fix(lambda): unable to access SingletonFunction vpc connections

packages/@aws-cdk/aws-lambda/lib/singleton-lambda.ts

@@ -1,3 +1,4 @@
+import * as ec2 from '@aws-cdk/aws-ec2';
 import * as iam from '@aws-cdk/aws-iam';
 import * as cdk from '@aws-cdk/core';
 import { Construct } from 'constructs';
@@ -63,6 +64,20 @@ export class SingletonFunction extends FunctionBase {
     this.canCreatePermissions = true; // Doesn't matter, addPermission is overriden anyway
   }
 
+  /**
+   * @inheritdoc
+   */
+  public get isBoundToVpc(): boolean {
+    return this.lambdaFunction.isBoundToVpc;
+  }
+
+  /**
+   * @inheritdoc
+   */
+  public get connections(): ec2.Connections {
+    return this.lambdaFunction.connections;
+  }
+
   /**
    * Returns a `lambda.Version` which represents the current version of this
    * singleton Lambda function. A new version will be created every time the

packages/@aws-cdk/aws-lambda/test/singleton-lambda.test.ts

@@ -1,5 +1,6 @@
 import '@aws-cdk/assert-internal/jest';
 import { ResourcePart } from '@aws-cdk/assert-internal';
+import * as ec2 from '@aws-cdk/aws-ec2';
 import * as iam from '@aws-cdk/aws-iam';
 import * as cdk from '@aws-cdk/core';
 import * as lambda from '../lib';
@@ -174,4 +175,27 @@ describe('singleton lambda', () => {
       },
     });
   });
+
+  test('bind to vpc and access connections', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'VPC', { maxAzs: 2 });
+    const securityGroup = new ec2.SecurityGroup(stack, 'SecurityGroup', {
+      vpc: vpc,
+    });
+
+    // WHEN
+    const singleton = new lambda.SingletonFunction(stack, 'Singleton', {
+      uuid: '84c0de93-353f-4217-9b0b-45b6c993251a',
+      code: new lambda.InlineCode('foo'),
+      runtime: lambda.Runtime.NODEJS_12_X,
+      handler: 'index.handler',
+      securityGroups: [securityGroup],
+      vpc: vpc,
+    });
+
+    // THEN
+    expect(singleton.isBoundToVpc).toBeTruthy();
+    expect(singleton.connections).toEqual(new ec2.Connections({ securityGroups: [securityGroup] }));
+  });
 });