## Summary
This PR adds support for pip's `--no-build-isolation`. When enabled,
build requirements won't be installed during PEP 517-style builds, but
the source environment _will_ be used when executing the build steps
themselves.
Closes https://github.com/astral-sh/uv/issues/1715.
## Summary
This PR migrates our virtualenv creation from a setup that assumes prior
knowledge of the correct paths, to a technique borrowed from
`virtualenv` whereby we use `sysconfig` and `distutils` to determine the
paths. The general trick is to grab the expected paths with `sysconfig`,
then make them all relative, then make them absolute for a given
directory.
Closes#2095.
Closes#2153.
## Summary
This will make it easier to use the paths returned by `distutils.py`
(for some cases). No code or behavior changes; just removing some fields
we don't need.
## Summary
After https://github.com/astral-sh/uv/pull/2121, the only remaining
issue is that calling `canonicalize` on these Pythons returns an error.
Closes https://github.com/astral-sh/uv/issues/2105.
## Test Plan
Uninstalled all python.org Pythons on my Windows machine, then created a
virtualenv. The resulting config file:
```
Using Python 3.11.8 interpreter at: C:\Users\crmar\AppData\Local\Microsoft\WindowsApps\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\python.exe
Creating virtualenv at: .venv
Activate with: .venv\Scripts\activate
PS C:\Users\crmar\workspace\puffin> cat .\.venv\pyvenv.cfg
home = C:\Users\crmar\AppData\Local\Microsoft\WindowsApps\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0
implementation = CPython
version_info = 3.11.8
include-system-site-packages = false
uv = 0.1.13
prompt = puffin
```
Prior to this PR, it would fail with a canonicalization error.
Prior to #2121, it would leave a "bad" Python in the config file:
```
Using Python 3.11.8 interpreter at: C:\Users\crmar\AppData\Local\Microsoft\WindowsApps\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\python.exe
Creating virtualenv at: .venv
Activate with: .venv\Scripts\activate
PS C:\Users\crmar\workspace\puffin> cat .\.venv\pyvenv.cfg
home = C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2288.0_x64__qbz5n2kfra8p0
implementation = CPython
version_info = 3.11.8
include-system-site-packages = false
uv = 0.1.13
prompt = puffin
```
Which, once activated, would fail with:
```
(venv) PS C:\Users\crmar\workspace\puffin> python
No Python at '"C:\Users\crmar\AppData\Local\Programs\Python\Python312\python.exe'
```
## Summary
When I install via the Windows Store, `interpreter.base_prefix` contains
a bunch of resolved information that leads to a broken environment.
Instead, we now use `sys._base_executable` on Windows by default,
falling back to `sys.base_prefix` if it doesn't exist. (There are some
issues with `sys.base_executable` that lead to complexity in
`virtualenv`, but they only affect POSIX.) Admittedly, I don't know when
`sys._base_executable` wouldn't exist. It exists in all the environments
I've tested.
Additionally, we use the system interpreter directly if we're outside of
a virtualenv.
## Summary
It looks like these have been included since the very first gourgeist
commit, but `virtualenv` and `venv` don't include them, and they only
add complexity AFAICT.
## Summary
I think Camino is nice but it makes it much harder to work in
`uv-virtualenv`, since it's the _only_ crate that uses it. If we want to
use Camino, we should use it everywhere IMO.
