feat(cli): control library init version with a command-line parameter

packages/aws-cdk/lib/init.ts

@@ -490,18 +490,18 @@ interface Versions {
  * This has been built into the CLI at build time.
  */
 async function loadInitVersions(): Promise<Versions> {
-  const recommendedFlagsFile = path.join(__dirname, './init-templates/.init-version.json');
-  const contents = JSON.parse(await fs.readFile(recommendedFlagsFile, { encoding: 'utf-8' }));
+  const initVersionFile = path.join(__dirname, './init-templates/.init-version.json');
+  const contents = JSON.parse(await fs.readFile(initVersionFile, { encoding: 'utf-8' }));
 
   const ret = {
-    'aws-cdk-lib': contents['aws-cdk-lib'],
+    'aws-cdk-lib': process.env.CDK_INIT_LIB_VERSION ?? contents['aws-cdk-lib'],
     'constructs': contents.constructs,
     'aws-cdk': versionNumber(),
   };
   for (const [key, value] of Object.entries(ret)) {
     /* istanbul ignore next */
     if (!value) {
-      throw new ToolkitError(`Missing init version from ${recommendedFlagsFile}: ${key}`);
+      throw new ToolkitError(`Missing init version from ${initVersionFile}: ${key}`);
     }
   }
 

packages/aws-cdk/test/init.test.ts

@@ -17,6 +17,23 @@ describe('constructs version', () => {
     expect(await fs.pathExists(path.join(workDir, 'lib'))).toBeTruthy();
   });
 
+  cliTest('can override requested version with environment variable', async (workDir) => {
+    process.env.CDK_INIT_LIB_VERSION = '2.100';
+    try {
+      await cliInit({
+        type: 'lib',
+        language: 'typescript',
+        workDir,
+      });
+
+      // Check that package.json and lib/ got created in the current directory
+      const pj = JSON.parse(await fs.readFile(path.join(workDir, 'package.json'), 'utf-8'));
+      expect(Object.entries(pj.devDependencies)).toContainEqual(['aws-cdk-lib', '2.100']);
+    } finally {
+      delete process.env.CDK_INIT_LIB_VERSION;
+    }
+  });
+
   cliTest('asking for a nonexistent template fails', async (workDir) => {
     await expect(cliInit({
       type: 'banana',