fix(@schematics/angular): preserve workspace build version

Author: raashish1601

packages/schematics/angular/migrations/use-application-builder/migration.ts

@@ -15,6 +15,7 @@ import {
   externalSchematic,
 } from '@angular-devkit/schematics';
 import { dirname, join } from 'node:path/posix';
+import { getPackageJsonDependency } from '../../utility/dependencies';
 import {
   DependencyType,
   ExistingBehavior,
@@ -270,8 +271,11 @@ function updateProjects(tree: Tree, context: SchematicContext) {
       }
 
       // Add direct @angular/build dependencies and remove @angular-devkit/build-angular
+      const buildDependency =
+        getPackageJsonDependency(tree, '@angular-devkit/build-angular') ??
+        getPackageJsonDependency(tree, '@angular/build');
       rules.push(
-        addDependency('@angular/build', latestVersions.DevkitBuildAngular, {
+        addDependency('@angular/build', buildDependency?.version ?? latestVersions.AngularBuild, {
           type: DependencyType.Dev,
           existing: ExistingBehavior.Replace,
         }),

packages/schematics/angular/migrations/use-application-builder/migration_spec.ts

@@ -450,6 +450,23 @@ describe(`Migration to use the application builder`, () => {
     expect(devDependencies['postcss']).toBeUndefined();
   });
 
+  it('should reuse the installed builder version when migrating to "@angular/build"', async () => {
+    tree.overwrite(
+      '/package.json',
+      JSON.stringify({
+        devDependencies: {
+          '@angular-devkit/build-angular': '~18.2.20',
+        },
+      }),
+    );
+
+    const newTree = await schematicRunner.runSchematic(schematicName, {}, tree);
+
+    const { devDependencies } = JSON.parse(newTree.readContent('/package.json'));
+    expect(devDependencies['@angular/build']).toBe('~18.2.20');
+    expect(devDependencies['@angular-devkit/build-angular']).toBeUndefined();
+  });
+
   it('it should not add esModuleInterop and moduleResolution when module is preserve', async () => {
     tree.overwrite(
       'tsconfig.json',