## Summary
The basic idea here is: any project can either be a package, or not
("virtual").
If a project is virtual, we don't build or install it.
A project is virtual if either of the following are true:
- `tool.uv.virtual = true` is set.
- `[build-system]` is absent.
The concept of "virtual projects" only applies to workspace member right
now; it doesn't apply to `path` dependencies which are treated like
arbitrary Python source trees.
TODOs that should be resolved prior to merging:
- [ ] Documentation
- [ ] How do we reconcile this with "virtual workspace roots" which are
a little different -- they omit `[project]` entirely and don't even have
a name?
- [x] `uv init --virtual` should create a virtual project rather than a
virtual workspace.
- [x] Running `uv sync` in a virtual project after `uv init --virtual`
shows `Audited 0 packages in 0.01ms`, which is awkward. (See:
https://github.com/astral-sh/uv/pull/6588.)
Closes https://github.com/astral-sh/uv/issues/6511.
## Summary
We now respect the `environments` field in `uv pip compile --universal`,
e.g.:
```toml
[tool.uv]
environments = ["platform_system == 'Emscripten'"]
```
Closes https://github.com/astral-sh/uv/issues/6641.
For users who were using absolute paths in the `pyproject.toml`
previously, this is a behavior change: We now convert all absolute paths
in `path` entries to relative paths. Since i assume that no-one relies
on absolute path in their lockfiles - they are intended to be portable -
I'm tagging this as a bugfix.
Closes https://github.com/astral-sh/uv/pull/6438
Fixes https://github.com/astral-sh/uv/issues/6371
## Summary
The strategy here is: if the user provides supported environments, we
use those as the initial forks when resolving. As a result, we never add
or explore branches that are disjoint with the supported environments.
(If the supported environments change, we ignore the lockfile entirely,
so we don't have to worry about any interactions between supported
environments and the preference forks.)
Closes https://github.com/astral-sh/uv/issues/6184.
This already rejects `pyproject.toml`... but because the schema
validation is relaxed (we allow unknown fields, and all fields are
optional), a `pyproject.toml` doesn't get properly rejected here.
This PR makes the schema stricter, but in a safe way (by adding the
other `tool.uv` fields, like `workspace`, as any).
Closes#5832.
Resolves#4467.
## Summary
This PR implements the following
1. Add `tool.uv.constraint-dependencies` to pyproject.toml
1. Support to refer `tool.uv.constraint-dependencies` in `uv lock`
1. Support to refer `tool.uv.constraint-dependencies` in `uv pip
compile/install`
These are analogues of the override features implemented in #3839 and
#4369.
## Test Plan
Add test.
