fix(parameters): preserve original stack trace on transform failures …

packages/parameters/src/base/BaseProvider.ts

@@ -167,11 +167,19 @@ abstract class BaseProvider implements BaseProviderInterface {
             entryKey
           );
         } catch (error) {
-          if (configs.throwOnTransformError)
-            throw new TransformParameterError(
+          if (configs.throwOnTransformError) {
+            if (error instanceof TransformParameterError) {
+              throw error;
+            }
+
+            // Otherwise wrap—but preserve the original stack
+            const wrapped = new TransformParameterError(
               configs.transform,
               (error as Error).message
             );
+            wrapped.stack = (error as Error).stack;
+            throw wrapped;
+          }
         }
       }
     }

packages/parameters/tests/unit/BaseProvider.test.ts

@@ -24,7 +24,7 @@ vi.mock('@aws-lambda-powertools/commons', async (importOriginal) => ({
 class TestProvider extends BaseProvider {
   public constructor() {
     super({
-      proto: class {
+      awsSdkV3ClientPrototype: class {
         #name = 'TestProvider';
 
         public hello(): string {
@@ -389,7 +389,7 @@ describe('Class: BaseProvider', () => {
       });
     });
 
-    it('throws when called with a binary transform and throwOnTransformError equal to TRUE, and at least ONE the values is NOT a valid string representation of a binary', async () => {
+    it('throws a TransformParameterError when trying to transform an invalid binary and throwOnTransformError is enabled', async () => {
       // Prepare
       const mockData = { A: 'qw' };
       const provider = new TestProvider();
@@ -404,6 +404,22 @@ describe('Class: BaseProvider', () => {
       ).rejects.toThrowError(TransformParameterError);
     });
 
+    it('throws a TransformParameterError when a runtime error occurs during the transformation and throwOnTransformError is enabled', async () => {
+      // Prepare
+      const mockData = { A: 'foo' };
+      const provider = new TestProvider();
+      vi.spyOn(provider, '_getMultiple').mockResolvedValue(mockData);
+
+      // Act & Assess
+      await expect(
+        provider.getMultiple('my-path', {
+          // @ts-ignore - we want to test an unexpected runtime error
+          transform: 1,
+          throwOnTransformError: true,
+        })
+      ).rejects.toThrowError(TransformParameterError);
+    });
+
     it('returns an object with the transformed values when auto transform is used and the key of the parameter ends with `.binary`', async () => {
       // Prepare
       const mockData = { 'A.binary': toBase64(encoder.encode('my-value')) };