From 7e88a901d9ed7612d92bdeb9dd67056c99bf3126 Mon Sep 17 00:00:00 2001
From: stromp <valkjes@gmail.com>
Date: Tue, 1 Mar 2022 23:50:42 +0100
Subject: [PATCH] fix for duplicate tag keys in secretsmanager (#4900)

---
 moto/secretsmanager/models.py                    | 10 ++++++++++
 tests/test_secretsmanager/test_secretsmanager.py |  6 ++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/moto/secretsmanager/models.py b/moto/secretsmanager/models.py
index 783f9542d..b04b51dae 100644
--- a/moto/secretsmanager/models.py
+++ b/moto/secretsmanager/models.py
@@ -735,6 +735,16 @@ class SecretsManagerBackend(BaseBackend):
         old_tags = secret.tags
 
         for tag in tags:
+            existing_key_name = next(
+                (
+                    old_key
+                    for old_key in old_tags
+                    if old_key.get("Key") == tag.get("Key")
+                ),
+                None,
+            )
+            if existing_key_name:
+                old_tags.remove(existing_key_name)
             old_tags.append(tag)
 
         return secret_id
diff --git a/tests/test_secretsmanager/test_secretsmanager.py b/tests/test_secretsmanager/test_secretsmanager.py
index 62ebc721b..48c69c4c8 100644
--- a/tests/test_secretsmanager/test_secretsmanager.py
+++ b/tests/test_secretsmanager/test_secretsmanager.py
@@ -1282,14 +1282,16 @@ def test_tag_resource(pass_arn):
     conn.tag_resource(
         SecretId=secret_id, Tags=[{"Key": "FirstTag", "Value": "SomeValue"},],
     )
-
+    conn.tag_resource(
+        SecretId="test-secret", Tags=[{"Key": "FirstTag", "Value": "SomeOtherValue"},],
+    )
     conn.tag_resource(
         SecretId=secret_id, Tags=[{"Key": "SecondTag", "Value": "AnotherValue"},],
     )
 
     secrets = conn.list_secrets()
     assert secrets["SecretList"][0].get("Tags") == [
-        {"Key": "FirstTag", "Value": "SomeValue"},
+        {"Key": "FirstTag", "Value": "SomeOtherValue"},
         {"Key": "SecondTag", "Value": "AnotherValue"},
     ]