nox-poetry crashes with TypeError: slice indices must be integers or None or have an __index__ method

[cjolowicz]

nox-poetry crashes in the GA workflow when parsing requirements with packaging < 21.1 and pyparsing >= 3:

  File ".../python3.9/site-packages/packaging/requirements.py", line 81, in <lambda>
    lambda s, l, t: Marker(s[t._original_start : t._original_end])
TypeError: slice indices must be integers or None or have an __index__ method

The latest version for packaging is not installed because Poetry depends on packaging < 21.0.

There is a workaround for this, adding pyparsing < 3 to .github/workflows/constraints.txt.

A better fix would be to install Poetry and Nox in separate environments, using a tool like pipx.

Traceback

❯ nox -s mypy
nox > Running session mypy-3.9
nox > Creating virtual environment (virtualenv) using python3.9 in .nox/mypy-3-9
nox > poetry build --format=wheel
nox > pip uninstall --yes file:///Users/cjolowicz/Code/github.com/cjolowicz/cutty/dist/cutty-0.15.0-py3-none-any.whl
nox > poetry export --format=requirements.txt --dev --without-hashes
nox > Session mypy-3.9 raised exception TypeError('slice indices must be integers or None or have an __index__ method')
Traceback (most recent call last):
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox/sessions.py", line 626, in execute
    self.func(session)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox/_decorators.py", line 54, in __call__
    return self.func(*args, **kwargs)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 43, in wrapper
    function(proxy, *_args, **_kwargs)
  File "/Users/cjolowicz/Code/github.com/cjolowicz/cutty/noxfile.py", line 128, in mypy
    session.install(".")
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 290, in install
    return self.poetry.install(*args, **kwargs)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 149, in install
    requirements = self.export_requirements()
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 224, in export_requirements
    constraints = to_constraints(self.poetry.export())
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 90, in to_constraints
    return "\n".join(_to_constraints())
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 86, in _to_constraints
    constraint = to_constraint(requirement, line)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/nox_poetry/sessions.py", line 68, in to_constraint
    requirement = Requirement(requirement_string)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/packaging/requirements.py", line 113, in __init__
    req = REQUIREMENT.parseString(requirement_string)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 1100, in parse_string
    loc, tokens = self._parse(instring, 0)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 790, in _parseNoCache
    loc, tokens = self.parseImpl(instring, pre_loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 3810, in parseImpl
    loc, exprtokens = e._parse(instring, loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 790, in _parseNoCache
    loc, tokens = self.parseImpl(instring, pre_loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 4024, in parseImpl
    return e._parse(
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 790, in _parseNoCache
    loc, tokens = self.parseImpl(instring, pre_loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 3810, in parseImpl
    loc, exprtokens = e._parse(instring, loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 790, in _parseNoCache
    loc, tokens = self.parseImpl(instring, pre_loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 4854, in parseImpl
    loc, tokens = self_expr._parse(instring, loc, doActions, callPreParse=False)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 790, in _parseNoCache
    loc, tokens = self.parseImpl(instring, pre_loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 3810, in parseImpl
    loc, exprtokens = e._parse(instring, loc, doActions)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 827, in _parseNoCache
    tokens = fn(instring, tokens_start, ret_tokens)
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/pyparsing/core.py", line 283, in wrapper
    ret = func(*args[limit:])
  File "/Users/cjolowicz/.local/pipx/venvs/nox/lib/python3.9/site-packages/packaging/requirements.py", line 81, in <lambda>
    lambda s, l, t: Marker(s[t._original_start : t._original_end])
TypeError: slice indices must be integers or None or have an __index__ method
nox > Session mypy-3.9 failed.

[cjolowicz]

See pypa/packaging#482 for the upstream discussion.

[layday]

Just FYI the linked PR is unrelated. This is a regression in pyparsing 3.0.5 and cutting a new packaging release without excluding 3.0.5 will break packaging for everyone (!).

[cjolowicz]

Thanks for the heads up @layday

[heiderich]

I can confirm that the issue persists with release 2021.11.8. This does not surprise me, as #1051 only touches the CI).

[cjolowicz]

@heiderich Can you post the output of pip freeze in the environment where you see this error?

The latest release of packaging (21.2) depends on pyparsing < 3, so you should only see this if you have an older version of packaging. #1051 isolated the environments of Poetry and nox-poetry because Poetry forced the older version of packaging, triggering the crash in nox-poetry.

[heiderich]

It turned out that I did not follow the installation instructions closely and did not install the requirements (nox, poetry) in separate environments. Indeed I had an older version of packaging (20.9). Sorry for the noise!

[cjolowicz]

Thanks for reporting back @heiderich