github: don't request reviews if no diff from current reviewer list

Author: yasunariw

lib/action.ml

@@ -211,7 +211,7 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
   let do_github_tasks ctx (req : Github.t) =
     let cfg = Context.get_config_exn ctx in
     let project_owners (pull_request : pull_request) repository number =
-      match Github.get_project_owners pull_request.labels cfg.project_owners with
+      match Github.get_project_owners pull_request cfg.project_owners with
       | Some reviewers ->
         ( match%lwt Github_api.request_reviewers ~ctx ~repo:repository ~number ~reviewers with
         | Ok () -> Lwt.return_unit

lib/github.ml

@@ -140,8 +140,8 @@ let gh_link_of_string url_str =
     end
   | _ | (exception Re2.Exceptions.Regex_match_failed _) -> None
 
-let get_project_owners (labels : label list) ({ rules } : Config_t.project_owners) =
-  List.fold_left labels ~init:[] ~f:(fun acc l -> List.rev_append (Rule.Project_owners.match_rules l ~rules) acc)
+let get_project_owners (pr : pull_request) ({ rules } : Config_t.project_owners) =
+  List.fold_left pr.labels ~init:[] ~f:(fun acc l -> List.rev_append (Rule.Project_owners.match_rules l ~rules) acc)
   |> List.dedup_and_sort ~compare:String.compare
   |> List.partition_map ~f:(fun reviewer ->
        try
@@ -150,4 +150,8 @@ let get_project_owners (labels : label list) ({ rules } : Config_t.project_owner
        with Re2.Exceptions.Regex_match_failed _ -> First reviewer
      )
   |> fun (reviewers, team_reviewers) ->
+  let already_requested = List.map ~f:(fun r -> r.login) pr.requested_reviewers in
+  let already_requested_team = List.map ~f:(fun r -> r.slug) pr.requested_teams in
+  let reviewers = List.filter ~f:(not $ List.mem already_requested ~equal:String.equal) reviewers in
+  let team_reviewers = List.filter ~f:(not $ List.mem already_requested_team ~equal:String.equal) team_reviewers in
   if List.is_empty reviewers && List.is_empty team_reviewers then None else Some { reviewers; team_reviewers }