fix(pipelines): "Node with duplicate id" on duplicate stack names

packages/aws-cdk-lib/pipelines/lib/helpers-internal/graph.ts

@@ -230,6 +230,10 @@ export class Graph<A> extends GraphNode<A> {
     return this.children.get(name);
   }
 
+  public containsId(id: string) {
+    return this.tryGetChild(id) !== undefined;
+  }
+
   public contains(node: GraphNode<A>) {
     return this.nodes.has(node);
   }

packages/aws-cdk-lib/pipelines/lib/helpers-internal/pipeline-graph.ts

@@ -134,7 +134,12 @@ export class PipelineGraph {
     const stackGraphs = new Map<StackDeployment, AGraph>();
 
     for (const stack of stage.stacks) {
-      const stackGraph: AGraph = Graph.of(this.simpleStackName(stack.stackName, stage.stageName), { type: 'stack-group', stack });
+      const stackGraphName = findUniqueName(retGraph, [
+        this.simpleStackName(stack.stackName, stage.stageName),
+        ...stack.account ? [stack.account] : [],
+        ...stack.region ? [stack.region] : [],
+      ]);
+      const stackGraph: AGraph = Graph.of(stackGraphName, { type: 'stack-group', stack });
       const prepareNode: AGraphNode | undefined = this.prepareStep ? aGraphNode('Prepare', { type: 'prepare', stack }) : undefined;
       const deployNode: AGraphNode = aGraphNode('Deploy', {
         type: 'execute',
@@ -412,4 +417,14 @@ function aGraphNode(id: string, x: GraphAnnotation): AGraphNode {
 
 function stripPrefix(s: string, prefix: string) {
   return s.startsWith(prefix) ? s.slice(prefix.length) : s;
+}
+
+function findUniqueName(parent: Graph<any>, parts: string[]): string {
+  for (let i = 1; i <= parts.length; i++) {
+    const candidate = parts.slice(0, i).join('.');
+    if (!parent.containsId(candidate)) {
+      return candidate;
+    }
+  }
+  return parts.join('.');
 }

packages/aws-cdk-lib/pipelines/test/compliance/basic-behavior.test.ts

@@ -81,6 +81,33 @@ test('overridden stack names are respected', () => {
   });
 });
 
+test('two stacks can have the same name', () => {
+  const pipeline = new ModernTestGitHubNpmPipeline(pipelineStack, 'Cdk', { useChangeSets: false });
+  pipeline.addStage(new TwoStacksApp(app, 'App'));
+
+  Template.fromStack(pipelineStack).hasResourceProperties('AWS::CodePipeline::Pipeline', {
+    Stages: Match.arrayWith([
+      {
+        Name: 'App',
+        Actions: Match.arrayWith([
+          Match.objectLike({
+            Name: stringLike('MyFancyStack.Deploy'),
+            Configuration: Match.objectLike({
+              StackName: 'MyFancyStack',
+            }),
+          }),
+          Match.objectLike({
+            Name: stringLike('MyFancyStack.eu-west-2.Deploy'),
+            Configuration: Match.objectLike({
+              StackName: 'MyFancyStack',
+            }),
+          }),
+        ]),
+      },
+    ]),
+  });
+});
+
 test('changing CLI version leads to a different pipeline structure (restarting it)', () => {
 
   // GIVEN
@@ -154,3 +181,17 @@ class OneStackAppWithCustomName extends Stage {
     });
   }
 }
+
+class TwoStacksApp extends Stage {
+  constructor(scope: Construct, id: string, props?: StageProps) {
+    super(scope, id, props);
+    new BucketStack(this, 'Stack1', {
+      env: { region: 'eu-west-1' },
+      stackName: 'MyFancyStack',
+    });
+    new BucketStack(this, 'Stack2', {
+      env: { region: 'eu-west-2' },
+      stackName: 'MyFancyStack',
+    });
+  }
+}