Allow zero submission rate limits

src/kernelbot/api/main.py

@@ -1131,8 +1131,8 @@ async def admin_set_rate_limit(
     if mode_category not in ("test", "leaderboard"):
         raise HTTPException(status_code=400, detail="mode_category must be 'test' or 'leaderboard'")
     max_per_hour = payload.get("max_submissions_per_hour")
-    if not isinstance(max_per_hour, int) or max_per_hour < 1:
-        raise HTTPException(status_code=400, detail="max_submissions_per_hour must be a positive integer")
+    if not isinstance(max_per_hour, int) or max_per_hour < 0:
+        raise HTTPException(status_code=400, detail="max_submissions_per_hour must be a non-negative integer")
     try:
         with db_context as db:
             result = db.set_rate_limit(leaderboard_name, mode_category, max_per_hour)

src/migrations/20260319_01_allow-zero-rate-limits.py

@@ -0,0 +1,28 @@
+"""
+Allow zero-submission rate limits.
+"""
+
+from yoyo import step
+
+__depends__ = {"20260318_01_ban-user"}
+
+steps = [
+    step(
+        """
+        ALTER TABLE leaderboard.rate_limit
+        DROP CONSTRAINT rate_limit_max_submissions_per_hour_check;
+
+        ALTER TABLE leaderboard.rate_limit
+        ADD CONSTRAINT rate_limit_max_submissions_per_hour_check
+        CHECK (max_submissions_per_hour >= 0);
+        """,
+        """
+        ALTER TABLE leaderboard.rate_limit
+        DROP CONSTRAINT rate_limit_max_submissions_per_hour_check;
+
+        ALTER TABLE leaderboard.rate_limit
+        ADD CONSTRAINT rate_limit_max_submissions_per_hour_check
+        CHECK (max_submissions_per_hour > 0);
+        """,
+    )
+]

tests/test_admin_api.py

@@ -800,11 +800,11 @@ def test_set_rate_limit_invalid_category(self, test_client):
         assert response.status_code == 400
 
     def test_set_rate_limit_invalid_count(self, test_client):
-        """PUT /admin/leaderboards/{name}/rate-limits rejects non-positive count."""
+        """PUT /admin/leaderboards/{name}/rate-limits rejects negative count."""
         response = test_client.put(
             "/admin/leaderboards/test-lb/rate-limits",
             headers={"Authorization": "Bearer test_token"},
-            json={"mode_category": "test", "max_submissions_per_hour": 0},
+            json={"mode_category": "test", "max_submissions_per_hour": -1},
         )
         assert response.status_code == 400
 

tests/test_leaderboard_db.py

@@ -1153,6 +1153,16 @@ def test_check_rate_limit_no_config(database, submit_leaderboard):
         assert result is None
 
 
+def test_check_rate_limit_zero_limit_blocks_submissions(database, submit_leaderboard):
+    """A zero rate limit keeps a leaderboard visible while rejecting submissions."""
+    with database as db:
+        db.set_rate_limit("submit-leaderboard", "leaderboard", 0)
+        result = db.check_rate_limit("submit-leaderboard", "123", "leaderboard")
+        assert result["allowed"] is False
+        assert result["current_count"] == 0
+        assert result["max_per_hour"] == 0
+
+
 def test_check_rate_limit_under_limit(database, submit_leaderboard):
     """check_rate_limit allows submissions under the limit."""
     with database as db: