While banging my head against the wall trying to understand the Dune build system used with OCaml and the Melange project to compile ReasonML and Rescript to js, I came across these great simple videos by @TheEduardoRFS.
Most of below is from his hello intro. Thanks, Eduardo! Checkout his great videos at https://www.youtube.com/c/EduardoRFS.
You don't actually need this for Rescript but this gets you all the extra latest OCaml juice in the editor plus a whole lot more.
Brief
The following is a brief introduction on how to start coding in the mess that is the OCaml ecosystem.
You can call me Eduardo and I will be helping you to setup an OCaml environment ... TODO: joke with trying
Introduction??
What will you need?
To do that, you will need a couple of tools, they're. The OCaml compiler. A build system. And a language server for VSCode, because no one deserves to code without autocomplete. Everything can be installed through a package manager, so you just get the package manager and that should be it.
For this video we will be using esy, an "easy" package manager for OCaml, mostly because it simplifies the life of Windows users a lot.
Windows Warning
Warning, if you're using windows, I'm sorry for you. Ok, seriously, if you're using windows everything here must be executed as admin, because "windows bad", to run VSCode as admin you need to close all VSCode windows and execute it as admin.
Installing esy
To install esy, you're going to need the node package manager and git installed. If you have both, you can just put
npm install --global esy
on your terminal.t should take a couple of seconds. But that's it.
Install project
After that you can just clone my example project on github,
git clone https://github.com/idkjs/coding-ocaml-js-node.git
Enter the folder /hello
cd hello
And call esy
esy
The first time running esy it will install everything that we need, so it will take a couple of minutes, but on subsequent executions everything is cached, so it should be quite fast. On windows it may take a long time and you need to run your VSCode and terminal as an admin.
Add a rule with an alias to the dune file to watch the JavaScript output, note the call to node. I just took a shot in the dark and it worked. I don't know if there are docs on this:
(rule
(alias run_hello_js)
(deps Hello.bs.js)
(action
(run node ./Hello.bs.js)))
Add a script to esy to watch the js output
"watch-js": "esy b dune build @run_hello_js -w",
To check if everything is working, you can call
esy watch-js
If you see Tu tu ru~ Mayushii desu!, that means everything is working and we can now setup VSCode.
Works for ReasonML, Rescript and OCaml
Run esy hello-reason and esy hello-rescript
> esy hello-reason
Hello, Reason!
> esy hello-rescript
Hello, Rescript!
VSCode
You should go to your VSCode and install the extension "OCaml Platform". That's it, now you can open the example project on VSCode, open the file Hello.ml and you should have everything working, autocomplete, types when you hover some identifier and in-editor typechecking.
Ending
Yeah, now you can play with OCaml, like a prefessional. If you have any question send a comment below, something something like and subscribe.
Redemon File Watcher
This example use the redemon file watcher.
Add redemon
opam pin add redemon https://github.com/ulrikstrid/redemon
Try the example from the docs.
Run the following them change index.js or create a file and you should see Hello World! in the terminal.
redemon --path=./foo echo "Hello World!"
Hello World!
# after a change
Hello World!
Or pass node index.js as a command and see the output
redemon --path=./foo node foo/index.js
hello
# after editing text
hello again
Hope this helps!
Top comments (0)