fix(lambda-nodejs): incorrect SDK v2 warning generated (#27014)

Fixes to remove an incorrectly generated warning when using Node JS runtime <= 16 with `NodejsFunction`

Closes #26966 

----

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

Author: plumdog

packages/aws-cdk-lib/aws-lambda-nodejs/lib/bundling.ts

@@ -137,7 +137,7 @@ export class Bundling implements cdk.BundlingOptions {
     // their environment.
     if (isV2Runtime && externals.some((pkgName) => pkgName.startsWith('@aws-sdk/'))) {
       cdk.Annotations.of(scope).addWarningV2('@aws-cdk/aws-lambda-nodejs:sdkV3NotInRuntime', 'If you are relying on AWS SDK v3 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 18 or higher.');
-    } else if (externals.includes('aws-sdk')) {
+    } else if (!isV2Runtime && externals.includes('aws-sdk')) {
       cdk.Annotations.of(scope).addWarningV2('@aws-cdk/aws-lambda-nodejs:sdkV2NotInRuntime', 'If you are relying on AWS SDK v2 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 16 or lower.');
     }
 

packages/aws-cdk-lib/aws-lambda-nodejs/test/bundling.test.ts

@@ -882,6 +882,24 @@ test('bundling with <= Node16 warns when sdk v3 is external', () => {
   );
 });
 
+test('bundling with <= Node16 does not warn with default externalModules', () => {
+  const myStack = new Stack(app, 'MyTestStack2');
+  Bundling.bundle(myStack, {
+    entry,
+    projectRoot,
+    depsLockFilePath,
+    runtime: Runtime.NODEJS_16_X,
+    architecture: Architecture.X86_64,
+  });
+
+  Annotations.fromStack(myStack).hasNoWarning('*',
+    'If you are relying on AWS SDK v3 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 18 or higher. [ack: @aws-cdk/aws-lambda-nodejs:sdkV3NotInRuntime]',
+  );
+  Annotations.fromStack(myStack).hasNoWarning('*',
+    'If you are relying on AWS SDK v2 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 16 or lower. [ack: @aws-cdk/aws-lambda-nodejs:sdkV2NotInRuntime]',
+  );
+});
+
 test('bundling with >= Node18 warns when sdk v3 is external', () => {
   Bundling.bundle(stack, {
     entry,
@@ -897,6 +915,24 @@ test('bundling with >= Node18 warns when sdk v3 is external', () => {
   );
 });
 
+test('bundling with >= Node18 does not warn with default externalModules', () => {
+  const myStack = new Stack(app, 'MyTestStack3');
+  Bundling.bundle(myStack, {
+    entry,
+    projectRoot,
+    depsLockFilePath,
+    runtime: Runtime.NODEJS_18_X,
+    architecture: Architecture.X86_64,
+  });
+
+  Annotations.fromStack(myStack).hasNoWarning('*',
+    'If you are relying on AWS SDK v3 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 18 or higher. [ack: @aws-cdk/aws-lambda-nodejs:sdkV3NotInRuntime]',
+  );
+  Annotations.fromStack(myStack).hasNoWarning('*',
+    'If you are relying on AWS SDK v2 to be present in the Lambda environment already, please explicitly configure a NodeJS runtime of Node 16 or lower. [ack: @aws-cdk/aws-lambda-nodejs:sdkV2NotInRuntime]',
+  );
+});
+
 test('bundling with NODEJS_LATEST warns when any dependencies are external', () => {
   Bundling.bundle(stack, {
     entry,