feat(appsync): import existing graphql api

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

@@ -82,6 +82,24 @@ demoDS.createResolver({
 });
 ```
 
+## Imports
+
+Any GraphQL Api that has been created outside the stack can be imported from 
+another stack into your CDK app. Utilizing the `fromXxx` function, you have 
+the ability to add data sources and resolvers through a `IGraphQLApi` interface.
+
+```ts
+const importedApi = appsync.GraphQLApi.fromGraphQLApiAttributes(stack, 'IApi', {
+  graphqlApiId: api.apiId,
+  graphqlArn: api.arn,
+});
+importedApi.addDynamoDbDataSource('TableDataSource', 'Table', table);
+```
+
+If you don't specify `graphqlArn` in `fromXxxAttributes`, CDK will autogenerate
+the expected `arn` for the imported api, given the `apiId`. For creating data 
+sources and resolvers, an `apiId` is sufficient.
+
 ## Permissions
 
 When using `AWS_IAM` as the authorization type for GraphQL API, an IAM Role

packages/@aws-cdk/aws-appsync/lib/data-source.ts

@@ -3,7 +3,7 @@ import { IGrantable, IPrincipal, IRole, Role, ServicePrincipal } from '@aws-cdk/
 import { IFunction } from '@aws-cdk/aws-lambda';
 import { Construct, IResolvable } from '@aws-cdk/core';
 import { CfnDataSource } from './appsync.generated';
-import { GraphQLApi } from './graphqlapi';
+import { IGraphQLApi } from './graphqlapi-base';
 import { BaseResolverProps, Resolver } from './resolver';
 
 /**
@@ -13,7 +13,7 @@ export interface BaseDataSourceProps {
   /**
    * The API to attach this data source to
    */
-  readonly api: GraphQLApi;
+  readonly api: IGraphQLApi;
   /**
    * The name of the data source
    */
@@ -91,7 +91,7 @@ export abstract class BaseDataSource extends Construct {
    */
   public readonly ds: CfnDataSource;
 
-  protected api: GraphQLApi;
+  protected api: IGraphQLApi;
   protected serviceRole?: IRole;
 
   constructor(scope: Construct, id: string, props: BackedDataSourceProps, extended: ExtendedDataSourceProps) {

packages/@aws-cdk/aws-appsync/lib/graphqlapi-base.ts

@@ -0,0 +1,190 @@
+import { ITable } from '@aws-cdk/aws-dynamodb';
+import { IFunction } from '@aws-cdk/aws-lambda';
+import { CfnResource, IResource, Resource } from '@aws-cdk/core';
+import { DynamoDbDataSource, HttpDataSource, LambdaDataSource, NoneDataSource } from './data-source';
+
+/**
+ * Optional configuration for data sources
+ */
+export interface DataSourceOptions {
+  /**
+   * The name of the data source
+   *
+   * @default - Automatically generated name '<DataSourceType>CDKDataSource'
+   * i.e. (LambdaCDKDataSource)
+   */
+  readonly name?: string;
+
+  /**
+   * The description of the data source
+   *
+   * @default - No description
+   */
+  readonly description?: string;
+}
+
+/**
+ * Interface for GraphQL
+ */
+export interface IGraphQLApi extends IResource {
+
+  /**
+   * an unique AWS AppSync GraphQL API identifier
+   * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
+   *
+   * @attribute
+   */
+  readonly apiId: string;
+
+  /**
+   * the ARN of the API
+   *
+   * @attribute
+   */
+  readonly arn: string;
+
+  /**
+   * add a new dummy data source to this API. Useful for pipeline resolvers
+   * and for backend changes that don't require a data source.
+   *
+   * @param options The optional configuration for this data source
+   * @default name - 'NoneCDKDataSource'
+   * description - No description
+   */
+  addNoneDataSource(options?: DataSourceOptions): NoneDataSource;
+
+  /**
+   * add a new DynamoDB data source to this API
+   *
+   * @param table The DynamoDB table backing this data source
+   * @param options The optional configuration for this data source
+   * @default name - 'DynamoDbCDKDataSource'
+   * description - No description
+   */
+  addDynamoDbDataSource(table: ITable, options?: DataSourceOptions): DynamoDbDataSource;
+
+  /**
+   * add a new http data source to this API
+   *
+   * @param endpoint The http endpoint
+   * @param options The optional configuration for this data source
+   * @default name - 'HttpCDKDataSource'
+   * description - No description
+   */
+  addHttpDataSource(endpoint: string, options?: DataSourceOptions): HttpDataSource;
+
+  /**
+   * add a new Lambda data source to this API
+   *
+   * @param lambdaFunction The Lambda function to call to interact with this data source
+   * @param options The optional configuration for this data source
+   * @default name - 'LambdaCDKDataSource'
+   * description - No description
+   */
+  addLambdaDataSource(lambdaFunction: IFunction, options?: DataSourceOptions): LambdaDataSource;
+
+  /**
+   * Add schema dependency if not imported
+   *
+   * @param construct the dependee
+   */
+  addSchemaDependency(construct: CfnResource): boolean;
+}
+
+/**
+ * Base Class for GraphQL API
+ */
+export abstract class GraphQLApiBase extends Resource implements IGraphQLApi {
+
+  /**
+   * an unique AWS AppSync GraphQL API identifier
+   * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
+   */
+  public abstract readonly apiId: string;
+
+  /**
+   * the ARN of the API
+   */
+  public abstract readonly arn: string;
+
+  /**
+   * add a new none data source to this API. Useful for pipeline resolvers
+   * and for backend changes that don't require a data source.
+   *
+   * @param options The optional configuration for this data source
+   * @default name - 'NoneCDKDataSource'
+   * description - No description
+   */
+  public addNoneDataSource(options?: DataSourceOptions): NoneDataSource {
+    const name = options?.name ?? 'NoneCDKDataSource';
+    return new NoneDataSource(this, name, {
+      api: this,
+      name: name,
+      description: options?.description,
+    });
+  }
+
+  /**
+   * add a new DynamoDB data source to this API
+   *
+   * @param table The DynamoDB table backing this data source
+   * @param options The optional configuration for this data source
+   * @default name - 'DynamoDbCDKDataSource'
+   * description - No description
+   */
+  public addDynamoDbDataSource(table: ITable, options?: DataSourceOptions): DynamoDbDataSource {
+    const name = options?.name ?? 'DynamoDbCDKDataSource';
+    return new DynamoDbDataSource(this, name, {
+      api: this,
+      table,
+      name,
+      description: options?.description,
+    });
+  }
+
+  /**
+   * add a new http data source to this API
+   *
+   * @param endpoint The http endpoint
+   * @param options The optional configuration for this data source
+   * @default name - 'HttpCDKDataSource'
+   * description - No description
+   */
+  public addHttpDataSource(endpoint: string, options?: DataSourceOptions): HttpDataSource {
+    const name = options?.name ?? 'HttpCDKDataSource';
+    return new HttpDataSource(this, name, {
+      api: this,
+      endpoint,
+      name,
+      description: options?.description,
+    });
+  }
+
+  /**
+   * add a new Lambda data source to this API
+   *
+   * @param lambdaFunction The Lambda function to call to interact with this data source
+   * @param options The optional configuration for this data source
+   * @default name - 'LambdaCDKDataSource'
+   * description - No description
+   */
+  public addLambdaDataSource(lambdaFunction: IFunction, options?: DataSourceOptions): LambdaDataSource {
+    const name = options?.name ?? 'LambdaCDKDataSource';
+    return new LambdaDataSource(this, name, {
+      api: this,
+      lambdaFunction,
+      name,
+      description: options?.description,
+    });
+  }
+
+  /**
+   * Add schema dependency if not imported
+   *
+   * @param construct the dependee
+   */
+  public addSchemaDependency(construct: CfnResource): boolean {
+    construct;
+    return false;
+  }
+}