Hello all,
I would like to build an interface for plugins that allow to extract at the
same time a very specific data for a plugin family and to extract
general help for plugins.
Here is an example:
(** All the plugins I want to manage *)
type plugin_kind = [`Build | `Install]
(** Generic plugin *)
type 'a plugin = 'a * string
(** Help data for all plugin *)
module MapPlugin =
Map.Make
(struct
type t = plugin_kind plugin
let compare = compare
end)
let all_help: string MapPlugin.t ref =
ref MapPlugin.empty
let help plg =
MapPlugin.find plg !all_help
(** Functor to build function related to one type of plugin *)
module type PLUGIN_FAMILY =
sig
type act
type kind
val kind_default: kind
end
module Make (F: PLUGIN_FAMILY) =
struct
module MapPluginSelf =
Map.Make
(struct
type t = F.kind plugin
let compare = compare
end)
let all_act: F.act MapPluginSelf.t ref =
ref MapPluginSelf.empty
let act (plg : F.kind plugin) =
MapPluginSelf.find plg !all_act
let create name help act =
let id =
F.kind_default, name
in
all_help := MapPlugin.add id help !all_help;
all_act := MapPlugin.add id act !all_act;
id
end
(** Functions for build plugins *)
module Build =
Make
(struct
type act = unit -> unit
type kind = [`Build]
let default = `Build
end)
(** Functions for install plugins *)
module Install =
Make
(struct
type act = string list -> unit
type kind = [`Install]
let default = `Install
end)
type package =
{
name: string;
plugin_build: [`Build] plugin;
plugin_install: [`Install] plugin;
}
let run pkg =
prerr_endline (help pkg.plugin_build);
prerr_endline (help pkg.plugin_install);
(Build.act pkg.plugin_build) ();
(Install.act pkg.plugin_install) ()
This code doesn't compile because I see no way to explain that F.kind is
included into plugin_kind.
Here is the precise error:
camlc -o test test.ml
File "test.ml", line 51, characters 32-34:
Error: This expression has type F.kind * 'a
but an expression was expected of type
MapPlugin.key = plugin_kind * string
Type F.kind is not compatible with type
plugin_kind = [ `Build | `Install ]
make: *** [all] Erreur 2
Does anyone know a good solution to this problem? Does anyone have a
better solution to this problem? (different design?)
Thank you for your answers,
Sylvain Le Gall
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