Update opam installation versions

[jdlehman]

The opam installation versions are locked to older versions of merlin and reason. Is there a reason these are locked at these versions or have they just been missed in doc updates?

Removing the version constraints will install the latest, which should be the desired case for most users and will have the added benefit of not needing to update this file for version changes

[zploskey]

The instructions should at the very least be updated to reason 3.0.0. I'm not sure if there is any particular reason that merlin 3 won't work, but I noticed that reason-cli still ships 2.5.4.

[jdlehman]

Agreed. 3.0.0 isn't in opam yet last I checked, but I am happy to make the change if we want to be specific (and update the merlin version if there is a reason v3 doesn't work).

[zploskey]

I think it makes sense to change it now, even before 3.0 is approved in OPAM, because none of the syntax examples will work unless Reason 3 is installed. Depending how long we expect that to take, it might be worth adding a note that it isn't there yet. Hopefully it is approved quickly.

[jordwalke]

Reason version 3.0.0 is in opam now, so that's a good change. I think we should hold off on bumping the merlin version until we know that the most recent version of merlin can work well with bucklescript. If someone can confirm, we can also bump the version of merlin here - otherwise it would be asking for an unstable dev setup to encourage it. I'll check and get back to you (or you can just bump the reason version and I'll accept asap).

[yawaramin]

Also I'd suggest to provide all OPAM package names in a single install command to help it do better resolution and minimise recompilation. I think this is a best practice in OPAM, see e.g. https://discuss.ocaml.org/t/why-does-opam-recompile-so-much/483/6?u=yawaramin

So, opam install reason merlin

[jdlehman]

I updated the versions to be hard coded, but I kept the merlin version at 2.5.4 for now. So this should be good to merge.

Based on the merlin changelog, it looks like the most notable change in 3.0.3 is Windows support, which might mean that Windows users no longer need to use Windows Subsystem for Linux (WSL). merlin 3.0.3 works locally for me on OSX with reason/bucklescript, but I do not have a Windows machine so I was not able to confirm the Windows support.

If we can get confirmation around Windows support we might be able to make a lot of improvements to docs for Windows users (especially improving the current installation process) in subsequent PRs 😄

[chenglou]

We'll verify merlin soon, thanks!

[superherointj]

Merlin 3.0.3 is not working on Windows. Only 2.5.4 works. Cause is unknown.