OCaml Weekly News

For example, you can easily print a process's stderr if it exits non-zero:

open Feather;;
let stderr, status =
  process "ls" [ "/tmp/does-not-exist" ] |> collect stderr_and_status
in
if status <> 0 then failwith ("ls failed with stderr:\n" ^ stderr)

where the types are

val process : string -> string list -> cmd

type 'a what_to_collect
val stderr_and_status : (string * int) what_to_collect

val collect :
  ?cwd:string ->
  ?env:(string * string) ->
  'a what_to_collect ->
  cmd ->
  'a

as you can imagine, we expose several of these what_to_collect's. Here's the full set:

val stdout : string what_to_collect
val stderr : string what_to_collect
val status : int what_to_collect

val stdout_and_stderr : (string * string) what_to_collect
val stdout_and_status : (string * int) what_to_collect
val stderr_and_status : (string * int) what_to_collect

type everything = { stdout : string; stderr : string; status : int }
val everything : everything what_to_collect

We considered different design approaches here. I think what we landed on keeps the call site readable and the types of the interface simple.

It should be noted: the simplest way to run a command without collecting anything is to use Feather.run.

Starting with Feather 0.1.0, you were able to start processes in the background, but the only way to wait for them to complete was to use Feather's async wrapper. For those wanting an async-less, direct-style interface, we now expose new methods to do this properly:

type 'a background_process

val run_in_background :
  ?⁠cwd:string ->
  ?⁠env:(string * string) Base.list ->
  cmd ->
  unit background_process

val collect_in_background :
  ?cwd:string ->
  ?env:(string * string) list ->
  'a what_to_collect ->
  cmd ->
  'a background_process

val wait : 'a background_process -> 'a
val wait_all : unit -> unit

where an example use might be

let server_process =
   process "my-server.exe" [] |> collect_in_background stdout_and_status
in
... do other things ...
match Feather.wait server_process with
| (stdout, 0) -> ...
| (_, 1) -> ...

Thanks again to @Firobe and @tmarti2 for their contributions to this release! I think we've made a lot of progress here and I'm excited to see where things go :slight_smile:

• new! [for GopCaml-mode-Merlin] Robustness to ill-formated syntax
  • Vendored a copy of Merlin to reuse its parser and thereby gain it's robustness to invalid syntax.
• new! Added support for customisable verbosity
  • Customise the Emacs variable `gopcaml-messaging-level` to change the level of messages that are output by GopCaml. Set it to `'none` to disable messages entirely.
• new! Fixed bug when starting zipper mode at the start of a file.
  • Zipper mode selects the immediately prior byte position to avoid inconsistencies when the cursor is just on the edge of an expression, but when the cursor is at position 1, this causes an error as 0 is not a valid point.
• new! Special casing of shebangs
  • Added support for handling shebangs at the start of a buffer.
  • Implemented as part of a larger library for preprocessing buffertext before running the parser on it - could be extended to support additional preprocessing in the future.
  • Another possible direction for extension is to use an Emacs callback to modify the text, although this may not be ideal, as the parsing has to be as fast as possible.

Its as easy as 1, 2, 3!

1. Install from opam (either `gopcaml-mode` xor `gopcaml-mode-merlin`):

   opam install gopcaml-mode
   

   or

   opam install gopcaml-mode-merlin
   

2. Compile your emacs with support for dynamic modules

3. Load gopcaml-mode in your init.el:

   (let ((opam-share (ignore-errors (car (process-lines "opam" "var" "share")))))
       (when (and opam-share (file-directory-p opam-share))
         ;; Register Gopcaml mode
         (add-to-list 'load-path (expand-file-name "emacs/site-lisp" opam-share))
           (autoload 'gopcaml-mode "gopcaml-mode" nil t nil)
           (autoload 'tuareg-mode "tuareg" nil t nil)
           (autoload 'merlin-mode "merlin" "Merlin mode" t)
         ;; Automatically start it in OCaml buffers
         (setq auto-mode-alist
         (append '(("\\.ml[ily]?$" . gopcaml-mode)
             ("\\.topml$" . gopcaml-mode))
           auto-mode-alist))
         ))
   

See the release post for version 0.0.1 for detailed instructions on how you can install it.

• Github: GitHub - Gopiandcode/gopcaml-mode: [MIRROR] Ultimate Ocaml Editing Mode
• Gitlab: Kiran Gopinathan / gopcaml-mode · GitLab