From 478e86fc63c438280da51ad200d8d969994346ba Mon Sep 17 00:00:00 2001
From: Alan Agius <alan.agius4@gmail.com>
Date: Fri, 28 May 2021 11:11:30 +0200
Subject: [PATCH] fix(@schematics/angular): make version 12 workspace config
 migration idempotent

With this change we ensure that `update-angular-config-v12` migration is idempotent

Closes #20979
---
 .../update-12/update-angular-config.ts          |  9 +++++++++
 .../update-12/update-angular-config_spec.ts     | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/packages/schematics/angular/migrations/update-12/update-angular-config.ts b/packages/schematics/angular/migrations/update-12/update-angular-config.ts
index 9589eb248490..ec32330418f3 100644
--- a/packages/schematics/angular/migrations/update-12/update-angular-config.ts
+++ b/packages/schematics/angular/migrations/update-12/update-angular-config.ts
@@ -59,6 +59,15 @@ function updateOptions(
   target: workspaces.TargetDefinition,
   optionsToUpdate: typeof ServerBuilderOptions | typeof BrowserBuilderOptions,
 ): void {
+  // This is a hacky way to make this migration idempotent.
+  // `defaultConfiguration` was only introduced in v12 projects and hence v11 projects do not have this property.
+  // Setting it as an empty string will not cause any side-effect.
+  if (typeof target.defaultConfiguration === 'string') {
+    return;
+  }
+
+  target.defaultConfiguration = '';
+
   if (!target.options) {
     target.options = {};
   }
diff --git a/packages/schematics/angular/migrations/update-12/update-angular-config_spec.ts b/packages/schematics/angular/migrations/update-12/update-angular-config_spec.ts
index 7f80e45ae5a8..0cabc91fa6b4 100644
--- a/packages/schematics/angular/migrations/update-12/update-angular-config_spec.ts
+++ b/packages/schematics/angular/migrations/update-12/update-angular-config_spec.ts
@@ -120,4 +120,21 @@ describe(`Migration to update 'angular.json'. ${schematicName}`, () => {
     expect(options.namedChunks).toBeTrue();
     expect(options.buildOptimizer).toBeFalse();
   });
+
+  it('migration should be idempotent', async () => {
+    const { options } = getBuildTarget(tree);
+    expect(options.aot).toBeTrue();
+
+    // First run
+    const newTree1 = await schematicRunner.runSchematicAsync(schematicName, {}, tree).toPromise();
+    const { options: options1 } = getBuildTarget(newTree1);
+    expect(options1.aot).toBeUndefined();
+
+    // Second run
+    const newTree2 = await schematicRunner
+      .runSchematicAsync(schematicName, {}, newTree1)
+      .toPromise();
+    const { options: options2 } = getBuildTarget(newTree2);
+    expect(options2.aot).toBeUndefined();
+  });
 });