feat(api): add support for topics merge API

2 files changed, 43 insertions, 1 deletions

diff --git a/gitlab/exceptions.py b/gitlab/exceptions.py
index 613e9a0..97f097d 100644
--- a/gitlab/exceptions.py
+++ b/gitlab/exceptions.py
@@ -221,6 +221,10 @@ class GitlabTodoError(GitlabOperationError):
     pass
 
 
+class GitlabTopicMergeError(GitlabOperationError):
+    pass
+
+
 class GitlabTimeTrackingError(GitlabOperationError):
     pass
 
diff --git a/gitlab/v4/objects/topics.py b/gitlab/v4/objects/topics.py
index 143759d..995ff8b 100644
--- a/gitlab/v4/objects/topics.py
+++ b/gitlab/v4/objects/topics.py
@@ -1,5 +1,7 @@
-from typing import Any, cast, Union
+from typing import Any, cast, Dict, TYPE_CHECKING, Union
 
+from gitlab import cli
+from gitlab import exceptions as exc
 from gitlab import types
 from gitlab.base import RESTManager, RESTObject
 from gitlab.mixins import CRUDMixin, ObjectDeleteMixin, SaveMixin
@@ -29,3 +31,39 @@ class TopicManager(CRUDMixin, RESTManager):
 
     def get(self, id: Union[str, int], lazy: bool = False, **kwargs: Any) -> Topic:
         return cast(Topic, super().get(id=id, lazy=lazy, **kwargs))
+
+    @cli.register_custom_action(
+        "TopicManager",
+        mandatory=("source_topic_id", "target_topic_id"),
+    )
+    @exc.on_http_error(exc.GitlabMRClosedError)
+    def merge(
+        self,
+        source_topic_id: Union[int, str],
+        target_topic_id: Union[int, str],
+        **kwargs: Any,
+    ) -> Dict[str, Any]:
+        """Merge two topics, assigning all projects to the target topic.
+
+        Args:
+            source_topic_id: ID of source project topic
+            target_topic_id: ID of target project topic
+            **kwargs: Extra options to send to the server (e.g. sudo)
+
+        Raises:
+            GitlabAuthenticationError: If authentication is not correct
+            GitlabTopicMergeError: If the merge failed
+
+        Returns:
+            The merged topic data (*not* a RESTObject)
+        """
+        path = f"{self.path}/merge"
+        data = {
+            "source_topic_id": source_topic_id,
+            "target_topic_id": target_topic_id,
+        }
+
+        server_data = self.gitlab.http_post(path, post_data=data, **kwargs)
+        if TYPE_CHECKING:
+            assert isinstance(server_data, dict)
+        return server_data