Add RetainExceptOnCreate removal policy

packages/aws-cdk-lib/core/lib/removal-policy.ts

@@ -48,6 +48,16 @@ export enum RemovalPolicy {
    * @see https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-attribute-deletionpolicy.html#aws-attribute-deletionpolicy-options
    */
   SNAPSHOT = 'snapshot',
+
+  /**
+   * RetainExceptOnCreate behaves like Retain for stack operations, except for the stack operation that initially created the resource.
+   * If the stack operation that created the resource is rolled back, CloudFormation deletes the resource. For all other stack operations,
+   * such as stack deletion, CloudFormation retains the resource and its contents. The result is that new, empty, and unused resources are deleted,
+   * while in-use resources and their data are retained.
+   *
+   * @see https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-attribute-deletionpolicy.html#aws-attribute-deletionpolicy-options
+   */
+  RETAIN_EXCEPT_ON_CREATE = 'RetainExceptOnCreate',
 }
 
 export interface RemovalPolicyOptions {

packages/aws-cdk-lib/core/test/removal-policy.test.ts

@@ -0,0 +1,32 @@
+import { toCloudFormation } from './util';
+import { CfnResource, Stack, RemovalPolicy } from '../lib';
+
+describe('removal policy', () => {
+  const removalPolicies = [
+    RemovalPolicy.RETAIN,
+    RemovalPolicy.DESTROY,
+    RemovalPolicy.SNAPSHOT,
+    RemovalPolicy.RETAIN_EXCEPT_ON_CREATE,
+  ];
+  removalPolicies.forEach((policy) => {
+    test(`should handle RemovalPolicy.${policy}`, () => {
+      const stack = new Stack();
+
+      new CfnResource(stack, 'Resource', {
+        type: 'MOCK',
+        properties: {
+          RemovalPolicy: policy,
+        },
+      });
+
+      expect(toCloudFormation(stack)).toEqual({
+        Resources: {
+          Resource: {
+            Type: 'MOCK',
+            Properties: { RemovalPolicy: policy.valueOf() },
+          },
+        },
+      });
+    });
+  });
+});