Why is this package forbidden?

[BeyondEvil]

$ python --version
Python 3.9.10

$ poetry add pytest-metadata
Using version ^2.0.1 for pytest-metadata

Updating dependencies
Resolving dependencies... (0.0s)

  SolverProblemError

  The current project's Python requirement (>=3.9,<4.0) is not compatible with some of the required packages Python requirement:
    - pytest-metadata requires Python >=3.7.0,<3.11.0, so it will not be satisfied for Python >=3.11.0,<4.0

  Because no versions of pytest-metadata match >2.0.1,<3.0.0
   and pytest-metadata (2.0.1) requires Python >=3.7.0,<3.11.0, pytest-metadata is forbidden.
  So, because testing depends on pytest-metadata (^2.0.1), version solving failed.

Package toml

Project toml:

[tool.poetry]
name = "testing"
version = "0.1.0"
description = ""
authors = ["Jim Brännlund <jim.brannlund@gmail.com>"]

[tool.poetry.dependencies]
python = "^3.9"

[tool.poetry.dev-dependencies]

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

Project python is 3.9.10 which is within the package requirement of >=3.7.0,<3.11.0, so why is it "forbidden"?

[clintonroy]

Project python is 3.9.10 which is within the package requirement of >=3.7.0,<3.11.0, so why is it "forbidden"?

The project python is not 3.9.10 it is "^3.9", which expands to 3.9,3.10,3.11,3.12...3.99 up until but not including 4.0.

Try restricting the project python to just 3.9.* for example, that will be a subset of what pytest-metadata works with.

[BeyondEvil]

That makes zero sense to me.

That means that the dependency then dictates what constraints I need to put in the project.

My expectation would be that Poetry checks the current version that the project is using (3.9.10) which is within the requirements and allows it.

Now, if the current version was 3.11.0 or higher (with the pyproject.toml still having ^3.9), then I would expect Poetry to reject it.

[clintonroy]

That means that the dependency then dictates what constraints I need to put in the project.

Correct. All the dependencies you choose dictate your project's deps. As an example, if one of your dependencies requires an arm processor, your project requires an arm processor, and there's just nothing you can do about that.

My expectation would be that Poetry checks the current version that the project is using (3.9.10) which is within the requirements and allows it.

The range of python versions your project requires is specified in the pyproject.toml python field. This is separate from all the versions of python you have installed locally.

Now, if the current version was 3.11.0 or higher (with the pyproject.toml still having ^3.9), then I would expect Poetry to reject it.

I think the problem here is poetry defaulting to it's caret style of dependencies, that is far too wide a range for my liking. If you change the project's python range to "~3.9.10" I have a feeling that will come closer to your expectations.

[BeyondEvil]

That means that the dependency then dictates what constraints I need to put in the project.

Correct. All the dependencies you choose dictate your project's deps. As an example, if one of your dependencies requires an arm processor, your project requires an arm processor, and there's just nothing you can do about that.

I think that's an apples and oranges thing, but I'm too tired to articulate why.

My expectation would be that Poetry checks the current version that the project is using (3.9.10) which is within the requirements and allows it.

The range of python versions your project requires is specified in the pyproject.toml python field. This is separate from all the versions of python you have installed locally.

While that might be true, it's also the actual version currently being used by the project. Now if I were to upgrade the project to a python version which doesn't jive with a dependency - then I would expect it to complain.

Now, if the current version was 3.11.0 or higher (with the pyproject.toml still having ^3.9), then I would expect Poetry to reject it.

I think the problem here is poetry defaulting to it's caret style of dependencies, that is far too wide a range for my liking. If you change the project's python range to "~3.9.10" I have a feeling that will come closer to your expectations.

Agreed. And yes, changing to tilde makes it work.

[igor-petrik-invitae]

That means that the dependency then dictates what constraints I need to put in the project.

Correct. All the dependencies you choose dictate your project's deps. As an example, if one of your dependencies requires an arm processor, your project requires an arm processor, and there's just nothing you can do about that.

I think that's an apples and oranges thing, but I'm too tired to articulate why.

I think about it this way:

1. I state in my pyproject.toml that my project is guaranteed to run on python = ^3.9 (i.e. >=3.9, <4.0)
2. My project requires a package
   1. All currently available versions of that package only guarantee that they support python >3.7, <3.11
3. Therefore - there is no way that my package can guarantee support for python >= 3.11, because something it depends on to function cannot guarantee that support; therefore, if my project truly requires that package, I'm SOL for guaranteeing that my project will run on 3.11.

[BeyondEvil]

I see now @igor-petrik-invitae

Thanks for explanation. 🙇