What alternative environments are thoughtable to support projects with python 2.7 downward compatibility?

[return42]

Since virtualenv has dropped support for running under Python 2 in v20.16.0 (2022-07-25) we can no longer build py2.7 environments.

Option values python=["py27", "/usr/bin/python2.7", "pypy2.7"] do no longer work / compare: #1360

Below you see my setup to run tests in a python 2.7 environment by::

$ hatch -v run py27:test

This solution has a various quirks & drawbacks:

• the requirements of the project are hard coded / 'python-dateutil >=2.4.0' 'six >=1.16.0'
• requires installed python2.7 runtime with virtualenv installed
• creates .venv27 folder in the project root folder

May someone of you can suggest better alternatives?

---

[tool.hatch.envs.py27]
detached = true

[tool.hatch.envs.py27.scripts]

# to run py27.scripts a python2 and a virtualenv installation is needed::
#
#   $ sudo apt install python2
#   $ curl https://bootstrap.pypa.io/pip/2.7/get-pip.py --output get-pip.py
#   $ python2 get-pip.py
#   $ pip2 --version
#   pip 20.3.4 from ~/.local/lib/python2.7/site-packages/pip (python 2.7)
#   $ python2 -m pip install virtualenv
#   $ python2 -m virtualenv --version
#   virtualenv 20.15.1 from ~/.local/lib/python2.7/site-packages/virtualenv/__init__.pyc

venv27 = """
python2 -m virtualenv .venv27
.venv27/bin/python -m pip install --upgrade pip 'python-dateutil >=2.4.0' 'six >=1.16.0' 'pylint ==1.9.5'
.venv27/bin/python -m pip install -e .
"""

clean = "rm -rf .venv27"

pylint = """
.venv27/bin/python -m pylint \
  --output-format=parseable \
  --disable=bad-option-value,bad-continuation,superfluous-parens,old-style-class \
  ./src
"""

test = [
   "venv27",
   "pylint",
   "clean",
]

[ofek]

Can you create the environment yourself and then point to the path? https://hatch.pypa.io/latest/plugins/environment/virtual/#location

[return42]

I could, TBH this is what I do currently .. with a Makefile .. but we switch to hatch to get rid of the Makefile .. not all developers have make installed (e.g. MS-Wndows users) and not all developers in the python eco-system know how to write Makefiles .. with hatch we can do everything we need in the python 3 world, but we have this py2.7 backward compatibility we want to support for a while and therefore we need a solution .. TBH the tool.hatch.envs.py27 environment is just a snippet of a more complex pyproject.toml and exists only to run some commands.

In sense of "single point of definition": we have dependencies defined in the [project] section:

[project]
requires-python = ">=2.7"
dependencies = [
    "python-dateutil >=2.4.0",
    "six >=1.16.0",
]

is there a chance to reference this dependencies in the py27.scripts .. instead of doubling it like I now do?

[tool.hatch.envs.py27.scripts]
venv27 = """
python2 -m virtualenv .venv27
.venv27/bin/python -m pip install 'python-dateutil >=2.4.0' 'six >=1.16.0' ..

Something like pip install ${project.dependencies} .. AFAIK in toml this is not possible but may be in the script definitions of hutch?

Or a python/template (jinja?) expression like {{ ' '.join(project.dependencies) }}