If you are using vscode or any other editor that supports the Language Server Protocol [1], ocaml has an excellent LSP offering [2] now that is built on top of merlin. There is a vscode plugin available as well [3].

[1] https://microsoft.github.io/language-server-protocol/

[2] https://github.com/ocaml/ocaml-lsp/

[3] https://marketplace.visualstudio.com/items?itemName=ocamllab...

Just to add to what anuragsoni said--Merlin is basically obsolete now, use the OCaml Language Server instead.

Merlin is not obsolete. OCaml-lsp depends on Merlin for one. It is also a really nice option on its own, specially for people on vim or emacs.

I find it hard to say something has been obsoleted by a tool which depends on the former to function

I did say 'basically', to not have to explain the entire architecture of the system for the benefit of newcomers. But yes, if we are being pedantic, ocamllsp internally uses merlin. To be precise, new users are directed to use ocamllsp wherever possible instead of merlin directly.

Merlin also supports renaming symbols in scope, showing the type of an expression, go-to-definition, and more. I wouldn't want to live without it.