From 6f7dcda0fb87166bd1396a1c5391f9eff3a2af18 Mon Sep 17 00:00:00 2001
From: Cristopher Pinzon <cristopher.pinzon@gmail.com>
Date: Wed, 22 Jan 2025 15:47:16 +0100
Subject: [PATCH] fix cfn template join with noValue

---
 .../engine/template_deployer.py               |  4 ++-
 .../cloudformation/test_template_engine.py    | 10 ++++++
 .../test_template_engine.snapshot.json        | 10 ++++++
 .../test_template_engine.validation.json      |  3 ++
 tests/aws/templates/engine/join_no_value.yml  | 34 +++++++++++++++++++
 5 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 tests/aws/templates/engine/join_no_value.yml

diff --git a/localstack-core/localstack/services/cloudformation/engine/template_deployer.py b/localstack-core/localstack/services/cloudformation/engine/template_deployer.py
index 3180a820baf16..5a451e5171a73 100644
--- a/localstack-core/localstack/services/cloudformation/engine/template_deployer.py
+++ b/localstack-core/localstack/services/cloudformation/engine/template_deployer.py
@@ -420,7 +420,9 @@ def _resolve_refs_recursively(
                 raise Exception(
                     f"Cannot resolve CF Fn::Join {value} due to null values: {join_values}"
                 )
-            return value[keys_list[0]][0].join([str(v) for v in join_values])
+            return value[keys_list[0]][0].join(
+                [str(v) for v in join_values if v != "__aws_no_value__"]
+            )
 
         if stripped_fn_lower == "sub":
             item_to_sub = value[keys_list[0]]
diff --git a/tests/aws/services/cloudformation/test_template_engine.py b/tests/aws/services/cloudformation/test_template_engine.py
index c6da516eac01d..d039307ef5101 100644
--- a/tests/aws/services/cloudformation/test_template_engine.py
+++ b/tests/aws/services/cloudformation/test_template_engine.py
@@ -263,6 +263,16 @@ def test_sub_number_type(self, deploy_cfn_template):
         assert stack.outputs["Threshold"] == threshold
         assert stack.outputs["Period"] == period
 
+    @markers.aws.validated
+    def test_join_no_value_construct(self, deploy_cfn_template, snapshot, aws_client):
+        stack = deploy_cfn_template(
+            template_path=os.path.join(
+                os.path.dirname(__file__), "../../templates/engine/join_no_value.yml"
+            )
+        )
+
+        snapshot.match("join-output", stack.outputs)
+
 
 class TestImports:
     @markers.aws.validated
diff --git a/tests/aws/services/cloudformation/test_template_engine.snapshot.json b/tests/aws/services/cloudformation/test_template_engine.snapshot.json
index df326dbfcbbeb..da52914bdd544 100644
--- a/tests/aws/services/cloudformation/test_template_engine.snapshot.json
+++ b/tests/aws/services/cloudformation/test_template_engine.snapshot.json
@@ -673,5 +673,15 @@
         }
       }
     }
+  },
+  "tests/aws/services/cloudformation/test_template_engine.py::TestIntrinsicFunctions::test_join_no_value_construct": {
+    "recorded-date": "22-01-2025, 14:01:46",
+    "recorded-content": {
+      "join-output": {
+        "JoinConditionalNoValue": "",
+        "JoinOnlyNoValue": "",
+        "JoinWithNoValue": "Sample"
+      }
+    }
   }
 }
diff --git a/tests/aws/services/cloudformation/test_template_engine.validation.json b/tests/aws/services/cloudformation/test_template_engine.validation.json
index 91f44725ce40d..e0bbb0be7e342 100644
--- a/tests/aws/services/cloudformation/test_template_engine.validation.json
+++ b/tests/aws/services/cloudformation/test_template_engine.validation.json
@@ -35,6 +35,9 @@
   "tests/aws/services/cloudformation/test_template_engine.py::TestIntrinsicFunctions::test_get_azs_function[us-west-2]": {
     "last_validated_date": "2024-05-09T08:33:45+00:00"
   },
+  "tests/aws/services/cloudformation/test_template_engine.py::TestIntrinsicFunctions::test_join_no_value_construct": {
+    "last_validated_date": "2025-01-22T14:01:46+00:00"
+  },
   "tests/aws/services/cloudformation/test_template_engine.py::TestIntrinsicFunctions::test_sub_number_type": {
     "last_validated_date": "2024-08-09T06:55:16+00:00"
   },
diff --git a/tests/aws/templates/engine/join_no_value.yml b/tests/aws/templates/engine/join_no_value.yml
new file mode 100644
index 0000000000000..c974faff820f0
--- /dev/null
+++ b/tests/aws/templates/engine/join_no_value.yml
@@ -0,0 +1,34 @@
+Conditions:
+  active: !Equals [ true, true ]
+  inactive: !Equals [ true, false ]
+
+Resources:
+  Parameter:
+    Type: AWS::SSM::Parameter
+    Properties:
+      Type: String
+      Value: Sample
+      Name: commands 
+
+Outputs:
+  JoinWithNoValue:
+    Value:
+      Fn::Join:
+        - ","
+        - - !GetAtt Parameter.Value
+          - !Ref AWS::NoValue
+
+  JoinOnlyNoValue:
+    Value:
+      Fn::Join:
+        - ","
+        - - !Ref AWS::NoValue
+
+  JoinConditionalNoValue:
+    Value:
+      Fn::Join:
+        - ","
+        - - Fn::If:
+              - active
+              - !Ref AWS::NoValue
+              - !Ref AWS::NoValue