feat: check reviewer username for merge requests

Adds a new optional configuration parameter to specify a required reviewer username for merge requests. If set, the bot validates that the specified reviewer in the `BOT_GITLAB_MERGE_REQUEST_REVIEWER_USERNAME` environment variable is present in the event data `reviewers` array before processing the merge request.

Author: francovp

README.md

@@ -164,6 +164,10 @@ In GitLab, it is necessary to set a milestone when creating a merge request. By
 
 Merge requests can only be merged if the source branch is associated with an existing issue. By default, this requirement is disabled.
 
+**`BOT_GITLAB_MERGE_REQUEST_REVIEWER_USERNAME`**
+
+This parameter specifies the username of a required reviewer for merge requests. If set, merge requests will only be processed by the bot if a reviewer with this username is assigned. If not set, this check is skipped.
+
 **`OPENAI_API_BASE` / `OPENAI_API_KEY` / `OPENAI_API_MODEL`**
 
 These parameters are used to connect the OPENAI model.

src/config.py

@@ -157,3 +157,5 @@
     ).lower()
     == "true"
 )
+
+bot_gitlab_merge_request_reviewer_username = os.getenv("BOT_GITLAB_MERGE_REQUEST_REVIEWER_USERNAME", None)

src/merge_request_hook.py

@@ -29,6 +29,7 @@
     bot_gitlab_merge_request_milestone_required,
     bot_gitlab_merge_request_summary_enabled,
     bot_gitlab_username,
+    bot_gitlab_merge_request_reviewer_username,
 )
 from src.i18n import _
 from src.llm import AI, ai_diffs_summary
@@ -103,6 +104,29 @@ def check_email(commit_author_name, commit_author_email):
             )
 
 
+def has_required_reviewer(event_data):
+    """Checks if the configured required reviewer is present in the merge request reviewers list."""
+    required_username = bot_gitlab_merge_request_reviewer_username
+    if not required_username:
+        # If no required username is configured, the check passes
+        return True
+
+    reviewers = []
+    event_type = event_data.get("event_type")
+
+    if event_type == "merge_request":
+        reviewers = event_data.get("reviewers", [])
+
+    if not reviewers:
+        return False
+
+    for reviewer in reviewers:
+        if reviewer.get("username") == required_username:
+            return True
+
+    return False
+
+
 async def generate_diff_description_summary(event, gl):
     project_id = event.project_id
     description = event.data["object_attributes"]["description"]
@@ -297,15 +321,24 @@ def has_ai_review_label(labels):
 
 class MergeRequestHooks:
     async def merge_request_opened_event(self, event, gl, *args, **kwargs):
+        if not has_required_reviewer(event.data):
+            logging.debug("Required reviewer not found. Skipping merge_request_opened_event.")
+            return
         await generate_diff_description_summary(event, gl)
         await check_commit(event, gl)
 
     async def merge_request_updated_event(self, event, gl, *args, **kwargs):
+        if not has_required_reviewer(event.data):
+            logging.debug("Required reviewer not found. Skipping merge_request_updated_event.")
+            return
         if is_opened_merge_request(event):
             await generate_diff_description_summary(event, gl)
             await check_commit(event, gl)
 
     async def merge_request_reopen_event(self, event, gl, *args, **kwargs):
+        if not has_required_reviewer(event.data):
+            logging.debug("Required reviewer not found. Skipping merge_request_reopen_event.")
+            return
         await generate_diff_description_summary(event, gl)
         await check_commit(event, gl)