Plugins: allow registration of multiple subcommands

compiler/driver.ml

@@ -1238,4 +1238,9 @@ module Plugin = struct
     let name = String.lowercase_ascii name in
     let info = Cmdliner.Cmd.info name ?man ?doc ~docs:Cli.s_plugins in
     Plugin.register info term
+
+  let register_subcommands name ?man ?doc cmds =
+    let name = String.lowercase_ascii name in
+    let info = Cmdliner.Cmd.info name ?man ?doc ~docs:Cli.s_plugins in
+    Plugin.register_subcommands info cmds
 end

compiler/driver.mli

@@ -119,4 +119,11 @@ module Plugin : sig
     ?doc:string ->
     (Global.options -> unit) Cmdliner.Term.t ->
     unit
+
+  val register_subcommands :
+    string ->
+    ?man:Cmdliner.Manpage.block list ->
+    ?doc:string ->
+    unit Cmdliner.Cmd.t list ->
+    unit
 end

compiler/plugin.ml

@@ -26,6 +26,10 @@ let register info term =
   Hashtbl.replace backend_plugins name
     (Cmd.v info Term.(term $ Cli.Flags.Global.options))
 
+let register_subcommands info cmds =
+  let name = String.lowercase_ascii (Cmd.name (Cmd.v info (Term.const ()))) in
+  Hashtbl.replace backend_plugins name (Cmd.group info cmds)
+
 let list () = Hashtbl.to_seq_values backend_plugins |> List.of_seq
 let names () = Hashtbl.to_seq_keys backend_plugins |> List.of_seq
 let load_failures = Hashtbl.create 17

compiler/plugin.mli

@@ -28,6 +28,13 @@ val register :
     [--plugins-dirs] to be handled correctly, and for setting debug flags), but
     can add more. *)
 
+val register_subcommands : Cmdliner.Cmd.info -> unit Cmdliner.Cmd.t list -> unit
+(** This alternative to [register] allows to register plugins that define
+    multiple subcommands (e.g. [catala myplugin subcommand --help]). Be aware
+    that all subcommands should take the [Catala_utils.Cli.Flags.Global.options]
+    term that handles the [--plugins-dirs] flags and performs some
+    initialisations. *)
+
 (** {2 catala-facing API} *)
 
 val list : unit -> t list