fix(core): fix used templates are not deleted (#60459)

After running the control flow migration, used templates are not deleted.

PR Close #60459

packages/core/schematics/ng-generate/control-flow-migration/util.ts

@@ -385,10 +385,6 @@ export function calculateNesting(
   }
 }
 
-function escapeRegExp(val: string) {
-  return val.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
-}
-
 /**
  * determines if a given template string contains line breaks
  */
@@ -425,20 +421,48 @@ export function getTemplates(template: string): Map<string, Template> {
     const visitor = new TemplateCollector();
     visitAll(visitor, parsed.tree.rootNodes);
 
-    // count usages of each ng-template
     for (let [key, tmpl] of visitor.templates) {
-      const escapeKey = escapeRegExp(key.slice(1));
-      const regex = new RegExp(`[^a-zA-Z0-9-<(\']${escapeKey}\\W`, 'gm');
-      const matches = template.match(regex);
-      tmpl.count = matches?.length ?? 0;
+      tmpl.count = countTemplateUsage(parsed.tree.rootNodes, key);
       tmpl.generateContents(template);
     }
-
     return visitor.templates;
   }
   return new Map<string, Template>();
 }
 
+function countTemplateUsage(nodes: any[], templateName: string): number {
+  let count = 0;
+  let isReferencedInTemplateOutlet = false;
+
+  for (const node of nodes) {
+    if (node.attrs) {
+      for (const attr of node.attrs) {
+        if (attr.name === '*ngTemplateOutlet' && attr.value === templateName.slice(1)) {
+          isReferencedInTemplateOutlet = true;
+          break;
+        }
+
+        if (attr.name.trim() === templateName) {
+          count++;
+        }
+      }
+    }
+
+    if (node.children) {
+      if (node.name === 'for') {
+        for (const child of node.children) {
+          if (child.value?.includes(templateName.slice(1))) {
+            count++;
+          }
+        }
+      }
+      count += countTemplateUsage(node.children, templateName);
+    }
+  }
+
+  return isReferencedInTemplateOutlet ? count + 2 : count;
+}
+
 export function updateTemplates(
   template: string,
   templates: Map<string, Template>,
@@ -497,8 +521,12 @@ export function processNgTemplates(
         } else {
           template = template.replace(replaceRegex, t.children);
         }
-        // the +1 accounts for the t.count's counting of the original template
-        if (t.count === matches.length + 1 && safeToRemove) {
+
+        const dist = matches.filter(
+          (obj, index, self) => index === self.findIndex((t) => t.input === obj.input),
+        );
+
+        if ((t.count === dist.length || t.count - matches.length === 1) && safeToRemove) {
           const refsInComponentFile = getViewChildOrViewChildrenNames(sourceFile);
           if (refsInComponentFile?.length > 0) {
             const templateRefs = getTemplateReferences(template);

packages/core/schematics/test/control_flow_migration_spec.ts

@@ -6932,5 +6932,38 @@ describe('control flow migration', () => {
       const content = tree.readContent('/comp.ts');
       expect(content).not.toContain('<ng-template #contentTemplate>');
     });
+
+    it('should remove ng-template reference when use in if-else block', async () => {
+      writeFile(
+        '/comp.ts',
+        `
+        import {Component} from '@angular/core';
+
+        @Component({
+          templateUrl: './comp.html'
+        })
+        class Comp {
+        }
+      `,
+      );
+
+      writeFile(
+        '/comp.html',
+        [
+          `<div>`,
+          `<div *ngIf="param; else loading">`,
+          `<div>content</div>`,
+          `</div>`,
+          `<ng-template #loading>`,
+          `<div>loading</div>`,
+          `</ng-template>`,
+          `</div>`,
+        ].join('\n'),
+      );
+
+      await runMigration();
+      const content = tree.readContent('/comp.html');
+      expect(content).not.toContain('<ng-template #loading>');
+    });
   });
 });