feat: option to configure partition with env var (#895)

Adds support for deployment to aws-cn partition by checking an optional environemt variable, `CDK_AWS_PARTITION`. The partition is currently not available to the pipeline in the `jobForDeploy`, adding the environment variable is a non-breaking change to get the pipeline to deploy to aws-cn.

This has been verified with stacks and nested stacks in multiple stages in aws-cn.

Fixes #820

README.md

@@ -44,6 +44,7 @@ Workflows.
       - [Manual Approval Step](#manual-approval-step)
     - [Pipeline YAML Comments](#pipeline-yaml-comments)
     - [Common Configuration for Docker Asset Publishing Steps](#common-configuration-for-docker-asset-publishing)
+  - [AWS China partition support](#aws-china-partition-support)
   - [Tutorial](#tutorial)
   - [Not supported yet](#not-supported-yet)
   - [Contributing](#contributing)
@@ -644,6 +645,19 @@ const pipeline = new GitHubWorkflow(app, 'Pipeline', {
 app.synth();
 ```
 
+## AWS China partition support
+
+The `CDK_AWS_PARTITION` environment variable can be used to specify the AWS partition for the pipeline.
+If it's specified to `aws-cn`, the assets generated by pipeline will reference the resources in
+`.amazonaws.com.cn` instead of `.amazonaws.com`.
+
+If `CDK_AWS_PARTITION` environment variable is not specified, the default behaviour for the pipeline is
+to use the `aws` partition.
+
+It is not possible to have a pipeline that deploys to both `aws` and `aws-cn` partitions.
+If you need to deploy to both partitions, you will need to create two separate pipelines.
+The stages and stacks can be shared between the two pipelines.
+
 ## Tutorial
 
 You can find an example usage in [test/example-app.ts](./test/example-app.ts)

src/pipeline.ts

@@ -602,10 +602,11 @@ export class GitHubWorkflow extends PipelineBase {
     }
 
     const resolve = (s: string): string => {
+      const partition = process.env.CDK_AWS_PARTITION ?? 'aws';
       return EnvironmentPlaceholders.replace(s, {
         accountId: account,
         region: region,
-        partition: 'aws',
+        partition: partition,
       });
     };
 
@@ -614,7 +615,10 @@ export class GitHubWorkflow extends PipelineBase {
       if (this.assetHashMap[hash] === undefined) {
         throw new Error(`Template asset hash ${hash} not found.`);
       }
-      return template.replace(hash, `\${{ needs.${this.assetHashMap[hash]}.outputs.${ASSET_HASH_NAME} }}`);
+      const updated_template = template.replace(hash, `\${{ needs.${this.assetHashMap[hash]}.outputs.${ASSET_HASH_NAME} }}`);
+      return process.env.CDK_AWS_PARTITION == 'aws-cn'
+        ? updated_template.replace('.amazonaws.com', '.amazonaws.com.cn')
+        : updated_template;
     };
 
     const params: Record<string, any> = {