From 4127cb7b9f78beb18d50e15c5ba91cfbb937dba6 Mon Sep 17 00:00:00 2001
From: JohannesKoenigTMH <112848318+JohannesKoenigTMH@users.noreply.github.com>
Date: Mon, 20 Nov 2023 23:43:13 +0100
Subject: [PATCH] LakeFormation: raise AlreadyExistsException when registering
 an existing resource (#7052)

---
 moto/lakeformation/exceptions.py               | 5 +++++
 moto/lakeformation/models.py                   | 6 +++++-
 tests/test_lakeformation/test_lakeformation.py | 6 +++---
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/moto/lakeformation/exceptions.py b/moto/lakeformation/exceptions.py
index a0e3b4a17..86727c390 100644
--- a/moto/lakeformation/exceptions.py
+++ b/moto/lakeformation/exceptions.py
@@ -10,3 +10,8 @@ class EntityNotFound(JsonRESTError):
 class InvalidInput(JsonRESTError):
     def __init__(self, message: str) -> None:
         super().__init__("InvalidInputException", message)
+
+
+class AlreadyExists(JsonRESTError):
+    def __init__(self, message: str) -> None:
+        super().__init__("AlreadyExistsException", message)
diff --git a/moto/lakeformation/models.py b/moto/lakeformation/models.py
index f1217b93a..796242174 100644
--- a/moto/lakeformation/models.py
+++ b/moto/lakeformation/models.py
@@ -4,7 +4,7 @@ from typing import Any, Dict, List, Tuple, Optional
 
 from moto.core import BaseBackend, BackendDict, BaseModel
 from moto.utilities.tagging_service import TaggingService
-from .exceptions import EntityNotFound, InvalidInput
+from .exceptions import EntityNotFound, InvalidInput, AlreadyExists
 
 
 class RessourceType(Enum):
@@ -187,6 +187,10 @@ class LakeFormationBackend(BaseBackend):
         del self.resources[resource_arn]
 
     def register_resource(self, resource_arn: str, role_arn: str) -> None:
+        if resource_arn in self.resources:
+            raise AlreadyExists(
+                "An error occurred (AlreadyExistsException) when calling the RegisterResource operation: Resource is already registered"
+            )
         self.resources[resource_arn] = Resource(resource_arn, role_arn)
 
     def list_resources(self) -> List[Resource]:
diff --git a/tests/test_lakeformation/test_lakeformation.py b/tests/test_lakeformation/test_lakeformation.py
index d2501c2f7..3a72f6d88 100644
--- a/tests/test_lakeformation/test_lakeformation.py
+++ b/tests/test_lakeformation/test_lakeformation.py
@@ -13,12 +13,12 @@ from moto import mock_lakeformation
 @mock_lakeformation
 def test_register_resource():
     client = boto3.client("lakeformation", region_name="us-east-2")
-    resp = client.register_resource(
-        ResourceArn="some arn",
-    )
+    resp = client.register_resource(ResourceArn="some arn", RoleArn="another arn")
 
     del resp["ResponseMetadata"]
     assert resp == {}
+    with pytest.raises(client.exceptions.AlreadyExistsException):
+        client.register_resource(ResourceArn="some arn", RoleArn="another arn")
 
 
 @mock_lakeformation