Fix wheel tag determination

src/poetry/core/masonry/builders/wheel.py

@@ -8,6 +8,7 @@
 import shutil
 import stat
 import subprocess
+import sys
 import tempfile
 import zipfile
 
@@ -17,7 +18,7 @@
 from typing import TYPE_CHECKING
 from typing import TextIO
 
-from packaging.tags import sys_tags
+import packaging.tags
 
 from poetry.core import __version__
 from poetry.core.constraints.version import parse_constraint
@@ -26,6 +27,7 @@
 from poetry.core.masonry.utils.helpers import distribution_name
 from poetry.core.masonry.utils.helpers import normalize_file_permissions
 from poetry.core.masonry.utils.package_include import PackageInclude
+from poetry.core.utils.helpers import decode
 from poetry.core.utils.helpers import temporary_directory
 
 
@@ -327,16 +329,59 @@ def dist_info_name(self, name: NormalizedName, version: str) -> str:
         escaped_name = distribution_name(name)
         return f"{escaped_name}-{version}.dist-info"
 
+    def _get_sys_tags(self) -> list[str]:
+        """Get sys_tags via subprocess.
+        Required if poetry-core is not run inside the build environment.
+        """
+        try:
+            output = subprocess.check_output(
+                [
+                    self.executable.as_posix(),
+                    "-c",
+                    f"""
+import importlib.util
+import sys
+
+from pathlib import Path
+
+spec = importlib.util.spec_from_file_location(
+    "packaging", Path(r"{packaging.__file__}")
+)
+
+packaging = importlib.util.module_from_spec(spec)
+sys.modules[spec.name] = packaging
+
+spec = importlib.util.spec_from_file_location(
+    "packaging.tags", Path(r"{packaging.tags.__file__}")
+)
+packaging_tags = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(packaging_tags)
+for t in packaging_tags.sys_tags():
+    print(t.interpreter, t.abi, t.platform, sep="-")
+""",
+                ],
+                stderr=subprocess.STDOUT,
+            )
+        except subprocess.CalledProcessError as e:
+            raise RuntimeError(
+                "Failed to get sys_tags for python interpreter"
+                f" '{self.executable.as_posix()}':\n{decode(e.output)}"
+            )
+        return decode(output).strip().splitlines()
+
     @property
     def tag(self) -> str:
         if self._package.build_script:
-            sys_tag = next(sys_tags())
+            if self.executable != Path(sys.executable):
+                # poetry-core is not run in the build environment
+                # -> this is probably not a PEP 517 build but a poetry build
+                return self._get_sys_tags()[0]
+            sys_tag = next(packaging.tags.sys_tags())
             tag = (sys_tag.interpreter, sys_tag.abi, sys_tag.platform)
         else:
             platform = "any"
             impl = "py2.py3" if self.supports_python2() else "py3"
             tag = (impl, "none", platform)
-
         return "-".join(tag)
 
     def _add_file(

src/poetry/core/utils/helpers.py

@@ -10,6 +10,7 @@
 import warnings
 
 from contextlib import contextmanager
+from contextlib import suppress
 from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import Any
@@ -27,6 +28,19 @@ def combine_unicode(string: str) -> str:
     return unicodedata.normalize("NFC", string)
 
 
+def decode(string: bytes | str, encodings: list[str] | None = None) -> str:
+    if not isinstance(string, bytes):
+        return string
+
+    encodings = encodings or ["utf-8", "latin1", "ascii"]
+
+    for encoding in encodings:
+        with suppress(UnicodeEncodeError, UnicodeDecodeError):
+            return string.decode(encoding)
+
+    return string.decode(encodings[0], errors="ignore")
+
+
 def module_name(name: str) -> str:
     return canonicalize_name(name).replace("-", "_")
 

tests/masonry/builders/test_wheel.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import os
+import re
 import shutil
 import zipfile
 
@@ -350,3 +351,22 @@ def capturing_fdopen(*args: Any, **kwargs: Any) -> TextIO | None:
 
     assert fd_file[0] is not None
     assert fd_file[0].closed
+
+
+@pytest.mark.parametrize("in_venv_build", [True, False])
+def test_tag(in_venv_build: bool, mocker: MockerFixture) -> None:
+    """Tests that tag returns a valid tag if a build script is used,
+    no matter if poetry-core lives inside the build environment or not.
+    """
+    root = fixtures_dir / "extended"
+    builder = WheelBuilder(Factory().create_poetry(root))
+
+    get_sys_tags_spy = mocker.spy(builder, "_get_sys_tags")
+    if not in_venv_build:
+        mocker.patch("sys.executable", "other/python")
+
+    assert re.match("^cp[23]_?\\d+-cp[23]_?\\d+m?u?-.+$", builder.tag)
+    if in_venv_build:
+        get_sys_tags_spy.assert_not_called()
+    else:
+        get_sys_tags_spy.assert_called()