generating css from stylus fails on Windows

[budziq]

Hi,

I wanted to test my code fixing https://github.com/azerupi/mdBook/issues/293
And when testing the solution on Windows I have noticed that
cargo build --features=regenerate-css will always fail (with or without my changes).
It looks like Rust Command PATH finding is is broken rust-lang/rust#37519 or at least works differently than expected.

Namely stylus is represented on Windows as stylus.cmd while Command::spawn will append ".exe" but does not test with other executable extensions like cmd, thus Command::new("stylus") will expand to Command::new("stylus.exe") instead of Command::new("stylus.cmd"). Fortunately explicitly stating .

This should be relatively easy to workaround with #[cfg(windows)]
Nevertheless, the CI probably should be updated to test if stylus works too.

[azerupi]

Thank you for the report.
As I have no Windows machine, support for it is sometimes lagging a little behind. I rely very strongly on AppVeyor, and contributions from Windows users for that part.

Nevertheless, the CI probably should be updated to test if stylus works too.

Indeed, we could add the build script to the CI to assure it always works.