Questions about updating code using Command library

[basus]

I’ve been updating one of my projects to the latest version of Core (v0.12.3) and it seems like the Command module has undergone a lot of changes. I have some questions about how to do things I used to with the older Command with the current version. I have been using the current development version of Real World OCaml as a guide.

1. It seems there is no longer a file type for command arguments. RWO says that there should be a file type as part of Command.Let_syntax but I get an unbound value file error. I can’t find a file type in the documentation either.

2. Previously I could define a specification to be common to all commands (for example, debug and verbose output flags) and then use the +> combinator to include it in all other specifications. I can’t figure out how to do this with the current version.

Thanks!

[bcc32]

@basus

• It seems there is no longer a file type for command arguments. RWO says that there should be a file type as part of Command.Let_syntax but I get an unbound value file error. I can’t find a file type in the documentation either.

file has been renamed Filename.arg_type. A number of such built-in arg types have been moved to their respective modules.

@basus

2. Previously I could define a specification to be common to all commands (for example, debug and verbose output flags) and then use the +> combinator to include it in all other specifications. I can’t figure out how to do this with the current version.

You can still do this. I can think of two common ways:

1. Define a “config” parameter that includes all of the common specifications:

module Config = struct
  type t = { verbose : bool; debug : bool }

  let param =
    let open Command.Let_syntax in
    let%map_open verbose = flag "-verbose" no_arg ~doc:" verbose"
    and debug = flag "-debug" no_arg ~doc:" debug" in
    { verbose; debug }
end

(* later *)

let _ =
  Command.basic ~summary:"some command"
    (let%map_open.Command.Let_syntax config = Config.param in
     (* do something according to config *))

2. Define a parameter that imperatively sets some global options. See Async.Log.Global.set_level_via_param for an example.

[XVilka]

Worth opening a bug in RWO for that.

[jjb]

@basus

Previously I could define a specification to be common to all commands (for example, debug and verbose output flags) and then use the +> combinator to include it in all other specifications. I can’t figure out how to do this with the current version.

I’m not sure just what you want to do, but some amount of that sort of thing is done with the current Command api here.

[basus]

Thanks, I used @bcc32’s suggestion and updated my code accordingly. I also filed a bug on the Real World OCaml Github tracker about changing the use of the file type.