FileWatching has issues with WSL2

[nhabedi]

This was originally a comment on an issue with Revise.jl, but Tim Holy recommended filing this as a Julia bug, so this is what I'm doing now.

It seems FileWatching has problems with WSL2. Below is what I can reproduce. The gist of it seems to be that FileWatching works within the "native" file system of WSL, but ceases to work in the normal Windows file system. (One funny thing is that it makes a slight difference if the file is modified from a WSL program - but only if you watch the directory it's in. That's the last working case below.)

julia> using FileWatching

julia> watch_file("/tmp/")
# change /tmp/foo from WSL bash
FileWatching.FileEvent(false, true, false) 

julia> watch_file("/tmp/foo")
# change /tmp/foo from WSL bash
FileWatching.FileEvent(false, true, false)

julia> watch_file("/tmp/")
# change /tmp/foo from Windows-Emacs
FileWatching.FileEvent(false, true, false) 

julia> watch_file("/tmp/foo")
# change /tmp/foo from Windows-Emacs
FileWatching.FileEvent(false, true, false)

julia> watch_file("/mnt/c/Users/edi/Desktop")
# change c:/Users/edi/Desktop/foo from WSL bash
FileWatching.FileEvent(false, true, false)

julia> watch_file("/mnt/c/Users/edi/Desktop/foo")
# change c:/Users/edi/Desktop/foo from WSL bash
# NOTHING HAPPENS

julia> watch_file("/mnt/c/Users/edi/Desktop")
# change c:/Users/edi/Desktop/foo from Windows-Emacs
# NOTHING HAPPENS

julia> watch_file("/mnt/c/Users/edi/Desktop/foo")
# change c:/Users/edi/Desktop/foo from Windows-Emacs
# NOTHING HAPPENS

julia> versioninfo()
Julia Version 1.4.2
Commit 44fa15b150* (2020-05-23 18:35 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-8.0.1 (ORCJIT, skylake)

[jks-liu]

This maybe a WSL issue, ref to microsoft/WSL#4739.

[StefanKarpinski]

It does look like an upstream bug. Thanks for the cross-link, @jks-liu!