## Summary
When we unzip wheels in the cache, we write the directories out to an
`archive-v0` bucket, and then symlink into that bucket from the
`wheels-v0` and `built-wheels-v0` buckets.
On Windows, symlinks are not well supported. Specifically, they need to
be explicitly enabled by the user. So, instead of symlinks, we now use
junctions, which are well-supported on Windows, and allow you to
(effectively) symlink a directory to another directory. This PR
implements said junction support, which gets the core installer working
on Windows.
In the past, we also used symlinks to implement another primitive: we
wanted to be able to replace a directory "atomically" (I put
"atomically" in quotes because I don't know if it's actually a
guaranteed atomic operation), in case someone was trying to use the
directory while we were replacing it (as opposed to deleting the
directory, then moving it into place).
On Windows, it doesn't appear to be possible to atomically replace a
junction. So instead, I'm using a new design, whereby the cache always
returns canonicalized paths. We know these canonicalized paths are
unique and won't be replaced, so they're safe for writers to rely on. In
general, when we write new data to the cache, we now return the
canonicalized path. When we read from the cache, and try to identify
(e.g.) the set of wheels available to us, we canonicalize the links
immediately and consider them non-existent if that operation fails.
Closes#1085.
---------
Co-authored-by: konstin <konstin@mailbox.org>
## Summary
This PR enables `puffin clean` to accept package names as command line
arguments, and selectively purge entries from the cache tied to the
given package.
Relate to #572.
## Test Plan
Modified all the caching tests to run an additional step to (1) purge
the cache, and (2) re-install the package.
This PR modifies the source distribution building to replace any
existing targets after building the new wheel. In some cases, the
existence of an existing target may be indicative of a bug, so we warn.
It's partially a workaround for some (but not all) of the errors in
https://github.com/astral-sh/puffin/issues/554.
Charlie Marsh