Supporting Windows (Diskuv OCaml) distribution

[jonahbeckford]

On Windows the plugin defaults to requiring ocaml.useOcamlEnv.

The Diskuv OCaml (DKML) distribution for Windows does not need wrappers. It works with the OCaml VSCode plugin as-is, and the plug-in doesn't see any switches when ocaml.useOCamlEnv is on.

But I'm needing to tell new users to disable the ocamlenv setting. What do you suggest we do for Windows users?

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Nitty gritty details if it helps:

• The DKML installer places opam and dune, among other programs, in the Windows user PATH.
• Most opam and dune commands work just the same as on Unix (except they may report Windows paths like C:\a\b\c or mixed paths like C:/a/b/c).
• Uses Opam 2.1.2 with patches to use the default OPAMROOT for Opam 2.2+. That is <LOCALAPPDATA>\opam rather than <USERPROFILE>\.opam (?) or whatever the OPAMROOT was. This different OPAMROOT used to be a problem with the plugin, but I suspect the plugin now does opam var root so the Opam 2.2+ OPAMROOT works. Confer: https://github.com/ocaml/opam/pull/4815
• There will always be a file $env:LOCALAPPDATA\Programs\DiskuvOCaml\dkmlvars-v2.sexp on Windows, or $XDG_DATA_HOME/diskuv-ocaml/dkmlvars-v2.sexp or $HOME/.local/share/diskuv-ocaml/dkmlvars-v2.sexp if XDG_DATA_HOME not defined on Unix (there will be a version for macOS coming soon). I don't think you'll need it, but I'll describe it just in case. It looks like:

(
  ("DiskuvOCamlVarsVersion" ("2"))
  ("DiskuvOCamlHome" ("C:\\Users\\beckf\\AppData\\Local\\Programs\\DISKUV~1\\0"))
  ("DiskuvOCamlBinaryPaths" ("C:\\Users\\beckf\\AppData\\Local\\Programs\\DISKUV~1\\0\\usr\\bin" "C:\\Users\\beckf\\AppData\\Local\\Programs\\DISKUV~1\\0\\bin"))
  ("DiskuvOCamlMSYS2Dir" ("C:\\Users\\beckf\\AppData\\Local\\Programs\\DISKUV~1\\tools\\MSYS2"))
  ("DiskuvOCamlDeploymentId" ("v-0.4.0-prerel91;ocaml-4.12.1;opam-2.2.0~alpha~dev;inotify-36d18f3dfe042b21d7136a1479f08f0d8e30e2f9;msys2-999CED2C8F5FF6A2;docker-B01818D2C9F9286A;pkgs-E9B3EA78336D2491;bins-E81FF8D69425188D;stubs-4E6958B274EAB043;toplevels-80941AA1C64DA259"))
  ("DiskuvOCamlVersion" ("0.4.0-prerel91"))
)

[mnxn]

I think the most elegant solution would be to check if ocaml-env exists before using it. A PATH check could done inside this branch: https://github.com/ocamllabs/vscode-ocaml-platform/blob/5d33e8a8e2b1475296d0c971a19885987ce09d11/src/ocaml_windows.ml#L10-L11

Since Diskuv OCaml doesn't have ocaml-env, the extension will use the Windows executables unless OCaml for Windows is installed. If a user has both OCaml for Windows and Diskuv OCaml, the ocaml.useOcamlEnv setting can be used to decided which is used:

• OCaml for Windows is used when useOcamlEnv is true.
• Diskuv OCaml is used when useOCamlEnv is false.

[jonahbeckford]

That is perfect! Thanks for the quick turnaround. I'll see about testing the PR.