feat(cloudfront): responseHttpStatus defaults to httpStatus in errorR…

…esponses (#11879)

Make `responseHttpStatus` default to `httpStatus` if `responsePagePath`
is defined.

This avoids repeating the error code and is more in line with the actual
`@default` documentation (which actually led me to think that it
already defaulted to `httpStatus`).


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-cloudfront/lib/distribution.ts

@@ -393,21 +393,18 @@ export class Distribution extends Resource implements IDistribution {
 
   private renderErrorResponses(): CfnDistribution.CustomErrorResponseProperty[] | undefined {
     if (this.errorResponses.length === 0) { return undefined; }
-    function validateCustomErrorResponse(errorResponse: ErrorResponse) {
-      if (errorResponse.responsePagePath && !errorResponse.responseHttpStatus) {
-        throw new Error('\'responseCode\' must be provided if \'responsePagePath\' is defined');
-      }
-      if (!errorResponse.responseHttpStatus && !errorResponse.ttl) {
-        throw new Error('A custom error response without either a \'responseCode\' or \'errorCachingMinTtl\' is not valid.');
-      }
-    }
-    this.errorResponses.forEach(e => validateCustomErrorResponse(e));
 
     return this.errorResponses.map(errorConfig => {
+      if (!errorConfig.responseHttpStatus && !errorConfig.ttl && !errorConfig.responsePagePath) {
+        throw new Error('A custom error response without either a \'responseHttpStatus\', \'ttl\' or \'responsePagePath\' is not valid.');
+      }
+
       return {
         errorCachingMinTtl: errorConfig.ttl?.toSeconds(),
         errorCode: errorConfig.httpStatus,
-        responseCode: errorConfig.responseHttpStatus,
+        responseCode: errorConfig.responsePagePath
+          ? errorConfig.responseHttpStatus ?? errorConfig.httpStatus
+          : errorConfig.responseHttpStatus,
         responsePagePath: errorConfig.responsePagePath,
       };
     });
@@ -577,7 +574,7 @@ export interface ErrorResponse {
    *
    * If you specify a value for `responseHttpStatus`, you must also specify a value for `responsePagePath`.
    *
-   * @default - not set, the error code will be returned as the response code.
+   * @default - the error code will be returned as the response code.
    */
   readonly responseHttpStatus?: number;
   /**

packages/@aws-cdk/aws-cloudfront/test/distribution.test.ts

@@ -318,20 +318,6 @@ describe('certificates', () => {
 
 describe('custom error responses', () => {
 
-  test('should fail if responsePagePath is defined but responseCode is not', () => {
-    const origin = defaultOrigin();
-
-    expect(() => {
-      new Distribution(stack, 'Dist', {
-        defaultBehavior: { origin },
-        errorResponses: [{
-          httpStatus: 404,
-          responsePagePath: '/errors/404.html',
-        }],
-      });
-    }).toThrow(/\'responseCode\' must be provided if \'responsePagePath\' is defined/);
-  });
-
   test('should fail if only the error code is provided', () => {
     const origin = defaultOrigin();
 
@@ -340,21 +326,28 @@ describe('custom error responses', () => {
         defaultBehavior: { origin },
         errorResponses: [{ httpStatus: 404 }],
       });
-    }).toThrow(/A custom error response without either a \'responseCode\' or \'errorCachingMinTtl\' is not valid./);
+    }).toThrow(/A custom error response without either a \'responseHttpStatus\', \'ttl\' or \'responsePagePath\' is not valid./);
   });
 
   test('should render the array of error configs if provided', () => {
     const origin = defaultOrigin();
     new Distribution(stack, 'Dist', {
       defaultBehavior: { origin },
       errorResponses: [{
+        // responseHttpStatus defaults to httpsStatus
         httpStatus: 404,
-        responseHttpStatus: 404,
         responsePagePath: '/errors/404.html',
       },
       {
+        // without responsePagePath
         httpStatus: 500,
         ttl: Duration.seconds(2),
+      },
+      {
+        // with responseHttpStatus different from httpStatus
+        httpStatus: 403,
+        responseHttpStatus: 200,
+        responsePagePath: '/index.html',
       }],
     });
 
@@ -370,6 +363,11 @@ describe('custom error responses', () => {
             ErrorCachingMinTTL: 2,
             ErrorCode: 500,
           },
+          {
+            ErrorCode: 403,
+            ResponseCode: 200,
+            ResponsePagePath: '/index.html',
+          },
         ],
       },
     });