#18532 Allow Python tools to isntall from a different resolve/lockfile per-process, instead of a global static resolve Issue created by danxmoran Is your feature request related to a problem? Please describe. While testing out the new

install_from_resolve

feature in Pants 2.16, I ran into a situation where: •

pytest

depends on

attrs

• Resolve A pins

attrs==21.4

• Resolve B pins

attrs==22.2

When we set

[pytest].install_from_resolve = "A"

in

pants.toml

, the

pytest

Pex installed from the lockfile uses

attrs==21.4

. This works perfectly when testing code in resolve

A

, but we hit exceptions when running tests in resolve

B

because some code uses features that were only introduced in `v22`+ of

attrs

. Though we specifically hit this problem with

pytest

, I can imagine the same thing happening for any Python tool with transitive dependencies that overlap those of user resolves. Describe the solution you'd like Instead of statically specifying one resolve in

install_from_resolve

, it would be nice if we could configure some marker value like:

[pytest]
install_from_resolve = "__magic_placeholder__"

When

__magic_placeholder__

is set (or some other less-magic config is set), Pants would dynamically select the resolve/lockfile to install tools from, so that the tool resolve always matches the resolve of the covered code. i.e.: • When running

pytest

over code in resolve A, install

pytest

out of the lockfile for resolve A • When running

pytest

over code in resolve B, install

pytest

out of the lockfile for resolve B • Etc. for other Python tools that install out of a lockfile This would enable cases like the above, where it's possible to satisfy the requirement constraints of a tool (

pytest

) in any one user resolve, but not possible to satisfy the constraints of every user resolve simultaneously. Describe alternatives you've considered In our specific case we should be able to upgrade

attrs

in resolve A to get un-stuck. But I worry about repeatedly bumping into this problem as we bump dependency versions down the road. pantsbuild/pants