fix(compiler-sfc): fix dev regression for dot / namespace component usage

close #9947

packages/compiler-sfc/__tests__/compileScript/__snapshots__/importUsageCheck.spec.ts.snap

@@ -79,6 +79,21 @@ return { get FooBar() { return FooBar }, get foo() { return foo }, get bar() { r
 })"
 `;
 
+exports[`import namespace 1`] = `
+"import { defineComponent as _defineComponent } from 'vue'
+import * as Foo from './foo'
+    
+export default /*#__PURE__*/_defineComponent({
+  setup(__props, { expose: __expose }) {
+  __expose();
+
+      
+return { get Foo() { return Foo } }
+}
+
+})"
+`;
+
 exports[`js template string interpolations 1`] = `
 "import { defineComponent as _defineComponent } from 'vue'
 import { VAR, VAR2, VAR3 } from './x'

packages/compiler-sfc/__tests__/compileScript/importUsageCheck.spec.ts

@@ -219,3 +219,17 @@ test('property access (whitespace)', () => {
   expect(content).toMatch('return { get Foo() { return Foo } }')
   assertCode(content)
 })
+
+// #9974
+test('namespace / dot component usage', () => {
+  const { content } = compile(`
+    <script setup lang="ts">
+      import * as Foo from './foo'
+    </script>
+    <template>
+      <Foo.Bar />
+    </template>
+    `)
+  expect(content).toMatch('return { get Foo() { return Foo } }')
+  assertCode(content)
+})

packages/compiler-sfc/src/script/importUsageCheck.ts

@@ -16,12 +16,12 @@ import { camelize, capitalize, isBuiltInDirective } from '@vue/shared'
  * when not using inline mode.
  */
 export function isImportUsed(local: string, sfc: SFCDescriptor): boolean {
-  return resolveTemplateUsageCheckString(sfc).has(local)
+  return resolveTemplateUsedIdentifiers(sfc).has(local)
 }
 
 const templateUsageCheckCache = createCache<Set<string>>()
 
-function resolveTemplateUsageCheckString(sfc: SFCDescriptor) {
+function resolveTemplateUsedIdentifiers(sfc: SFCDescriptor): Set<string> {
   const { content, ast } = sfc.template!
   const cached = templateUsageCheckCache.get(content)
   if (cached) {
@@ -35,12 +35,14 @@ function resolveTemplateUsageCheckString(sfc: SFCDescriptor) {
   function walk(node: TemplateChildNode) {
     switch (node.type) {
       case NodeTypes.ELEMENT:
+        let tag = node.tag
+        if (tag.includes('.')) tag = tag.split('.')[0].trim()
         if (
-          !parserOptions.isNativeTag!(node.tag) &&
-          !parserOptions.isBuiltInComponent!(node.tag)
+          !parserOptions.isNativeTag!(tag) &&
+          !parserOptions.isBuiltInComponent!(tag)
         ) {
-          ids.add(camelize(node.tag))
-          ids.add(capitalize(camelize(node.tag)))
+          ids.add(camelize(tag))
+          ids.add(capitalize(camelize(tag)))
         }
         for (let i = 0; i < node.props.length; i++) {
           const prop = node.props[i]