup.lang
-				: _sfc.script && _sfc.script.lang !== 'js' ? _sfc.script.lang
-					: 'js';
+		let lang = 'ts';
+
+		if (_sfc.scriptSetup && _sfc.scriptSetup.lang !== 'js') {
+			lang = _sfc.scriptSetup.lang;
+		} else if (_sfc.script && _sfc.script.lang !== 'js') {
+			lang = _sfc.script.lang;
+		}
+
+		// Normalize 'js*' to 'ts*' as generated files are technically written in TypeScript.
+		return lang.replace(/^js/, 'ts');
 	});
 	const scriptRanges = computed(() =>
 		_sfc.scriptAst

packages/vue-test-workspace/vue-tsc/non-strict-template/#3121/main.vue

@@ -4,8 +4,10 @@
       v-for="col in slotFilters"
       :key="col"
       #[`filter-cell-${col}`]="{ column }"
-    ></template>
+    >{{ column }}</template>
   </Foo>
 </template>
 
-<script setup></script>
+<script setup>
+const slotFilters = [1, 2]
+</script>

packages/vue-test-workspace/vue-tsc/non-strict-template/#3353/main.vue

@@ -1,3 +1,4 @@
 <script>
+// @ts-expect-error
 ''.at('0');
 </script>