fix(codepipeline-actions): use token as CodeCommitSourceAction branch

packages/@aws-cdk/aws-codepipeline-actions/lib/codecommit/source-action.ts

@@ -2,7 +2,7 @@ import * as codecommit from '@aws-cdk/aws-codecommit';
 import * as codepipeline from '@aws-cdk/aws-codepipeline';
 import * as targets from '@aws-cdk/aws-events-targets';
 import * as iam from '@aws-cdk/aws-iam';
-import { Construct } from '@aws-cdk/core';
+import { Construct, Token } from '@aws-cdk/core';
 import { Action } from '../action';
 import { sourceArtifactBounds } from '../common';
 
@@ -122,8 +122,8 @@ export class CodeCommitSourceAction extends Action {
     const createEvent = this.props.trigger === undefined ||
       this.props.trigger === CodeCommitTrigger.EVENTS;
     if (createEvent) {
-      const branchIdDisambiguator = this.branch === 'master' ? '' : `-${this.branch}-`;
-      this.props.repository.onCommit(`${stage.pipeline.node.uniqueId}${branchIdDisambiguator}EventRule`, {
+      const eventId = this.generateEventId(stage);
+      this.props.repository.onCommit(eventId, {
         target: new targets.CodePipeline(stage.pipeline),
         branches: [this.branch],
       });
@@ -153,4 +153,24 @@ export class CodeCommitSourceAction extends Action {
       },
     };
   }
+
+  private generateEventId(stage: codepipeline.IStage): string {
+    const baseId = stage.pipeline.node.uniqueId;
+    if (Token.isUnresolved(this.branch)) {
+      let candidate = '';
+      let counter = 0;
+      do {
+        candidate = this.eventIdFromPrefix(`${baseId}${counter}`);
+        counter += 1;
+      } while (this.props.repository.node.tryFindChild(candidate) !== undefined);
+      return candidate;
+    } else {
+      const branchIdDisambiguator = this.branch === 'master' ? '' : '-${this.branch}-';
+      return this.eventIdFromPrefix(`${baseId}${branchIdDisambiguator}`);
+    }
+  }
+
+  private eventIdFromPrefix(eventIdPrefix: string) {
+    return `${eventIdPrefix}EventRule`;
+  }
 }

packages/@aws-cdk/aws-codepipeline-actions/test/codecommit/test.codecommit-source-action.ts

@@ -2,7 +2,7 @@ import { countResources, expect, haveResourceLike, not } from '@aws-cdk/assert';
 import * as codebuild from '@aws-cdk/aws-codebuild';
 import * as codecommit from '@aws-cdk/aws-codecommit';
 import * as codepipeline from '@aws-cdk/aws-codepipeline';
-import { Stack } from '@aws-cdk/core';
+import { Stack, Lazy } from '@aws-cdk/core';
 import { Test } from 'nodeunit';
 import * as cpactions from '../../lib';
 
@@ -224,6 +224,49 @@ export = {
 
       test.done();
     },
+
+    'allows using a Token for the branch name'(test: Test) {
+      const stack = new Stack();
+
+      const sourceOutput = new codepipeline.Artifact();
+      new codepipeline.Pipeline(stack, 'P', {
+        stages: [
+          {
+            stageName: 'Source',
+            actions: [
+              new cpactions.CodeCommitSourceAction({
+                actionName: 'CodeCommit',
+                repository: new codecommit.Repository(stack, 'R', {
+                  repositoryName: 'repository',
+                }),
+                branch: Lazy.stringValue({ produce: () => 'my-branch' }),
+                output: sourceOutput,
+              }),
+            ],
+          },
+          {
+            stageName: 'Build',
+            actions: [
+              new cpactions.CodeBuildAction({
+                actionName: 'Build',
+                project: new codebuild.PipelineProject(stack, 'CodeBuild'),
+                input: sourceOutput,
+              }),
+            ],
+          },
+        ],
+      });
+
+      expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+        EventPattern: {
+          detail: {
+            referenceName: ['my-branch'],
+          },
+        },
+      }));
+
+      test.done();
+    },
   },
 };