From 81f598ea476cbdb80c7b17b0bbdb59fc6e4add70 Mon Sep 17 00:00:00 2001
From: Eric Nielsen <4120606+ericbn@users.noreply.github.com>
Date: Thu, 31 Jul 2025 18:13:50 -0500
Subject: [PATCH] fix(parameters): fix
 _transform_and_cache_get_parameters_response

was passing positional arguments to transform_value in the wrong order,
making the latter fail miserably with

    TransformParameterError: Unable to transform value using "the value"

because value was being passed as the expected transform argument.
Use keyword arguments instead and cover this with a test.
---
 .../utilities/parameters/base.py              |  4 ++-
 .../utilities/parameters/ssm.py               |  6 ++--
 .../_boto3/test_utilities_parameters.py       | 28 +++++++++++++++++++
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/aws_lambda_powertools/utilities/parameters/base.py b/aws_lambda_powertools/utilities/parameters/base.py
index 42c15e11304..2daf4bb5642 100644
--- a/aws_lambda_powertools/utilities/parameters/base.py
+++ b/aws_lambda_powertools/utilities/parameters/base.py
@@ -187,7 +187,9 @@ def get_multiple(
             raise GetParameterError(str(exc))
 
         if transform:
-            values.update(transform_value(values, transform, raise_on_transform_error))
+            values.update(
+                transform_value(value=values, transform=transform, raise_on_transform_error=raise_on_transform_error),
+            )
 
         self.add_to_cache(key=key, value=values, max_age=max_age)
 
diff --git a/aws_lambda_powertools/utilities/parameters/ssm.py b/aws_lambda_powertools/utilities/parameters/ssm.py
index 4a1acc69227..696a80cc1c9 100644
--- a/aws_lambda_powertools/utilities/parameters/ssm.py
+++ b/aws_lambda_powertools/utilities/parameters/ssm.py
@@ -650,13 +650,13 @@ def _transform_and_cache_get_parameters_response(
             name = parameter["Name"]
             value = parameter["Value"]
             options = parameters[name]
-            transform = options.get("transform")
+            transform = options["transform"]
 
             # NOTE: If transform is set, we do it before caching to reduce number of operations
             if transform:
-                value = transform_value(name, value, transform, raise_on_error)  # type: ignore
+                value = transform_value(value=value, transform=transform, raise_on_transform_error=raise_on_error)  # type: ignore[assignment]
 
-            _cache_key = (name, options["transform"])
+            _cache_key = (name, transform)
             self.add_to_cache(key=_cache_key, value=value, max_age=options["max_age"])
 
             response[name] = value
diff --git a/tests/functional/parameters/_boto3/test_utilities_parameters.py b/tests/functional/parameters/_boto3/test_utilities_parameters.py
index da9422ea839..6f461c6a7c7 100644
--- a/tests/functional/parameters/_boto3/test_utilities_parameters.py
+++ b/tests/functional/parameters/_boto3/test_utilities_parameters.py
@@ -1114,6 +1114,34 @@ def test_ssm_provider_get_parameters_by_name_do_not_raise_on_failure(mock_name,
         stubber.deactivate()
 
 
+def test_ssm_provider_get_parameters_by_name_do_not_raise_on_failure_transform(mock_name, mock_value, config):
+    success = f"/dev/{mock_name}"
+    fail = f"/prod/{mock_name}"
+    params = {success: {}, fail: {}}
+    param_names = list(params.keys())
+    expected_value = {"value": mock_value}
+    stub_params = {success: json.dumps(expected_value)}
+
+    expected_stub_response = build_get_parameters_stub(params=stub_params, invalid_parameters=[fail])
+    expected_stub_params = {"Names": param_names}
+
+    provider = parameters.SSMProvider(boto_config=config)
+    stubber = stub.Stubber(provider.client)
+    stubber.add_response("get_parameters", expected_stub_response, expected_stub_params)
+    stubber.activate()
+
+    try:
+        ret = provider.get_parameters_by_name(parameters=params, transform="json", raise_on_error=False)
+
+        stubber.assert_no_pending_responses()
+        assert ret[success] == expected_value
+        assert ret["_errors"]
+        assert len(ret["_errors"]) == 1
+        assert fail not in ret
+    finally:
+        stubber.deactivate()
+
+
 def test_ssm_provider_get_parameters_by_name_do_not_raise_on_failure_with_decrypt(mock_name, config):
     # GIVEN one parameter requires decryption and an arbitrary SDK error occurs
     param = f"/{mock_name}"