[danielgafni]

What

A new pyproject module: the shared discovery layer for our Python modules (uv, ruff, deptry, and later pytest/pyrefly). It runs no tools itself and exposes two collections:

• projects: every directory holding a pyproject.toml. Fields: name, workspace (the workspace that installs it as a member), nested, local_dependencies. Functions: source(ws), pyproject(ws).
• workspaces: every directory holding a workspace marker, uv.lock and pylock.toml by default (configurable with the workspaceMarkers setting). Fields: lockfiles, members, local_dependencies. Functions: projects(), source(ws), manifests(ws).

Both are keyed by path relative to the workspace root and take an exclude glob setting.

Why

These fix problems found in dagger/python's shared pyproject library and in our own modules:

Problem	Here
Path deps and members outside the project dir (../lib) aren't mounted, so uv sync breaks	source loads the project's tree plus its transitive path/workspace sources, wherever they live
A monorepo root's source carries every nested project	Every file belongs to the deepest project containing it; nested projects nothing needs are excluded, including fixtures nested inside a member
Regex TOML parsing misses dotted keys, quoting and marker-split sources	tomllib
Scope globs silently match nothing	pathlib full_match; ** crosses directories, and a trailing /** also matches the directory itself
The dependency layer is invalidated by unrelated edits	workspace.manifests(ws) holds only resolver inputs (markers, uv.toml, members' and local deps' pyproject.toml/.python-version)
Whole-repo Directory input: any edit busts everything	The Workspace API with per-item include/exclude loads

uv semantics come from pyproject.toml, the same source uv itself uses, not the lockfile:

• Membership follows [tool.uv.workspace] members/exclude, and the deepest workspace wins.
• Members inherit the root's [tool.uv.sources], overridden per package.
• { workspace = true } resolves by normalized name.
• Missing path sources load nothing instead of failing (the partial-workspace case).