I have a question about Python interpreter constraints. I'm moving us from 3.7 to 3.8. In

pants.toml

, I have:

[python]
interpreter_constraints = [">=3.8,<4"]

[python-bootstrap]
search_path = ["<PYENV_LOCAL>", "<PYENV>", "<PATH>"]

My

.python-version

file has

3.8.13

. My

black

configuration is:

[black]
lockfile = "3rdparty/python/black.lockfile"
version = "black>=22.3.0"
config = "pyproject.toml"

and

black.lockfile

contains the following metadata:

// --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
// {
//   "version": 2,
//   "valid_for_interpreter_constraints": [
//     "CPython<4,>=3.8"
//   ],
//   "generated_with_requirements": [
//     "black>=22.3.0",
//     "typing-extensions>=3.10.0.0; python_version < \"3.10\""
//   ]
// }
// --- END PANTS LOCKFILE METADATA ---

When I run

./pants fmt ::

,

black

runs fine. However, when I run

./pants update-build-files

, I get the following error:

11:33:26.58 [ERROR] 1 Exception encountered:

  InvalidLockfileError: You are using the lockfile at 3rdparty/python/black.lockfile to install the tool `black`, but it is not compatible with your configuration: 

- You have set interpreter constraints (`CPython<4,>=3.7`) that are not compatible with those used to generate the lockfile (`CPython<4,>=3.8`). You can fix this by not setting `[black].interpreter_constraints`, or by using a new custom lockfile. 

To regenerate your lockfile based on your current configuration, run `./pants generate-lockfiles --resolve=black`.

Why would

black

work in one instance but not the other, and where might that

>=3.7

constraint be coming from? Thanks in advance!

This is https://github.com/pantsbuild/pants/issues/14912, which indeed is very confusing. I don't know how to fix it but it keeps tripping people up

Whoa, spooky. The workaround seems to work, though, so thanks for the pointer 👍

K Stu's suggestion will work I think. Gonna see if I can knock this out today 🤞