Why doesn't hatch find an installed python interpreter to be used in a test environment ?

[manuel-koch]

I have a python project inside a sub-directory of my git-repo.
The pyproject.toml contains this snippet to configure python interpreter for the test environment(s):

[[tool.hatch.envs.test.matrix]]
python = [
  "310"
]

This python version seems to be installed:

$ hatch --version
Hatch, version 1.14.0

$ hatch python show
    Installed     
┏━━━━━━┳━━━━━━━━━┓
┃ Name ┃ Version ┃
┡━━━━━━╇━━━━━━━━━┩
│ 3.10 │ 3.10.16 │
├──────┼─────────┤
│ 3.12 │ 3.12.8  │
└──────┴─────────┘

But when I try to run tests, hatch can't setup that env !?

$ make test
cd src \
        && hatch run test:cov
Skipped 1 incompatible environment:
test.py310 -> cannot locate Python: 310

I have tried using 3.10 as the version string too, but that isn't found either.
It works though when using 312 as the version string.

[tayfuryldz]

hatch python show and environment interpreter resolution are related, but they are not the same lookup path in older Hatch releases. The important clue here is that 3.12 works while the Hatch-managed 3.10 shown by hatch python show does not.

Current Hatch makes the resolution policy explicit: virtual environments can resolve from two sources, external (interpreters already on PATH) and internal (Hatch-managed distributions), with both enabled by default:

[tool.hatch.envs.test]
python-sources = ["external", "internal"]

So on a current Hatch release, an interpreter installed by:

hatch python install 3.10
hatch python find 3.10

is a valid internal source for an environment selecting Python 3.10.

Given that the report is from Hatch 1.14.0, I would first upgrade Hatch and recreate the failed test environment rather than changing 310 to 3.10 repeatedly:

hatch self update
hatch python find 3.10
hatch env remove test.py310
hatch run test.py310:cov

If you intentionally want to force only the managed interpreter, current Hatch also lets you make that explicit:

[tool.hatch.envs.test]
python-sources = ["internal"]

Conversely, python-sources = ["external"] means “only search PATH”, so a Python that merely appears in hatch python show would not satisfy it.

The subdirectory layout of the project should not itself prevent discovery of an internally managed Python. The useful diagnostic is hatch python find 3.10: it tells you whether Hatch can resolve the managed distribution to an executable, whereas hatch python show only establishes that Hatch has an installed distribution record.