Previously, when installing a package we would delete the target
directory before copying (or linking) the contents of the package.
However, this means that we do not properly support namespace packages
which can share a target directory. Instead the last package to be
installed would be override existing packages. Since we install packages
in parallel, this could result in a race condition where the target
directory already exists which is not allowed when using `clonefile`.
See example error in #515.
https://github.com/astral-sh/puffin/pull/516/commits/c7e63d2dcebab6aa37427c58a9db7603db546a4f
provides a regression test for this — it fails on `main`.
Here, we implement a recursive merge when the target directory already
exists. Both packages will be installed into the same directory. We no
longer delete the target directory, which seems okay since we uninstall
packages before installing now.
When files conflict, we will likely throw an error still. The correct
behavior to implement in this case is unclear, as if we just take "first
write wins" or "last write wins" we could end up with some files from
one package and some from another resulting in two broken packages. A
possible solution here is to lock the target directories while copying.
Zanie Blue
5f1f207628