Hi Pants team 👋 I’m evaluating Pants for a python monorepo and having an issue with 3rd party dependencies. To be honest, I’m probably having some newbie python dependency issue, but it reflects with:

./pants dependencies ::

Discover all the relevant dependencies, however

./pants dependencies path_to_a_specific_test.py

Doesn’t “find” all the relevant dependencies in the test file, failing it accordingly for a ModuleNotFoundError. Can/Should I manually add dependencies to a BUILD file? Thanks

Your second codeblock looks like an absolute path, is that correct, or a typo?

a typo 🙂

Can you elaborate more? What dependency are you expecting it to find? Are you importing the module? Any additional info is extremely helpful 🙂

Sure, my use case is to break this poetry project into several packages. Before refactoring it I’ve tried installing Pants as is with this toml:

[GLOBAL]
pants_version = "2.12.0"

backend_packages.add = [
  "pants.backend.python",
  "pants.backend.python.lint.black",
]

[anonymous-telemetry]
enabled = false

[source]
root_patterns = ["/"]

[python]
tailor_ignore_solitary_init_files = false

[python-infer]
inits = true

After ./pants tailor, when running

./pants test tests/test_exporter_factory.py

I get

No module named 'opentelemetry'

even-though the relevant package (opentelemetry-sdk in this case) appears under root when running

./pants dependencies ::

Since the package name

opentelemetry-sdk

and the module name

opentelemetry

don't match, you'll want to set `module_mapping`: https://www.pantsbuild.org/docs/python-third-party-dependencies#use-modules-and-module_mapping-when-the-module-name-is-not-standard

Thanks! Will do

Usability take way, module not found errors could potentially drop a bread crumb about module mappings..

That's an interesting idea. But not sure how we'd do that since the error is coming from the python process we're running 🤔

Ah. I've had ideas in the past about generically looking at error messages and augment them with additional context/details etc. Such as errors from pex or its subprocesses where information may be missing at the source of an error.