Strange skipping of dependencies when python requirement is specified ("Not needed for the current environment")

[adithyabsk]

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

Poetry Debug Info

Poetry
Version: 1.0.5
Python:  3.6.8

Virtualenv
Python:         3.6.8
Implementation: CPython
Path:           /Users/adithyabalaji/.pyenv/versions/3.6.8/envs/test368
Valid:          True

System
Platform: darwin
OS:       posix
Python:   /Users/adithyabalaji/.pyenv/versions/3.6.8

MVP Erroring pyproject.toml

[tool.poetry]
name = "test"
version = "0.1.0"
description = ""
authors = ["Adithya"]

[tool.poetry.dependencies]
python = "^3.6.1"

[tool.poetry.dev-dependencies]
seed-isort-config = { version = "^2.1.0", python = "^3.6.1"}

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"

Issue

When I run poetry install I expect all packages to be installed when running python 3.6.8, that doesn't seem to happen and I get the following output. It does work if I remove the python requirement on the dependency.

While this configuration doesn't make much sense in this case, consider the case where multiple python versions need to be supported (ie in my case I'm making the last release for python 2.7 for a package and thus, need to support multiple python versions at least for one more release.

I also know that this bug isn't isolated to seed-isort-config, I tried a few other packages just to be safe and found it produces the same result for flake8, etc... So it seems to be a poetry issue.

$ poetry install -vvv
Using virtualenv: /Users/adithyabalaji/.pyenv/versions/3.6.8/envs/test368
Installing dependencies from lock file

No dependencies to install or update

  - Skipping cached-property (1.5.1) Not needed for the current environment
  - Skipping aspy.refactor-imports (2.1.0) Not needed for the current environment
  - Skipping seed-isort-config (2.1.0) Not needed for the current environment

[adithyabsk]

Might be related to #2177

Although the issues are unrelated, I tried the suggested resolution and it didn't work in my case as well. #2177 (comment)

[adithyabsk]

I just went through and tested all prior poetry versions down to 0.12.13 which is where I gave up and the bug seems to exist in each of those releases.

[adithyabsk]

Okay, I think I've figured out the bug after some debugging. Basically, dependency resolution that includes a python patch version breaks down in a weird way due to the difference between the python_version and python_full_version

[adithyabsk]

The short-term solution to my problem is to not use patch versions.

Looking at the codebase it seems that it will be somewhat difficult to refactor the codebase to allow for patch version python version constraints. The concept of python_version is hardcoded in a lot of places and manifests itself in the lock file as well. Someone with a better understanding of the project will have to chime in to note whether fixing this is even feasible.

An example of why this might be difficult to re-factor is here. It's where I left off and if someone decides to take this up, what needs to be done, as far as I understand it, is to modify the create_nested_marker function to determine what the "name" of the constraint is if it is not passed in so it can determine whether to use python_version or python_full_version. I'd also note that there seem to be two versions of the function in the codebase:

create_nested_marker in utils and the private _created_nested_marker in the Dependency class.

poetry/poetry/packages/package.py

Line 349 in d27a119

if not markers:

            if not markers:
                marker = AnyMarker()
                if python_versions:
                    dependency.python_versions = python_versions
                    marker = marker.intersect(
                        parse_marker(
                            create_nested_marker(
                                "python_version", dependency.python_constraint
                            )
                        )
                    )

[dimbleby]

This was duplicated by #3347, and is now long since fixed.

[github-actions]

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