Core.Command.run在v0.14至v0.15间API变更？求替代方案

问题场景 #

以下代码在Core v0.14（OCaml 4.10）环境可正常编译，但在Core v0.15（OCaml 4.11）中编译失败：

open Core;;
let command = Command.basic ~summary:"essai" (
  let open Command.Let_syntax in
  let%map_open s = anon(sequence ("n" %: int))  in 
  fun () ->
    List.iter s ~f:(fun x -> Printf.printf "n = %d\n" x ) ;
  )

let () = Command.run ~version:"0.0" ~build_info:"RWO" command;;

编译报错信息 #

File "cli.ml", line 10, characters 9-20:
10 | let () = Command.run ~version:"0.0" ~build_info:"RWO" command;;
              ^^^^^^^^^^^
Error (alert deprecated): Core.Command.run
[since 2021-03] Use [Command_unix]
File "cli.ml", line 10, characters 9-20:
10 | let () = Command.run ~version:"0.0" ~build_info:"RWO" command;;
              ^^^^^^^^^^^
Error: This expression has type [ `Use_Command_unix ]
       This is not a function; it cannot be applied.

解决方案 #

Core v0.15 开始将 Unix 相关的命令行运行功能拆分到了 Command_unix 模块，原 Core.Command.run 已被废弃（不再是可调用的函数，仅作为提示标识存在）。只需做两处修改：

• 打开 Core_unix 模块（或在保留 open Core 的同时额外打开 Command_unix）
• 将 Command.run 替换为 Command_unix.run

修改后的完整代码：

open Core_unix;;
let command = Command.basic ~summary:"essai" (
  let open Command.Let_syntax in
  let%map_open s = anon(sequence ("n" %: int))  in 
  fun () ->
    List.iter s ~f:(fun x -> Printf.printf "n = %d\n" x ) ;
  )

let () = Command_unix.run ~version:"0.0" ~build_info:"RWO" command;;

若需保留 open Core，也可以这样写：

open Core;;
open Command_unix;;
let command = Command.basic ~summary:"essai" (
  let open Command.Let_syntax in
  let%map_open s = anon(sequence ("n" %: int))  in 
  fun () ->
    List.iter s ~f:(fun x -> Printf.printf "n = %d\n" x ) ;
  )

let () = run ~version:"0.0" ~build_info:"RWO" command;;

内容的提问来源于stack exchange，提问作者Pierre G.