From a6827b8e4989c64cd4439e733561c910af72007f Mon Sep 17 00:00:00 2001
From: Jamie Lynch <jamie.lynch@guardian.co.uk>
Date: Thu, 28 Jan 2021 14:14:10 +0000
Subject: [PATCH] take an instanceType prop or default to new param

---
 src/constructs/autoscaling/asg.test.ts | 18 ++++++++++++++++--
 src/constructs/autoscaling/asg.ts      |  5 ++---
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/constructs/autoscaling/asg.test.ts b/src/constructs/autoscaling/asg.test.ts
index 94beb24d19..cfbf7b2967 100644
--- a/src/constructs/autoscaling/asg.test.ts
+++ b/src/constructs/autoscaling/asg.test.ts
@@ -1,6 +1,6 @@
 import "@aws-cdk/assert/jest";
 import { SynthUtils } from "@aws-cdk/assert/lib/synth-utils";
-import { Vpc } from "@aws-cdk/aws-ec2";
+import { InstanceType, Vpc } from "@aws-cdk/aws-ec2";
 import { ApplicationProtocol } from "@aws-cdk/aws-elasticloadbalancingv2";
 import { Stack } from "@aws-cdk/core";
 import { simpleGuStackForTesting } from "../../../test/utils/simple-gu-stack";
@@ -40,7 +40,7 @@ describe("The GuAutoScalingGroup", () => {
     });
   });
 
-  test("adds the instanceType parameter", () => {
+  test("adds the instanceType parameter if none provided", () => {
     const stack = simpleGuStackForTesting();
 
     new GuAutoScalingGroup(stack, "AutoscalingGroup", defaultProps);
@@ -60,6 +60,20 @@ describe("The GuAutoScalingGroup", () => {
     });
   });
 
+  test("does not create the instanceType parameter if value is provided", () => {
+    const stack = simpleGuStackForTesting();
+
+    new GuAutoScalingGroup(stack, "AutoscalingGroup", { ...defaultProps, instanceType: new InstanceType("t3.small") });
+
+    const json = SynthUtils.toCloudFormation(stack) as SynthedStack;
+
+    expect(Object.keys(json.Parameters)).not.toContain(InstanceType);
+
+    expect(stack).toHaveResource("AWS::AutoScaling::LaunchConfiguration", {
+      InstanceType: "t3.small",
+    });
+  });
+
   test("correctly sets the user data using prop", () => {
     const stack = simpleGuStackForTesting();
 
diff --git a/src/constructs/autoscaling/asg.ts b/src/constructs/autoscaling/asg.ts
index 65e791b0ba..5c8fde85c3 100644
--- a/src/constructs/autoscaling/asg.ts
+++ b/src/constructs/autoscaling/asg.ts
@@ -11,6 +11,7 @@ import { GuAmiParameter, GuInstanceTypeParameter } from "../core";
 // https://www.typescriptlang.org/docs/handbook/utility-types.html#omittype-keys
 export interface GuAutoScalingGroupProps
   extends Omit<AutoScalingGroupProps, "imageId" | "osType" | "machineImage" | "instanceType" | "userData"> {
+  instanceType?: InstanceType;
   osType?: OperatingSystemType;
   machineImage?: MachineImage;
   userData: string;
@@ -25,8 +26,6 @@ export class GuAutoScalingGroup extends AutoScalingGroup {
       description: "AMI ID",
     });
 
-    const instanceType = new GuInstanceTypeParameter(scope);
-
     // We need to override getImage() so that we can pass in the AMI as a parameter
     // Otherwise, MachineImage.lookup({ name: 'some str' }) would work as long
     // as the name is hard-coded
@@ -41,7 +40,7 @@ export class GuAutoScalingGroup extends AutoScalingGroup {
     const mergedProps = {
       ...props,
       machineImage: { getImage: getImage },
-      instanceType: new InstanceType(instanceType.valueAsString),
+      instanceType: props.instanceType ?? new InstanceType(new GuInstanceTypeParameter(scope).valueAsString),
       userData: UserData.custom(props.userData),
     };