I managed to whip up a script to get the module signature of a file using Merlin’s (2.5.4 only) inference: https://gist.github.com/yawaramin/b86557ae81cbd019fcb9e071abe594de
You can use it like: sig src/foo.ml
And it will print the signature to stdout. This is useful for reading into an editor. E.g., with vim I can open a new signature file :e foo.mli and then do :r !sig % to immediately read in the signature.
I think this could be simpler if you stick to merlin 3.0 and use $ ocamlmerlin single. Haven’t tried it though.
Why don’t you use the -i option of the OCaml compiler ?
$ cat a.ml
type t = A
let v = A
let f = function A -> A
$ ocamlc -i a.ml
type t = A
val v : t
val f : t -> t
Because there’s no convenient way to pass all the necessary options in a big project. Though it’s not even that hard, you can simply peek at jbuilder’s command log and repurpose one of the commands there.
Kudos for the tip about cmitomli, it still works great with 4.06 