feat(aws-apigateway): API Gateway Construct Library (#665)

Introduce an initial construct library for API Gateway. By all means it does not cover 
the entire surface area of API Gateway, but provides basic support for defining 
API gateway configurations (resources/methods hierarchy).

Integration support includes `LambdaIntegration` which accepts a `lambda.Function`, 
sets up the appropriate permissions and binds it to an API method.

Includes many "smart defaults" at every level such as:

- Automatically define a `Deployment` and a `Stage` for the API, which will be recreated every time the API configuration changes (by generating the logical ID of the AWS::ApiGateway::Deployment resource from a hash of the API configuration, similarly to SAM).
- Automatically configure a role for API Gateway to allow writing CloudWatch logs and alarms.
- Specify `defaultIntegration` at the API level which will apply to all methods without integration.

Supports defining APIs like this:

```ts
const integ = new apigw.LambdaIntegration(toysLambdaHandler);
const api = new apigw.RestApi(this, 'my-awesome-api');

api.root.onMethod('GET', new apigw.HttpIntegration('https://amazon.com/toys'));

const toys = api.root.addResource('toys', { defaultIntegration: integ });
toys.addMethod('ANY');

const toy = toys.addResource('{toy}');
toy.addMethod('GET'); // get a toy
toy.addMethod('DELETE'); // remove a toy
```

See [README] for more details.

[README]: https://github.com/awslabs/aws-cdk/blob/c99e7285e7b24700cfd4d52f6da32cffe12c511c/packages/%40aws-cdk/aws-apigateway/README.md

### Framework Changes

 * __resolve__: allow object keys to include tokens, as long as they resolvable to strings.
 * __assert__: invoke `stack.validateTree()` by default for `expect(stack)` to simulate synthesis.

----

* Features not supported yet are listed here: #727, #723
* Fixes #602, copy: @hassankhan

packages/@aws-cdk/assert/lib/expect.ts

@@ -2,14 +2,27 @@ import cdk = require('@aws-cdk/cdk');
 import api = require('@aws-cdk/cx-api');
 import { StackInspector } from './inspector';
 
-export function expect(stack: api.SynthesizedStack | cdk.Stack): StackInspector {
+export function expect(stack: api.SynthesizedStack | cdk.Stack, skipValidation = false): StackInspector {
     // Can't use 'instanceof' here, that breaks if we have multiple copies
     // of this library.
-    const sstack: api.SynthesizedStack = isStackClassInstance(stack) ? {
-        name: 'test',
-        template: stack.toCloudFormation(),
-        metadata: {}
-    } : stack;
+    let sstack: api.SynthesizedStack;
+
+    if (isStackClassInstance(stack)) {
+        if (!skipValidation) {
+            const errors = stack.validateTree();
+            if (errors.length > 0) {
+                throw new Error(`Stack validation failed:\n${errors.map(e => `${e.message} at: ${e.source.parent}`).join('\n')}`);
+            }
+        }
+
+        sstack = {
+            name: 'test',
+            template: stack.toCloudFormation(),
+            metadata: {}
+        };
+    } else {
+        sstack = stack;
+    }
 
     return new StackInspector(sstack);
 }

packages/@aws-cdk/aws-apigateway/README.md

@@ -1,2 +1,165 @@
-## The CDK Construct Library for AWS API Gateway
-This module is part of the [AWS Cloud Development Kit](https://github.com/awslabs/aws-cdk) project.
+## CDK Construct Library for Amazon API Gateway
+
+Amazon API Gateway is a fully managed service that makes it easy for developers
+to publish, maintain, monitor, and secure APIs at any scale. Create an API to
+access data, business logic, or functionality from your back-end services, such
+as applications running on Amazon Elastic Compute Cloud (Amazon EC2), code
+running on AWS Lambda, or any web application.
+
+### Defining APIs
+
+APIs are defined as a hierarchy of resources and methods. `addResource` and
+`addMethod` can be used to build this hierarchy. The root resource is
+`api.root`.
+
+For example, the following code defines an API that includes the following HTTP
+endpoints: `ANY /, GET /books`, `POST /books`, `GET /books/{book_id}`, `DELETE /books/{book_id}`.
+
+```ts
+const api = new apigateway.RestApi(this, 'books-api');
+
+api.root.addMethod('ANY');
+
+const books = api.root.addResource('books');
+books.addMethod('GET');
+books.addMethod('POST');
+
+const book = books.addResource('{book_id}');
+book.addMethod('GET');
+book.addMethod('DELETE');
+```
+
+### Integration Targets
+
+Methods are associated with backend integrations, which are invoked when this
+method is called. API Gateway supports the following integrations:
+
+ * `MockIntegration` - can be used to test APIs. This is the default
+   integration if one is not specified.
+ * `LambdaIntegration` - can be used to invoke an AWS Lambda function.
+ * `AwsIntegration` - can be used to invoke arbitrary AWS service APIs.
+ * `HttpIntegration` - can be used to invoke HTTP endpoints.
+
+The following example shows how to integrate the `GET /book/{book_id}` method to
+an AWS Lambda function:
+
+```ts
+const getBookHandler = new lambda.Function(...);
+const getBookIntegration = new apigateway.LambdaIntegration(getBookHandler);
+book.addMethod('GET', getBookIntegration);
+```
+
+Integration options can be optionally be specified:
+
+```ts
+const getBookIntegration = new apigateway.LambdaIntegration(getBookHandler, {
+  contentHandling: apigateway.ContentHandling.ConvertToText, // convert to base64
+  credentialsPassthrough: true, // use caller identity to invoke the function
+});
+```
+
+Method options can optionally be specified when adding methods:
+
+```ts
+book.addMethod('GET', getBookIntegration, {
+  authorizationType: apigateway.AuthorizationType.IAM,
+  apiKeyRequired: true
+});
+```
+
+#### Default Integration and Method Options
+
+The `defaultIntegration` and `defaultMethodOptions` properties can be used to
+configure a default integration at any resource level. These options will be
+used when defining method under this resource (recursively) with undefined
+integration or options.
+
+> If not defined, the default integration is `MockIntegration`. See reference
+documentation for default method options.
+
+The following example defines the `booksBackend` integration as a default
+integration. This means that all API methods that do not explicitly define an
+integration will be routed to this AWS Lambda function.
+
+```ts
+const booksBackend = new apigateway.LambdaIntegration(...);
+const api = new apigateway.RestApi(this, 'books', {
+  defaultIntegration: booksBackend
+});
+
+const books = new api.root.addResource('books');
+books.addMethod('GET');  // integrated with `booksBackend`
+books.addMethod('POST'); // integrated with `booksBackend`
+
+const book = books.addResource('{book_id}');
+book.addMethod('GET');   // integrated with `booksBackend`
+```
+
+### Deployments
+
+By default, the `RestApi` construct will automatically create an API Gateway
+[Deployment] and a "prod" [Stage] which represent the API configuration you
+defined in your CDK app. This means that when you deploy your app, your API will
+be have open access from the internet via the stage URL.
+
+The URL of your API can be obtained from the attribute `restApi.url`, and is
+also exported as an `Output` from your stack, so it's printed when you `cdk
+deploy` your app:
+
+```
+$ cdk deploy
+...
+books.booksapiEndpointE230E8D5 = https://6lyktd4lpk.execute-api.us-east-1.amazonaws.com/prod/
+```
+
+To disable this behavior, you can set `{ deploy: false }` when creating your
+API. This means that the API will not be deployed and a stage will not be
+created for it. You will need to manually define a `apigateway.Deployment` and
+`apigateway.Stage` resources.
+
+Use the `deployOptions` property to customize the deployment options of your
+API.
+
+The following example will configure API Gateway to emit logs and data traces to
+AWS CloudWatch for all API calls:
+
+> By default, an IAM role will be created and associated with API Gateway to
+allow it to write logs and metrics to AWS CloudWatch `cloudWatchRole` is set to
+`false`.
+
+```ts
+const api = new apigateway.RestApi(this, 'books', {
+  deployOptions: {
+    loggingLevel: apigateway.MethodLoggingLevel.Info,
+    dataTraceEnabled: true
+  }
+})
+```
+
+#### Deeper dive: invalidation of deployments
+
+API Gateway deployments are an immutable snapshot of the API. This means that we
+want to automatically create a new deployment resource every time the API model
+defined in our CDK app changes.
+
+In order to achieve that, the AWS CloudFormation logical ID of the
+`AWS::ApiGateway::Deployment` resource is dynamically calculated by hashing the
+API configuration (resources, methods). This means that when the configuration
+changes (i.e. a resource or method are added, configuration is changed), a new
+logical ID will be assigned to the deployment resource. This will cause
+CloudFormation to create a new deployment resource.
+
+By default, old deployments are _deleted_. You can set `retainDeployments: true`
+to allow users revert the stage to an old deployment manually.
+
+[Deployment]: https://docs.aws.amazon.com/apigateway/api-reference/resource/deployment/
+[Stage]: https://docs.aws.amazon.com/apigateway/api-reference/resource/stage/
+
+### Missing Features
+
+See [awslabs/aws-cdk#723](https://github.com/awslabs/aws-cdk/issues/723) for a
+list of missing features.
+
+----
+
+This module is part of the [AWS Cloud Development Kit](https://github.com/awslabs/aws-cdk) project.