fix(appsync): resolver unable to set pipelineConfig (#9093)

**[ISSUE]**
`pipelineConfig` was be labeled as `undefined` while using the `Resolver` class instead of `createResolver`. Also, no way to set `kind` parameter for resolvers, so implemented that as well.

**[APPROACH]**
Created a property that takes `pipelineConfig` for `AppSync` functions. 

**[NOTE]**
`pipelineConfig` takes a string array for the name of `AppSync Functions` not `Lambda Functions`

Fixes #6923  

BREAKING CHANGE: `pipelineConfig` is now an array of `string` instead of `CfnResolver.PipelineConfigProperty` for usability.
- **appsync**: `pipelineConfig` parameter takes in `string []`

----

*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-appsync/lib/resolver.ts

@@ -1,8 +1,9 @@
-import { Construct, IResolvable } from '@aws-cdk/core';
+import { Construct } from '@aws-cdk/core';
 import { CfnResolver } from './appsync.generated';
 import { BaseDataSource } from './data-source';
 import { GraphQLApi } from './graphqlapi';
 import { MappingTemplate } from './mapping-template';
+
 /**
  * Basic properties for an AppSync resolver
  */
@@ -18,9 +19,10 @@ export interface BaseResolverProps {
   /**
    * configuration of the pipeline resolver
    *
-   * @default - create a UNIT resolver
+   * @default - no pipeline resolver configuration
+   * An empty array | undefined sets resolver to be of kind, unit
    */
-  readonly pipelineConfig?: CfnResolver.PipelineConfigProperty | IResolvable;
+  readonly pipelineConfig?: string[];
   /**
    * The request mapping template for this resolver
    *
@@ -65,12 +67,15 @@ export class Resolver extends Construct {
   constructor(scope: Construct, id: string, props: ResolverProps) {
     super(scope, id);
 
+    const pipelineConfig = props.pipelineConfig && props.pipelineConfig.length ? { functions: props.pipelineConfig } : undefined;
+
     this.resolver = new CfnResolver(this, 'Resource', {
       apiId: props.api.apiId,
       typeName: props.typeName,
       fieldName: props.fieldName,
       dataSourceName: props.dataSource ? props.dataSource.name : undefined,
-      kind: props.pipelineConfig ? 'PIPELINE' : 'UNIT',
+      kind: pipelineConfig ? 'PIPELINE' : 'UNIT',
+      pipelineConfig: pipelineConfig,
       requestMappingTemplate: props.requestMappingTemplate ? props.requestMappingTemplate.renderTemplate() : undefined,
       responseMappingTemplate: props.responseMappingTemplate ? props.responseMappingTemplate.renderTemplate() : undefined,
     });

packages/@aws-cdk/aws-appsync/test/appsync.test.ts

@@ -4,10 +4,10 @@ import * as cdk from '@aws-cdk/core';
 import * as appsync from '../lib';
 
 test('should not throw an Error', () => {
-  // Given
+  // GIVEN
   const stack = new cdk.Stack();
 
-  // When
+  // WHEN
   const when = () => {
     new appsync.GraphQLApi(stack, 'api', {
       authorizationConfig: {},
@@ -16,6 +16,78 @@ test('should not throw an Error', () => {
     });
   };
 
-  // Then
+  // THEN
   expect(when).not.toThrow();
 });
+
+test('appsync should configure pipeline when pipelineConfig has contents', () => {
+  // GIVEN
+  const stack = new cdk.Stack();
+
+  // WHEN
+  const api = new appsync.GraphQLApi(stack, 'api', {
+    authorizationConfig: {},
+    name: 'api',
+    schemaDefinitionFile: path.join(__dirname, 'appsync.test.graphql'),
+  });
+
+  new appsync.Resolver(stack, 'resolver', {
+    api: api,
+    typeName: 'test',
+    fieldName: 'test2',
+    pipelineConfig: ['test', 'test'],
+  });
+
+  // THEN
+  expect(stack).toHaveResourceLike('AWS::AppSync::Resolver', {
+    Kind: 'PIPELINE',
+    PipelineConfig: { Functions: [ 'test', 'test' ] },
+  });
+});
+
+test('appsync should configure resolver as unit when pipelineConfig is empty', () => {
+  // GIVEN
+  const stack = new cdk.Stack();
+
+  // WHEN
+  const api = new appsync.GraphQLApi(stack, 'api', {
+    authorizationConfig: {},
+    name: 'api',
+    schemaDefinitionFile: path.join(__dirname, 'appsync.test.graphql'),
+  });
+
+  new appsync.Resolver(stack, 'resolver', {
+    api: api,
+    typeName: 'test',
+    fieldName: 'test2',
+  });
+
+  // THEN
+  expect(stack).toHaveResourceLike('AWS::AppSync::Resolver', {
+    Kind: 'UNIT',
+  });
+});
+
+test('appsync should configure resolver as unit when pipelineConfig is empty array', () => {
+  // GIVEN
+  const stack = new cdk.Stack();
+
+  // WHEN
+  const api = new appsync.GraphQLApi(stack, 'api', {
+    authorizationConfig: {},
+    name: 'api',
+    schemaDefinitionFile: path.join(__dirname, 'appsync.test.graphql'),
+  });
+
+  new appsync.Resolver(stack, 'resolver', {
+    api: api,
+    typeName: 'test',
+    fieldName: 'test2',
+    pipelineConfig: [],
+  });
+
+  // THEN
+  expect(stack).toHaveResourceLike('AWS::AppSync::Resolver', {
+    Kind: 'UNIT',
+  });
+});