fix(cli): user agent is reported as undefined/undefined (aws#24663)

Our CLI's user agent is reported as `undefined/undefined`. This is because we are reading the package name and version from the CLI's `package.json` by using a relative path to the source file (using `__dirname`). However, since a good long while, our production CLI is being bundled using `esbuild` into a single JavaScript file. This means that at runtime, `__dirname` points to a completely different directory than the one it's been coded against, and so reading the `package.json` fails.

Account for this by using a function that searches for `package.json`; still do it defensively so that if some other condition we didn't predict causes the search to fail, our CLI doesn't fail.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk/lib/api/aws-auth/sdk-provider.ts

@@ -10,6 +10,7 @@ import { cached } from './cached';
 import { CredentialPlugins } from './credential-plugins';
 import { Mode } from './credentials';
 import { ISDK, SDK, isUnrecoverableAwsError } from './sdk';
+import { rootDir } from '../../util/directories';
 import { traceMethods } from '../../util/tracing';
 
 
@@ -417,9 +418,7 @@ function parseHttpOptions(options: SdkHttpOptions) {
 
   let userAgent = options.userAgent;
   if (userAgent == null) {
-    // Find the package.json from the main toolkit
-    const pkg = JSON.parse(readIfPossible(path.join(__dirname, '..', '..', '..', 'package.json')) ?? '{}');
-    userAgent = `${pkg.name}/${pkg.version}`;
+    userAgent = defaultCliUserAgent();
   }
   config.customUserAgent = userAgent;
 
@@ -444,6 +443,20 @@ function parseHttpOptions(options: SdkHttpOptions) {
   return config;
 }
 
+/**
+ * Find the package.json from the main toolkit.
+ *
+ * If we can't read it for some reason, try to do something reasonable anyway.
+ * Fall back to argv[1], or a standard string if that is undefined for some reason.
+ */
+export function defaultCliUserAgent() {
+  const root = rootDir(false);
+  const pkg = JSON.parse((root ? readIfPossible(path.join(root, 'package.json')) : undefined) ?? '{}');
+  const name = pkg.name ?? path.basename(process.argv[1] ?? 'cdk-cli');
+  const version = pkg.version ?? '<unknown>';
+  return `${name}/${version}`;
+}
+
 /**
  * Find and return a CA certificate bundle path to be passed into the SDK.
  */

packages/aws-cdk/lib/util/directories.ts

@@ -28,15 +28,27 @@ export function cdkCacheDir() {
   return path.join(cdkHomeDir(), 'cache');
 }
 
-export function rootDir() {
-
-  function _rootDir(dirname: string): string {
+/**
+ * From the current file, find the directory that contains the CLI's package.json
+ *
+ * Can't use `__dirname` in production code, as the CLI will get bundled as it's
+ * released and `__dirname` will refer to a different location in the `.ts` form
+ * as it will in the final executing form.
+ */
+export function rootDir(): string;
+export function rootDir(fail: true): string;
+export function rootDir(fail: false): string | undefined;
+export function rootDir(fail?: boolean) {
+  function _rootDir(dirname: string): string | undefined {
     const manifestPath = path.join(dirname, 'package.json');
     if (fs.existsSync(manifestPath)) {
       return dirname;
     }
     if (path.dirname(dirname) === dirname) {
-      throw new Error('Unable to find package manifest');
+      if (fail ?? true) {
+        throw new Error('Unable to find package manifest');
+      }
+      return undefined;
     }
     return _rootDir(path.dirname(dirname));
   }

packages/aws-cdk/test/api/sdk-provider.test.ts

@@ -5,7 +5,7 @@ import type { ConfigurationOptions } from 'aws-sdk/lib/config-base';
 import * as promptly from 'promptly';
 import * as uuid from 'uuid';
 import { FakeSts, RegisterRoleOptions, RegisterUserOptions } from './fake-sts';
-import { ISDK, Mode, SDK, SdkProvider } from '../../lib/api/aws-auth';
+import { ISDK, Mode, SDK, SdkProvider, defaultCliUserAgent } from '../../lib/api/aws-auth';
 import { PluginHost } from '../../lib/api/plugin';
 import * as logging from '../../lib/logging';
 import * as bockfs from '../bockfs';
@@ -623,6 +623,10 @@ test('even when using a profile to assume another profile, STS calls goes throug
   expect(called).toEqual(true);
 });
 
+test('default useragent is reasonable', () => {
+  expect(defaultCliUserAgent()).toContain('aws-cdk/');
+});
+
 /**
  * Use object hackery to get the credentials out of the SDK object
  */