maybe this can help? https://blog.pantsbuild.org/multiple-lockfiles-python/

hmm but that requires us to maintain an additional lock file, seems a bit distruptive as we only use poetry.lock files

unless it's compatible with poetry lock. I guess we can say

[resolves]
new-project = "src/python/new-project/poetry.lock"

then the monolith will just use default resolves and not get conflicted?

if we have visibility rules, the monoliuth and this project would be restricted on cross dependencies

And in 2.16 I added a feature that resolves ambiguity in dep inference by source root

Which I think is exactly what you need here

Well, actually, maybe you don't even need that

if your new project declares that it uses "resolve2" then dep inference will use that

with no additional configuration

any changes to new-project should not impact the monolith

So trying the following:

enable_resolves = true
resolves = """
{
  "monolith": "poetry.lock",
  "test-selection": "src/python/test-selection-api/poetry.lock"
}
"""

seeing this conflict:

11:09:22.51 [WARN] The target app/monolith/something.py imports `psycopg2`, but Pants cannot safely infer a dependency because more than one target owns this module, so it is ambiguous which to use: ['//:poetry#psycopg2-binary', 'src/python/test-selection-api:poetry#psycopg2'].

Please explicitly include the dependency you want in the `dependencies` field of app/monolith/something.py, or ignore the ones you do not want by prefixing with `!` or `!!` so that one or no targets are left.

Alternatively, you can remove the ambiguity by deleting/changing some of the targets so that only 1 target owns this module. Refer to <https://www.pantsbuild.org/v2.14/docs/troubleshooting#import-errors-and-missing-dependencies>.
11:09:22.51 [WARN] The target app/monolith/something.py imports `psycopg2`, but Pants cannot safely infer a dependency because more than one target owns this module, so it is ambiguous which to use: ['//:poetry#psycopg2-binary', 'src/python/test-selection-api:poetry#psycopg2'].

monolith has the following build defaults:

__defaults__(all=dict(resolve="monolith"))

okay think I got it working

I did the following: 1. Enable resolves for the project

[python]
enable_resolves = true
resolves = """
{
  "python-default": "default.lock",
  "test-selection": "src/python/test-selection/test-selection.lock"
}
"""

I added both

python-default

and

test-selection

. The first

python-default

is a place holder to make pants happy (since the default "3rdparty/python/default.lock" does not exists anyway, it shouldn't matter) 2. Set the build defaults for the test-selection project to use

test-selection

resolves This is important because you must mark

poetry_requirements

to their correct resolve. For example

poetry_requirements(
    name="poetry",
    resolve="test-selection"
)

This is important to do priori to generating the resolve lock. 3. Generate a lock file for the new project

./pants generate-lockfiles --resolve=test-selection

After doing all the above, the monolith can now infer dependencies as it did before. This means we can work on a new project without impact the monolith

now I'm curious if step 3 is even necessary

maybe a good thing to do for performance of pants runs in CI but it seems like it's not really necessary to get it working. it is necessary for new-project but not necessary for the monolith default

You have a poetry lockfile for one resolve and a pex lockfile for the other, but that's fine