fix(apigateway): unable to enable cors with a root proxy and LambdaRe…

…stApi (#5249)

If a proxy resource is added to the root, it will reflect any `addMethod` calls to the root resource, which causes two OPTIONS methods to be created when CORS is specified (one directly against the root resource and one by the proxy).

This uncovered a more general bug where if the proxy resource was added to the root, and the root already included a method of a certain kind, we will get a duplicate.

The fix is to avoid the proxy `addMethod` reflection on the root in case there is already a method by that type on the root.

This, indirectly, also fixes #5232, where CORS cannot be used with `LambdaRestApi`, which is basically a root proxy.

packages/@aws-cdk/aws-apigateway/lib/resource.ts

@@ -462,7 +462,10 @@ export class ProxyResource extends Resource {
     // In case this proxy is mounted under the root, also add this method to
     // the root so that empty paths are proxied as well.
     if (this.parentResource && this.parentResource.path === '/') {
-      this.parentResource.addMethod(httpMethod, integration, options);
+      // skip if the root resource already has this method defined
+      if (!(this.parentResource.node.tryFindChild(httpMethod) instanceof Method)) {
+        this.parentResource.addMethod(httpMethod, integration, options);
+      }
     }
     return super.addMethod(httpMethod, integration, options);
   }

packages/@aws-cdk/aws-apigateway/test/test.cors.ts

@@ -1,4 +1,5 @@
 import { countResources, expect, haveResource } from '@aws-cdk/assert';
+import lambda = require('@aws-cdk/aws-lambda');
 import { Duration, Stack } from '@aws-cdk/core';
 import { Test } from 'nodeunit';
 import apigw = require('../lib');
@@ -645,6 +646,62 @@ export = {
       }
     }), /Invalid "allowOrigins" - cannot mix "\*" with specific origins: https:\/\/bla\.com,\*,https:\/\/specific/);
 
+    test.done();
+  },
+
+  'defaultCorsPreflightOptions can be used to specify CORS for all resource tree [LambdaRestApi]'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+
+    const handler = new lambda.Function(stack, 'handler', {
+      handler: 'index.handler',
+      code: lambda.Code.fromInline('boom'),
+      runtime: lambda.Runtime.NODEJS_10_X,
+    });
+
+    // WHEN
+    new apigw.LambdaRestApi(stack, 'lambda-rest-api', {
+      handler,
+      defaultCorsPreflightOptions: {
+        allowOrigins: ['https://amazon.com'],
+      }
+    });
+
+    // THEN
+    expect(stack).to(countResources('AWS::ApiGateway::Method', 4)); // two ANY and two OPTIONS resources
+    expect(stack).to(haveResource('AWS::ApiGateway::Method', {
+      HttpMethod: 'OPTIONS',
+      ResourceId: {
+        "Fn::GetAtt": [
+          "lambdarestapiAAD10924",
+          "RootResourceId"
+        ]
+      },
+    }));
+    expect(stack).to(haveResource('AWS::ApiGateway::Method', {
+      HttpMethod: 'OPTIONS',
+      ResourceId: {
+        Ref: "lambdarestapiproxyE3AE07E3"
+      }
+    }));
+    test.done();
+  },
+
+  'CORS and proxy resources'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+
+    // WHEN
+    const api = new apigw.RestApi(stack, 'API', {
+      defaultCorsPreflightOptions: { allowOrigins: [ '*' ] }
+    });
+
+    api.root.addProxy();
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ApiGateway::Method', {
+      HttpMethod: 'OPTIONS',
+    }));
     test.done();
   }
-};
+};

packages/@aws-cdk/aws-apigateway/test/test.lambda-api.ts

@@ -199,4 +199,60 @@ export = {
 
     test.done();
   },
+
+  'LambdaRestApi defines a REST API with CORS enabled'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+
+    const handler = new lambda.Function(stack, 'handler', {
+      handler: 'index.handler',
+      code: lambda.Code.fromInline('boom'),
+      runtime: lambda.Runtime.NODEJS_10_X,
+    });
+
+    // WHEN
+    new apigw.LambdaRestApi(stack, 'lambda-rest-api', {
+      handler,
+      defaultCorsPreflightOptions: {
+        allowOrigins: ['https://aws.amazon.com'],
+        allowMethods: ['GET', 'PUT']
+      }
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ApiGateway::Method', {
+      HttpMethod: 'OPTIONS',
+      ResourceId: { Ref: 'lambdarestapiproxyE3AE07E3' },
+      Integration: {
+        IntegrationResponses: [
+          {
+            ResponseParameters: {
+              "method.response.header.Access-Control-Allow-Headers": "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token,X-Amz-User-Agent'",
+              "method.response.header.Access-Control-Allow-Origin": "'https://aws.amazon.com'",
+              "method.response.header.Vary": "'Origin'",
+              "method.response.header.Access-Control-Allow-Methods": "'GET,PUT'",
+            },
+            StatusCode: "204"
+          }
+        ],
+        RequestTemplates: {
+          "application/json": "{ statusCode: 200 }"
+        },
+        Type: "MOCK"
+      },
+      MethodResponses: [
+        {
+          ResponseParameters: {
+            "method.response.header.Access-Control-Allow-Headers": true,
+            "method.response.header.Access-Control-Allow-Origin": true,
+            "method.response.header.Vary": true,
+            "method.response.header.Access-Control-Allow-Methods": true,
+          },
+          StatusCode: "204"
+        }
+      ]
+    }));
+
+    test.done();
+  }
 };

packages/@aws-cdk/aws-apigateway/test/test.resource.ts

@@ -178,6 +178,20 @@ export = {
     test.done();
   },
 
+  'if proxy is added to root, proxy methods are only added if they are not defined already on the root resource'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+    const api = new apigw.RestApi(stack, 'api');
+    api.root.addMethod('POST');
+    const proxy = api.root.addProxy({ anyMethod: false });
+
+    // WHEN
+    proxy.addMethod('POST');
+
+    // THEN
+    test.done();
+  },
+
   'url for a resource'(test: Test) {
     // GIVEN
     const stack = new Stack();