feat(pipelines): revised version of the API

packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts

@@ -479,7 +479,7 @@ export class Pipeline extends PipelineBase {
   }
 
   /** @internal */
-  public _attachActionToPipeline(stage: Stage, action: IAction, actionScope: CoreConstruct): FullActionDescriptor {
+  public _attachActionToPipeline(stage: Stage, action: IAction, actionScope: Construct): FullActionDescriptor {
     const richAction = new RichAction(action, this);
 
     // handle cross-region actions here
@@ -491,8 +491,8 @@ export class Pipeline extends PipelineBase {
     // // CodePipeline Variables
     validateNamespaceName(richAction.actionProperties.variablesNamespace);
 
-    // bind the Action
-    const actionConfig = richAction.bind(actionScope, stage, {
+    // bind the Action (type h4x)
+    const actionConfig = richAction.bind(actionScope as CoreConstruct, stage, {
       role: actionRole ? actionRole : this.role,
       bucket: crossRegionInfo.artifactBucket,
     });

packages/@aws-cdk/aws-codepipeline/lib/private/stage.ts

@@ -1,5 +1,6 @@
 import * as events from '@aws-cdk/aws-events';
 import * as cdk from '@aws-cdk/core';
+import { Construct, Node } from 'constructs';
 import { IAction, IPipeline, IStage } from '../action';
 import { Artifact } from '../artifact';
 import { CfnPipeline } from '../codepipeline.generated';
@@ -137,7 +138,15 @@ export class Stage implements IStage {
 
   private attachActionToPipeline(action: IAction): FullActionDescriptor {
     // notify the Pipeline of the new Action
-    const actionScope = new cdk.Construct(this.scope, action.actionProperties.actionName);
+    //
+    // It may be that a construct already exists with the given action name (CDK Pipelines
+    // may do this to maintain construct tree compatibility between versions).
+    //
+    // If so, we simply reuse it.
+    let actionScope = Node.of(this.scope).tryFindChild(action.actionProperties.actionName) as Construct | undefined;
+    if (!actionScope) {
+      actionScope = new cdk.Construct(this.scope, action.actionProperties.actionName);
+    }
     return this._pipeline._attachActionToPipeline(this, action, actionScope);
   }