Merge branch 'yasu/projectowners'

* yasu/projectowners:
  docs: describe draft PR behavior
  github: don't request reviews if no diff from current reviewer list
  github: request project owner review if non-draft only
  cfg: change project owner syntax to record list
  docs: + project_owners
  github: request review when pr labeled
  cfg: + project_owners
  github: derive project owners from incoming label list
  github: + request_reviewers api

Author: yasunariw

documentation/config_docs.md

@@ -23,6 +23,9 @@ Refer [here](https://docs.github.com/en/free-pro-team@latest/developers/webhooks
     },
     "status_rules": {
         ...
+    },
+    "project_owners": {
+        ...
     }
 }
 ```
@@ -33,6 +36,7 @@ Refer [here](https://docs.github.com/en/free-pro-team@latest/developers/webhooks
 | `label_rules` | label rules config object | required field |
 | `prefix_rules` | prefix rules config object | required field |
 | `status_rules` | status rules config object | all status notifications are ignored |
+| `project_owners` | project owners config object | no project owners are defined |
 
 ## Label Options
 
@@ -238,3 +242,37 @@ You can optionally provide a **status condition** to specify additional requirem
     }
 }
 ```
+
+## Project Owners
+
+In GitHub, ["code owners"](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners) are the users/teams whose review is automatically requested when a PR modifying code in a given directory is opened. **Project owners** behave similarly, with two differences.
+
+- Owners are defined _per PR label_, instead of _per directory_ (or directory pattern)
+- Definitions should be placed in the per-repo Monorobot configuration file, instead of a `CODEOWNERS` file
+
+Draft PR behavior is similar to code owners. From GitHub documentation:
+
+> Code owners are not automatically requested to review draft pull requests. [...] When you mark a draft pull request as ready for review, code owners are automatically notified.
+
+The syntax for listing users is `username`. For teams, it is `org/team-name`.
+
+Note that the owner of the personal access token cannot be a project owner, as GitHub disallows a user from self-requesting a review. Consider provisioning a separate bot user, or authenticating using a [GitHub App](https://docs.github.com/en/developers/apps/building-github-apps/authenticating-with-github-apps#accessing-api-endpoints-as-a-github-app) instead.
+
+```json
+{
+    ...,
+    "project_owners": {
+        "rules": [
+            {
+                "label": "Label 1",
+                "owners": ["user1", "user2", "org/team1"]
+            },
+            {
+                "label": "Label 2",
+                "owners": ["org/team2", "user3"]
+            }
+        ]
+    },
+    ...
+}
+```

lib/action.ml

@@ -208,6 +208,27 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
       if config_was_modified then fetch_config () else Lwt.return @@ Ok ()
     | _ -> Lwt.return @@ Ok ()
 
+  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 cfg.project_owners with
+      | Some reviewers ->
+        ( match%lwt Github_api.request_reviewers ~ctx ~repo:repository ~number ~reviewers with
+        | Ok () -> Lwt.return_unit
+        | Error e -> action_error e
+        )
+      | None -> Lwt.return_unit
+    in
+    match req with
+    | Github.Pull_request
+        { action; pull_request = { draft = false; state = Open; _ } as pull_request; repository; number; _ } ->
+      begin
+        match action with
+        | Ready_for_review | Labeled -> project_owners pull_request repository number
+        | _ -> Lwt.return_unit
+      end
+    | _ -> Lwt.return_unit
+
   let process_github_notification (ctx : Context.t) headers body =
     try%lwt
       let secrets = Context.get_secrets_exn ctx in
@@ -218,7 +239,7 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
         | Error e -> action_error e
         | Ok () ->
           let%lwt notifications = generate_notifications ctx payload in
-          let%lwt () = send_notifications ctx notifications in
+          let%lwt () = Lwt.join [ send_notifications ctx notifications; do_github_tasks ctx payload ] in
           ( match ctx.state_filepath with
           | None -> Lwt.return_unit
           | Some path ->

lib/api.ml

@@ -10,6 +10,13 @@ module type Github = sig
   val get_pull_request : ctx:Context.t -> repo:repository -> number:int -> (pull_request, string) Result.t Lwt.t
 
   val get_issue : ctx:Context.t -> repo:repository -> number:int -> (issue, string) Result.t Lwt.t
+
+  val request_reviewers
+    :  ctx:Context.t ->
+    repo:repository ->
+    number:int ->
+    reviewers:request_reviewers_req ->
+    (unit, string) Result.t Lwt.t
 end
 
 module type Slack = sig

lib/api_local.ml

@@ -22,6 +22,8 @@ module Github : Api.Github = struct
   let get_pull_request ~ctx:_ ~repo:_ ~number:_ = Lwt.return @@ Error "undefined for local setup"
 
   let get_issue ~ctx:_ ~repo:_ ~number:_ = Lwt.return @@ Error "undefined for local setup"
+
+  let request_reviewers ~ctx:_ ~repo:_ ~number:_ ~reviewers:_ = Lwt.return @@ Error "undefined for local setup"
 end
 
 module Slack_base : Api.Slack = struct

lib/api_remote.ml

@@ -51,6 +51,13 @@ module Github : Api.Github = struct
     | Ok res -> Lwt.return @@ Ok res
     | Error e -> Lwt.return @@ fmt_error "error while querying remote: %s\nfailed to get resource from %s" e url
 
+  let post_resource (ctx : Context.t) body url =
+    let secrets = Context.get_secrets_exn ctx in
+    let headers = build_headers ?token:secrets.gh_token () in
+    match%lwt http_request ~headers ~body:(`Raw ("application/json; charset=utf-8", body)) `POST url with
+    | Ok res -> Lwt.return @@ Ok res
+    | Error e -> Lwt.return @@ fmt_error "POST to %s failed : %s" url e
+
   let get_api_commit ~(ctx : Context.t) ~repo ~sha =
     let%lwt res = commits_url ~repo ~sha |> get_resource ctx in
     Lwt.return @@ Result.map res ~f:Github_j.api_commit_of_string
@@ -62,6 +69,11 @@ module Github : Api.Github = struct
   let get_issue ~(ctx : Context.t) ~repo ~number =
     let%lwt res = issues_url ~repo ~number |> get_resource ctx in
     Lwt.return @@ Result.map res ~f:Github_j.issue_of_string
+
+  let request_reviewers ~(ctx : Context.t) ~repo ~number ~reviewers =
+    let body = Github_j.string_of_request_reviewers_req reviewers in
+    let%lwt res = pulls_url ~repo ~number ^ "/requested_reviewers" |> post_resource ctx body in
+    Lwt.return @@ Result.map res ~f:(fun _ -> ())
 end
 
 module Slack : Api.Slack = struct

lib/config.atd

@@ -1,6 +1,7 @@
 type status_rule <ocaml from="Rule"> = abstract
 type prefix_rule <ocaml from="Rule"> = abstract
 type label_rule <ocaml from="Rule"> = abstract
+type project_owners_rule <ocaml from="Rule"> = abstract
 
 (* This type of rule is used for CI build notifications. *)
 type status_rules = {
@@ -22,12 +23,18 @@ type label_rules = {
   rules: label_rule list;
 }
 
+(* This type of rule is used for routing PR review requests to users. *)
+type project_owners = {
+  rules: project_owners_rule list;
+}
+
 (* This is the structure of the repository configuration file. It should be at the
    root of the monorepo, on the main branch. *)
 type config = {
   prefix_rules : prefix_rules;
   label_rules : label_rules;
   ~status_rules <ocaml default="{allowed_pipelines = Some []; rules = []}"> : status_rules;
+  ~project_owners <ocaml default="{rules = []}"> : project_owners;
   ?main_branch_name : string nullable; (* the name of the main branch; used to filter out notifications about merges of main branch into other branches *)
 }
 

lib/github.atd

@@ -269,6 +269,11 @@ type commit_comment_notification = {
   sender: github_user;
 }
 
+type request_reviewers_req = {
+  reviewers : string list;
+  team_reviewers : string list;
+}
+
 (* other generic events *)
 type event_notification = {
   repository: repository

lib/github.ml

@@ -92,7 +92,9 @@ type gh_link =
   | Issue of repository * int
   | Commit of repository * commit_hash
 
-let gh_re = Re2.create_exn {|^(.*)/(.+)/(.+)/(commit|pull|issues)/([a-z0-9]+)/?$|}
+let gh_link_re = Re2.create_exn {|^(.*)/(.+)/(.+)/(commit|pull|issues)/([a-z0-9]+)/?$|}
+
+let gh_org_team_re = Re2.create_exn {|[a-zA-Z0-9\-]+/([a-zA-Z0-9\-]+)|}
 
 (** [gh_link_of_string s] parses a URL string [s] to try to match a supported
     GitHub link type, generating repository endpoints if necessary *)
@@ -108,7 +110,7 @@ let gh_link_of_string url_str =
   match Uri.host url with
   | None -> None
   | Some host ->
-  match Re2.find_submatches_exn gh_re path with
+  match Re2.find_submatches_exn gh_link_re path with
   | [| _; prefix; Some owner; Some name; Some link_type; Some item |] ->
     let base = Option.value_map prefix ~default:host ~f:(fun p -> String.concat [ host; p ]) in
     let scheme = Uri.scheme url in
@@ -137,3 +139,19 @@ let gh_link_of_string url_str =
       with _ -> None
     end
   | _ | (exception Re2.Exceptions.Regex_match_failed _) -> None
+
+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
+         let team = Re2.find_first_exn ~sub:(`Index 1) gh_org_team_re reviewer in
+         Second team
+       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 }

lib/rule.atd

@@ -79,4 +79,13 @@ type label_rule = {
   ?allow <json name="match"> : string list nullable;
   ?ignore : string list nullable;
   channel_name <json name="channel"> : string;
-}
+}
+
+(* Requests reviews from [owners] if a PR is labeled with [label]. Owner format:
+   - users: "username"
+   - teams: "org/team"
+*)
+type project_owners_rule = {
+  label: string;
+  owners: string list;
+}

lib/rule.ml

@@ -125,3 +125,10 @@ module Label = struct
          Stdio.printf " -> #%s\n%!" rule.channel_name
        )
 end
+
+module Project_owners = struct
+  let match_rules (l : Github_t.label) ~rules =
+    match List.find rules ~f:(fun { label; _ } -> String.equal label l.name) with
+    | Some { owners = []; _ } | None -> []
+    | Some { owners; _ } -> owners
+end