fix support of free-threaded Python if Poetry itself is not installed with a free-threaded Python

[radoering]

Pull Request Check List

Resolves: https://github.com/orgs/python-poetry/discussions/10601

• Added tests for changed code.
• Updated documentation for changed code.

Summary by Sourcery

Add support for free-threaded Python interpreters by introducing a free_threading marker and updating tag generation to include or exclude the 't' ABI suffix accordingly.

Bug Fixes:

• Ensure get_supported_tags omits the 't' ABI when free_threading is false and includes it when true

Enhancements:

• Add free_threading field to MarkerEnv and populate it in system_env and script_strings

Tests:

• Add test_env_get_supported_tags_free_threading to verify tag lists for both free-threaded and standard interpreters

[sourcery-ai]

Reviewer's Guide

Add detection and propagation of free-threaded (GIL-disabled) Python build in the environment markers and tag generation logic, and include tests to verify ABI ‘t’ suffix handling when free-threading is enabled.

Class diagram for updated MarkerEnv and tag generation

classDiagram
    class MarkerEnv {
        str interpreter_name
        str interpreter_version
        str sysconfig_platform
        bool free_threading
    }
    class Env {
        <<abstract>>
    }
    class VirtualEnv {
        get_supported_tags() : list[Tag]
    }
    MarkerEnv <|-- Env
    Env <|-- VirtualEnv
    VirtualEnv --> MarkerEnv : uses

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Flow diagram for propagation of free_threading marker

flowchart TD
    A["sysconfig.get_config_var('Py_GIL_DISABLED')"] --> B["Set free_threading in MarkerEnv"]
    B --> C["get_supported_tags() uses free_threading"]
    C --> D["ABI 't' suffix added if free_threading is True"]

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File-Level Changes

Change	Details	Files
Extend the MarkerEnv to include a free_threading flag and populate it during environment introspection	Add free_threading field to MarkerEnv type Set free_threading from sysconfig.get_config_var("Py_GIL_DISABLED") in both script_strings and system_env	src/poetry/utils/env/base_env.py src/poetry/utils/env/script_strings.py src/poetry/utils/env/system_env.py
Make VirtualEnv.get_supported_tags aware of free-threaded builds by supplying custom ABI list	Read free_threading from marker_env When CPython and free_threading is true, set abis to ["t"] Pass abis into cpython_tags instead of relying on default ABIs	src/poetry/utils/env/virtual_env.py
Add pytest to verify supported tags include or exclude 't' ABI based on free_threading	Introduce test_env_get_supported_tags_free_threading with skip for non-CPython Check absence of 't' suffix when free_threading is false, and presence when toggled to true	tests/utils/env/test_env.py

Possibly linked issues

• How to take into account ABI tag of a wheel : cp314-cp314t for an python 3.14t venv ? #10601: The PR adds logic to correctly determine and handle the 'free_threading' status, resolving the AttributeError when virtualenv expects this attribute.

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[sourcery-ai]

Hey there - I've reviewed your changes - here's some feedback:

• Explicitly convert sysconfig.get_config_var("Py_GIL_DISABLED") to a boolean (e.g. bool(...) or compare to 1) to avoid storing non‐boolean values like '1' in marker_env.
• Consider centralizing the free_threading detection logic instead of duplicating it in both script_strings.py and system_env.py to keep them in sync.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Explicitly convert sysconfig.get_config_var("Py_GIL_DISABLED") to a boolean (e.g. bool(...) or compare to 1) to avoid storing non‐boolean values like '1' in marker_env.
- Consider centralizing the free_threading detection logic instead of duplicating it in both script_strings.py and system_env.py to keep them in sync.

## Individual Comments

### Comment 1
<location> `src/poetry/utils/env/script_strings.py:89` </location>
<code_context>
     ),
     "interpreter_version": interpreter_version(),
     "sysconfig_platform": sysconfig.get_platform(),
+    "free_threading": sysconfig.get_config_var("Py_GIL_DISABLED") or False,
 }

</code_context>

<issue_to_address>
**suggestion:** Explicitly cast Py_GIL_DISABLED to bool for clarity.

Casting to bool ensures consistent boolean output, regardless of the original type returned by sysconfig.get_config_var.

```suggestion
    "free_threading": bool(sysconfig.get_config_var("Py_GIL_DISABLED")),
```
</issue_to_address>

### Comment 2
<location> `src/poetry/utils/env/system_env.py:77` </location>
<code_context>
     ),
     "interpreter_version": interpreter_version(),
     "sysconfig_platform": sysconfig.get_platform(),
+    "free_threading": sysconfig.get_config_var("Py_GIL_DISABLED") or False,
 }

</code_context>

<issue_to_address>
**suggestion:** Explicitly cast Py_GIL_DISABLED to bool for consistency.

Casting to bool prevents unexpected behavior if Py_GIL_DISABLED is not strictly boolean.

```suggestion
            "free_threading": bool(sysconfig.get_config_var("Py_GIL_DISABLED")),
```
</issue_to_address>

### Comment 3
<location> `src/poetry/utils/env/virtual_env.py:61` </location>
<code_context>
    def get_supported_tags(self) -> list[Tag]:
        from packaging.tags import compatible_tags
        from packaging.tags import cpython_tags
        from packaging.tags import generic_tags

        python = self.version_info[:3]
        interpreter_name = self.marker_env["interpreter_name"]
        interpreter_version = self.marker_env["interpreter_version"]
        sysconfig_platform = self.marker_env["sysconfig_platform"]
        free_threading = self.marker_env["free_threading"]

        abis: list[str] | None = None
        if interpreter_name == "pp":
            interpreter = "pp3"
        elif interpreter_name == "cp":
            interpreter = f"{interpreter_name}{interpreter_version}"
            if free_threading:
                abis = [f"{interpreter}t"]
        else:
            interpreter = None

        # Why using sysconfig.get_platform() and not ...
        # ... platform.machine()
        #  This one is also different for x86_64 Linux and aarch64 Linux,
        #  but it is the same for a 32 Bit and a 64 Bit Python on Windows!
        # ... platform.architecture()
        #  This one is also different for a 32 Bit and a 64 Bit Python on Windows,
        #  but it is the same for x86_64 Linux and aarch64 Linux!
        platforms = None
        if sysconfig_platform != sysconfig.get_platform():
            # Relevant for the following use cases, for example:
            # - using a 32 Bit Python on a 64 Bit Windows
            # - using an emulated aarch Python on an x86_64 Linux
            output = self.run_python_script(GET_PLATFORMS)
            platforms = json.loads(output)

        return [
            *(
                cpython_tags(python, abis=abis, platforms=platforms)
                if interpreter_name == "cp"
                else generic_tags(platforms=platforms)
            ),
            *compatible_tags(python, interpreter=interpreter, platforms=platforms),
        ]

</code_context>

<issue_to_address>
**issue (code-quality):** We've found these issues:

- Move assignments closer to their usage ([`move-assign`](https://docs.sourcery.ai/Reference/Default-Rules/refactorings/move-assign/))
- Simplify conditional into switch-like form [×2] ([`switch`](https://docs.sourcery.ai/Reference/Default-Rules/refactorings/switch/))
</issue_to_address>

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