Hello I'm testing pants with my repo containing some Python code and I have troubles to figure out what to put as source roots and where to place BUILD files. ./pants tailor doesn't find anything. My projects have a dir structure with a src and tests directory and I didn't find any examples on the doc with that. It looks like that:

├── pants
├── pants.toml
└── py
    ├── libraries
    │   └── libtutu
    │       ├── LICENSE
    │       ├── pyproject.toml
    │       ├── README.md
    │       ├── setup.cfg
    │       └── src
    │           └── libtutu
    │               └── __init__.py
    └── projects
        ├── tata
        │   ├── LICENSE
        │   ├── pyproject.toml
        │   ├── README.md
        │   ├── setup.cfg
        │   └── src
        │       ├── tata
        │           └── __init__.py
        └── standalone
            ├── LICENSE
            ├── pyproject.toml
            ├── README.md
            ├── setup.cfg
            ├── src
            │   ├── standalone
            │       └── __init__.py
            └── tests
                └── test_dummy.py

Does anyone have an example I could follow for when you have the src/ and tests/ directory?

For Python, source roots == PYTHONPATH. So the answer is whatever the PYTHONPATH would need to be (without installing any projects) to

import tata

(for example). So, it looks like your source roots are

["py/libraries/libtutu/src", "py/projects/tata/src", "py/projects/standalone/src"]

.

Hum, if I set marker_filenames then the source root is one level before src, is that a problem? Then I'm not sure where to place the BUILD files and what to place inside. For example, if I just place

python_tests(
    name="tests"
)

on py/projects/standalone/tests/BUILD pants can find the tests but can't import what is in src.

Ah, yeah. I'm sorry, bad advice. Marker filenames won't work; so just list them out like in my 1st example. After you have the source roots configured, try

./pants tailor

again and just go with the BUILD files it generates unless you have some strong objections or things still aren't working.

tailor just put a BUILD in standalone/tests but nothing else 😕

Can you share your complete

pants.toml

?

[GLOBAL]
pants_version = "2.12.0+git5d31cdb5"
backend_packages = [
    "pants.backend.python",
    "pants.backend.python.lint.black",
    "pants.backend.python.lint.flake8",
    "pants.backend.python.typecheck.mypy"
]

[anonymous-telemetry]
enabled = false

[source]
#marker_filenames = ["pyproject.toml"]
#root_patterns = ["/"]

[python]
interpreter_constraints = ["CPython==3.10.*"]

On the shell I get

%./pants roots
.
py/libraries/libtutu/src
py/projects/standalone/src
py/projects/tata/src

%./pants tailor
Created py/projects/standalone/tests/BUILD:
  - Add python_tests target tests

Ok, thanks. I'm poking around a bit here using that.

ah ok 🙂 The results are pretty simple

python_sources()

is it ok or do you see particular options I should set in general?

It looks Ok. The simple BUILD files are a reflection of where we're headed, which is no BUILD files unless you need to actually tell Pants something particular about your code. These ~empty BUILD files are just a reflection of the past.

Ok. If I need a 3rd party library, should I declare it manually in BUILD? Like with

python_requirement

?

It's up to you. Some folks use a Pip-style

requirements.txt

and a BUILD file next to it with

python_requirements()

, which is a macro that reads in all the

requirements.txt

requirements and creates a `python_requirement`for each for you. Likewise

poetry_requirements()

in a BUILD file next to

pyproject.toml

for Poetry-based projects, If you don't already use a requirements.txt though manually declaring in a BUILD file is fine.

Well, I use either a pyproject.toml but more the PEP621 version than poetry, I don't know if there is a difference. Otherwise, I use setup.cfg + setuptools. I have a requirements.txt but this is usually for the dev dependencies like pytest or coverage.

Yeah, we should definitely add support for PEP-621

dependencies

and probably

requires-python

too (for setting various

interpreter_constraints

options). You're welcome.

cool, thanks!