addressed review comments

Author: mazyu36

packages/@aws-cdk/aws-amplify-alpha/lib/app.ts

@@ -6,7 +6,7 @@ import { CfnApp } from 'aws-cdk-lib/aws-amplify';
 import { BasicAuth } from './basic-auth';
 import { Branch, BranchOptions } from './branch';
 import { Domain, DomainOptions } from './domain';
-import { renderEnvironmentVariables } from './utils';
+import { renderEnvironmentVariables, isServerSideRendered } from './utils';
 import { addConstructMetadata, MethodMetadata } from 'aws-cdk-lib/core/lib/metadata-resource';
 import { propertyInjectable } from 'aws-cdk-lib/core/lib/prop-injectable';
 
@@ -20,11 +20,6 @@ export interface IApp extends IResource {
    * @attribute
    */
   readonly appId: string;
-
-  /**
-   * The platform of the app
-   */
-  readonly platform?: Platform;
 }
 
 /**
@@ -267,7 +262,7 @@ export class App extends Resource implements IApp, iam.IGrantable {
 
     let computedRole: iam.IRole | undefined;
     const appPlatform = props.platform || Platform.WEB;
-    const isSSR = appPlatform === Platform.WEB_COMPUTE || appPlatform === Platform.WEB_DYNAMIC;
+    const isSSR = isServerSideRendered(appPlatform);
 
     if (props.computeRole) {
       if (!isSSR) {

packages/@aws-cdk/aws-amplify-alpha/lib/branch.ts

@@ -14,9 +14,9 @@ import {
 import { Provider } from 'aws-cdk-lib/custom-resources';
 import { Construct } from 'constructs';
 import { CfnBranch } from 'aws-cdk-lib/aws-amplify';
-import { IApp, Platform } from './app';
+import { App, IApp, Platform } from './app';
 import { BasicAuth } from './basic-auth';
-import { renderEnvironmentVariables } from './utils';
+import { renderEnvironmentVariables, isServerSideRendered } from './utils';
 import { AssetDeploymentIsCompleteFunction, AssetDeploymentOnEventFunction } from '../custom-resource-handlers/dist/aws-amplify-alpha/asset-deployment-provider.generated';
 import { addConstructMetadata, MethodMetadata } from 'aws-cdk-lib/core/lib/metadata-resource';
 import { propertyInjectable } from 'aws-cdk-lib/core/lib/prop-injectable';
@@ -194,11 +194,13 @@ export class Branch extends Resource implements IBranch {
     // Enhanced CDK Analytics Telemetry
     addConstructMetadata(this, props);
 
-    const platform = props.app.platform;
-    const isSSR = platform === Platform.WEB_COMPUTE || platform === Platform.WEB_DYNAMIC;
+    if (props.app instanceof App) {
+      const platform = props.app.platform;
+      const isSSR = isServerSideRendered(platform);
 
-    if (props.computeRole && !isSSR) {
-      throw new ValidationError('`computeRole` can only be specified for branches of apps with `Platform.WEB_COMPUTE` or `Platform.WEB_DYNAMIC`.', this);
+      if (props.computeRole && !isSSR) {
+        throw new ValidationError('`computeRole` can only be specified for branches of apps with `Platform.WEB_COMPUTE` or `Platform.WEB_DYNAMIC`.', this);
+      }
     }
 
     this.environmentVariables = props.environmentVariables || {};

packages/@aws-cdk/aws-amplify-alpha/lib/utils.ts

@@ -1,3 +1,12 @@
+import { Platform } from './app';
+
 export function renderEnvironmentVariables(vars: { [name: string]: string }) {
   return Object.entries(vars).map(([name, value]) => ({ name, value }));
 }
+
+/**
+ * Utility function to check if the platform is a server-side rendering platform
+ */
+export function isServerSideRendered(platform?: Platform): boolean {
+  return platform === Platform.WEB_COMPUTE || platform === Platform.WEB_DYNAMIC;
+}