feat(neptune): change InstanceType to class that is built from string (…

…#14273)

closes #13923

BREAKING CHANGE: `InstanceType` changed from enum to enum-like static factory.

----

*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-neptune/lib/cluster.ts

@@ -503,7 +503,7 @@ export class DatabaseCluster extends DatabaseClusterBase implements IDatabaseClu
         dbClusterIdentifier: cluster.ref,
         dbInstanceIdentifier: instanceIdentifier,
         // Instance properties
-        dbInstanceClass: props.instanceType,
+        dbInstanceClass: props.instanceType._instanceType,
         dbParameterGroupName: props.parameterGroup?.parameterGroupName,
       });
 

packages/@aws-cdk/aws-neptune/lib/instance.ts

@@ -10,59 +10,92 @@ import { IParameterGroup } from './parameter-group';
  * Possible Instances Types to use in Neptune cluster
  * used for defining {@link DatabaseInstanceProps.instanceType}.
  */
-export enum InstanceType {
+export class InstanceType {
+
   /**
    * db.r5.large
    */
-  R5_LARGE = 'db.r5.large',
+  public static readonly R5_LARGE = InstanceType.of('db.r5.large');
+
   /**
    * db.r5.xlarge
    */
-  R5_XLARGE = 'db.r5.xlarge',
+  public static readonly R5_XLARGE = InstanceType.of('db.r5.xlarge');
+
   /**
    * db.r5.2xlarge
    */
-  R5_2XLARGE = 'db.r5.2xlarge',
+  public static readonly R5_2XLARGE = InstanceType.of('db.r5.2xlarge');
+
   /**
    * db.r5.4xlarge
    */
-  R5_4XLARGE = 'db.r5.4xlarge',
+  public static readonly R5_4XLARGE = InstanceType.of('db.r5.4xlarge');
+
   /**
    * db.r5.8xlarge
    */
-  R5_8XLARGE = 'db.r5.8xlarge',
+  public static readonly R5_8XLARGE = InstanceType.of('db.r5.8xlarge');
+
   /**
    * db.r5.12xlarge
    */
-  R5_12XLARGE = 'db.r5.12xlarge',
+  public static readonly R5_12XLARGE = InstanceType.of('db.r5.12xlarge');
+
   /**
    * db.r5.24xlarge
    */
-  R5_24XLARGE = 'db.r5.24xlarge',
+  public static readonly R5_24XLARGE = InstanceType.of('db.r5.24xlarge');
+
   /**
    * db.r4.large
    */
-  R4_LARGE = 'db.r4.large',
+  public static readonly R4_LARGE = InstanceType.of('db.r4.large');
+
   /**
    * db.r4.xlarge
    */
-  R4_XLARGE = 'db.r4.xlarge',
+  public static readonly R4_XLARGE = InstanceType.of('db.r4.xlarge');
+
   /**
    * db.r4.2xlarge
    */
-  R4_2XLARGE = 'db.r4.2xlarge',
+  public static readonly R4_2XLARGE = InstanceType.of('db.r4.2xlarge');
+
   /**
    * db.r4.4xlarge
    */
-  R4_4XLARGE = 'db.r4.4xlarge',
+  public static readonly R4_4XLARGE = InstanceType.of('db.r4.4xlarge');
+
   /**
    * db.r4.8xlarge
    */
-  R4_8XLARGE = 'db.r4.8xlarge',
+  public static readonly R4_8XLARGE = InstanceType.of('db.r4.8xlarge');
+
   /**
    * db.t3.medium
    */
-  T3_MEDIUM = 'db.t3.medium'
+  public static readonly T3_MEDIUM = InstanceType.of('db.t3.medium');
+
+  /**
+   * Build an InstanceType from given string or token, such as CfnParameter.
+   */
+  public static of(instanceType: string): InstanceType {
+    return new InstanceType(instanceType);
+  }
+
+  /**
+   * @internal
+   */
+  readonly _instanceType: string;
+
+  private constructor(instanceType: string) {
+    if (cdk.Token.isUnresolved(instanceType) || instanceType.startsWith('db.')) {
+      this._instanceType = instanceType;
+    } else {
+      throw new Error(`instance type must start with 'db.'; (got ${instanceType})`);
+    }
+  }
 }
 
 /**
@@ -212,7 +245,7 @@ export class DatabaseInstance extends cdk.Resource implements IDatabaseInstance
 
     const instance = new CfnDBInstance(this, 'Resource', {
       dbClusterIdentifier: props.cluster.clusterIdentifier,
-      dbInstanceClass: props.instanceType,
+      dbInstanceClass: props.instanceType._instanceType,
       availabilityZone: props.availabilityZone,
       dbInstanceIdentifier: props.dbInstanceName,
       dbParameterGroupName: props.parameterGroup?.parameterGroupName,

packages/@aws-cdk/aws-neptune/test/instance.test.ts

@@ -106,6 +106,40 @@ describe('DatabaseInstance', () => {
       DBParameterGroupName: { Ref: 'ParamsA8366201' },
     }));
   });
+
+  test('instance type from CfnParameter', () => {
+    // GIVEN
+    const stack = testStack();
+
+    const instanceType = new cdk.CfnParameter(stack, 'NeptuneInstaneType', {
+      description: 'Instance type of graph database Neptune',
+      type: 'String',
+      allowedValues: [
+        'db.r5.xlarge',
+        'db.r5.2xlarge',
+        'db.r5.4xlarge',
+        'db.r5.8xlarge',
+        'db.r5.12xlarge',
+      ],
+      default: 'db.r5.8xlarge',
+    });
+    // WHEN
+    new DatabaseInstance(stack, 'Instance', {
+      cluster: stack.cluster,
+      instanceType: InstanceType.of(instanceType.valueAsString),
+    });
+
+    // THEN
+    expectCDK(stack).to(haveResource('AWS::Neptune::DBInstance', {
+      DBInstanceClass: {
+        Ref: 'NeptuneInstaneType',
+      },
+    }));
+  });
+
+  test('instance type from string throws if missing db prefix', () => {
+    expect(() => { InstanceType.of('r5.xlarge');}).toThrowError(/instance type must start with 'db.'/);
+  });
 });
 
 class TestStack extends cdk.Stack {
@@ -128,4 +162,4 @@ class TestStack extends cdk.Stack {
 function testStack() {
   const stack = new TestStack(undefined, undefined, { env: { account: '12345', region: 'us-test-1' } });
   return stack;
-}
+}