fix(core): handle aliased index with no space in control flow migration (angular#52444)

The current regexp supposes that there is at least one space between the `=` and the aliased variable.
As it is possible to write `let myIndex=index`, this commit updates the regexp to handle such a case.

PR Close angular#52444

Author: cexbrayat

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

@@ -315,7 +315,7 @@ function buildIfThenElseBlock(
 }
 
 function migrateNgFor(etm: ElementToMigrate, tmpl: string, offset: number): Result {
-  const aliasWithEqualRegexp = /=\s+(count|index|first|last|even|odd)/gm;
+  const aliasWithEqualRegexp = /=\s*(count|index|first|last|even|odd)/gm;
   const aliasWithAsRegexp = /(count|index|first|last|even|odd)\s+as/gm;
   const aliases = [];
   const lbString = etm.hasLineBreaks ? lb : '';

packages/core/schematics/test/control_flow_migration_spec.ts

@@ -869,7 +869,6 @@ describe('control flow migration', () => {
           'template: `<ul>@for (itm of items; track trackMeFn($index, itm)) {<li>{{itm.text}}</li>}</ul>`');
     });
 
-
     it('should migrate with an index alias', async () => {
       writeFile('/comp.ts', `
         import {Component} from '@angular/core';
@@ -895,6 +894,31 @@ describe('control flow migration', () => {
           'template: `<ul>@for (itm of items; track itm; let index = $index) {<li>{{itm.text}}</li>}</ul>`');
     });
 
+    it('should migrate with an index alias with no spaces', async () => {
+      writeFile('/comp.ts', `
+        import {Component} from '@angular/core';
+        import {NgFor} from '@angular/common';
+        interface Item {
+          id: number;
+          text: string;
+        }
+
+        @Component({
+          imports: [NgFor],
+          template: \`<ul><li *ngFor="let itm of items; let index=index">{{itm.text}}</li></ul>\`
+        })
+        class Comp {
+          items: Item[] = [{id: 1, text: 'blah'},{id: 2, text: 'stuff'}];
+        }
+      `);
+
+      await runMigration();
+      const content = tree.readContent('/comp.ts');
+
+      expect(content).toContain(
+          'template: `<ul>@for (itm of items; track itm; let index = $index) {<li>{{itm.text}}</li>}</ul>`');
+    });
+
     it('should migrate with alias declared with as', async () => {
       writeFile('/comp.ts', `
         import {Component} from '@angular/core';