#477 seems to have broken cargo doc-based documentation previews

[davidbarsky]

Hello! The (extremely welcome!) changes in #477 appears to have broken our (relatively niche) use-case where we generate documentation previews for each PR send to tokio-rs/tracing. I suspect that with the deployment of #447, the target directory that's generated by Cargo is no longer available to publish step. This is problematic for us as we use contents of target/doc as the deployable documentation preview. In my attempts to debug the deployment failures we're seeing (tokio-rs/tracing#1130), I've developed the following theory:

1. The cache_cwd_directory function (callsite, definition) moves Cargo's build output to $NETLIFY_CACHE_DIR.
2. cache_cwd_directory calls move_cache, which removes the Cargo-generated target directory.

Contemporaneously with #477 (comment) being posted, we've started noticing the site build errors contain the message "Deploy directory 'target/doc' does not exist". Here's the first build where I've noticed this: https://app.netlify.com/teams/tokio/builds/5fd051070a10d60007567df3.

Anyways, thanks so much for this service! I'm pretty sure this is the first we've ever had to reach out for support!

[mraerino]

this is unfortunate, i'm sorry. we actually have a special flag enabled internally which moves caching after the upload step so we didn't see it for ourselves.

for now the workaround will be to manually copy the docs outside of target, but i'll try to get a fix in so that we don't move those files.

[cecton]

If you are on a filesystem that supports it you can use CoW instead of move:

# copy super fast
cp --reflink=always source/ destination/

https://www.man7.org/linux/man-pages/man1/cp.1.html

It will be as fast as the move you do but it copies instead so both stay accessible.

cc @mraerino