Support Windows

[Julow]

Currently, Mdx on Windows doesn't work well:

• Line endings: Fix end of line parsing on Windows #294

• Cram blocks don't work because Mdx is calling sh.

• Calling ocaml-mdx-test doesn't work every time
  argv0 cannot be trusted, also Mdx doesn't control how its installed and shouldn't. PATH is the right abstraction here.
  In Mdx's testsuite, Dune gives us a path containing /, Windows' execve exits without warning and nothing happen.

• In Mdx's testsuite

  • dune.inc files are changed because of line encoding
  • mli unit tests are failing because of line encoding
  • mdx-test/* tests use POSIX shell features (echo, heredoc, for loops) and unix tools (ls, seq)

I'm using Mdx in Odoc's testsuite and I'd like to run tests on Windows.

[emillon]

For point 3, this is not what's happening: execvp doesn't fail silently (when it fails, it raises an exception) but it reaches a state where it's a new process so dune doesn't know about it, and its outputs are closed so it cannot print anything. #299 fixes that!

[emillon]

For cram-style tests, we expect something like a posix shell so it's ok to rely on the presence of sh and use things like echo, for loops, etc.

[Sudha247]

Hello! Bumping this.

For context; Eio tests run with mdx. We recently included a Select based backend for Windows, enabling Eio to work on Windows. This issue is a blocker for Eio 1.0. It'd be nice to fix it before ideally, so we can be reasonably sure the Windows backend works (and fix issues we might run into). Happy to help with testing or other ways we can.

cc @talex5 @polytypic

[emillon]

Hi.
I don't think that this issue is properly scoped at the moment (in the sense that we can't easily close it), but mdx works on windows. There used to be an issue with stray programs, fixed in #299. Cram tests are tricky to do in a portable way but that's not really a problem with mdx itself. md programs should work.

What's not working in the context of eio, precisely?

[polytypic]

Let me get back to this next week (vacationing this week) as I’ll try to get the Eio mdx tests working. I suspect most of the issues can be worked around.