Filter discovered Python executables by source before querying

[zanieb]

Closes #11138

Though I think we could still have a better error message there.

[zanieb]

This is a filter_ok in #11145

[charliermarsh]

Is this doing more work than before, since we're returning all the iterators here?

[zanieb]

Uhh maybe. I'd have to squint at it a bit.

Generally, it's much less work. This is pre-query (and querying is the slow part) and EnvironmentPreference::ExplicitSystem is the common case so more aggressive filtering here should be better.

It seems possible with EnvironmentPreference::OnlyVirtual we now traverse the PATH directories whereas previously we did not? I'll check on that — because I agree that's not ideal. I'd be sad about doing both this filtering and the previous match statement though, they overlap significantly.

[zanieb]

Yes you're correct, this now scans more in the OnlyVirtual case. However... we only construct that case in uv-dev (and tests)

uv/crates/uv-dev/src/compile.rs

Line 26 in 41cd4be

EnvironmentPreference::OnlyVirtual,

which was surprising to me. We basically always use this constructor

uv/crates/uv-python/src/discovery.rs

Lines 1616 to 1627 in e26affd

	impl EnvironmentPreference {
	pub fn from_system_flag(system: bool, mutable: bool) -> Self {
	match (system, mutable) {
	// When the system flag is provided, ignore virtual environments.
	(true, _) => Self::OnlySystem,
	// For mutable operations, only allow discovery of the system with explicit selection.
	(false, true) => Self::ExplicitSystem,
	// For immutable operations, we allow discovery of the system environment
	(false, false) => Self::Any,
	}
	}
	}

[zanieb]

The other case is that we'll now also perform the scanning for executables from virtual environments if you provide --system, though we'll toss those out. Might be worth changing still.

[zanieb]

e.g.

main

❯ uv python find -v --system
DEBUG uv 0.5.26+6 (ca5b84027 2025-01-31)
DEBUG Found project root: `/Users/zb/workspace/uv`
DEBUG Project `uv` is marked as unmanaged
DEBUG Reading Python requests from version file at `/Users/zb/workspace/uv/.python-version`
DEBUG Using Python request `3.12` from version file at `.python-version`
DEBUG Searching for Python 3.12 in managed installations or search path
DEBUG Searching for managed installations at `/Users/zb/.local/share/uv/python`
DEBUG Skipping incompatible managed installation `cpython-3.14.0a4-macos-aarch64-none`
DEBUG Skipping incompatible managed installation `cpython-3.10.16-macos-aarch64-none`
DEBUG Skipping incompatible managed installation `cpython-3.10.5-macos-aarch64-none`
DEBUG Found `cpython-3.12.8-macos-aarch64-none` at `/opt/homebrew/bin/python3.12` (search path)
/opt/homebrew/opt/[email protected]/bin/python3.12

vs branch

❯ uv python find -v --system
DEBUG uv 0.5.26+7 (9aefd76b4 2025-01-31)
DEBUG Found project root: `/Users/zb/workspace/uv`
DEBUG Project `uv` is marked as unmanaged
DEBUG Reading Python requests from version file at `/Users/zb/workspace/uv/.python-version`
DEBUG Using Python request `3.12` from version file at `.python-version`
DEBUG Searching for Python 3.12 in managed installations or search path
DEBUG Ignoring Python interpreter at `/Users/zb/workspace/uv/.venv/bin/python3`: system interpreter required
DEBUG Searching for managed installations at `/Users/zb/.local/share/uv/python`
DEBUG Skipping incompatible managed installation `cpython-3.14.0a4-macos-aarch64-none`
DEBUG Skipping incompatible managed installation `cpython-3.10.16-macos-aarch64-none`
DEBUG Skipping incompatible managed installation `cpython-3.10.5-macos-aarch64-none`
DEBUG Found `cpython-3.12.8-macos-aarch64-none` at `/opt/homebrew/bin/python3.12` (search path)
/opt/homebrew/opt/[email protected]/bin/python3.12

[zanieb]

Thanks for flagging 02e72be