Support for external packages and builders (#2235)

1 files changed, 55 insertions, 2 deletions

diff --git a/src/tox/tox_env/python/package.py b/src/tox/tox_env/python/package.py
index 5964bcaf..2d43a96f 100644
--- a/src/tox/tox_env/python/package.py
+++ b/src/tox/tox_env/python/package.py
@@ -3,12 +3,19 @@ A tox build environment that handles Python packages.
 """
 from abc import ABC, abstractmethod
 from pathlib import Path
-from typing import Any, Sequence, Tuple
+from typing import TYPE_CHECKING, Any, Dict, Generator, Iterator, Optional, Sequence, Tuple, Union, cast
 
 from packaging.requirements import Requirement
 
+from ...config.sets import EnvConfigSet
+from ..api import ToxEnvCreateArgs
 from ..package import Package, PackageToxEnv, PathPackage
+from ..runner import RunToxEnv
 from .api import Python
+from .pip.req_file import PythonDeps
+
+if TYPE_CHECKING:
+    from tox.config.main import Config
 
 
 class PythonPackage(Package):
@@ -34,6 +41,10 @@ class DevLegacyPackage(PythonPathPackageWithDeps):
 
 
 class PythonPackageToxEnv(Python, PackageToxEnv, ABC):
+    def __init__(self, create_args: ToxEnvCreateArgs) -> None:
+        self._wheel_build_envs: Dict[str, PythonPackageToxEnv] = {}
+        super().__init__(create_args)
+
     def register_config(self) -> None:
         super().register_config()
 
@@ -43,5 +54,47 @@ class PythonPackageToxEnv(Python, PackageToxEnv, ABC):
         self.installer.install(self.requires(), PythonPackageToxEnv.__name__, "requires")
 
     @abstractmethod
-    def requires(self) -> Tuple[Requirement, ...]:
+    def requires(self) -> Union[Tuple[Requirement, ...], PythonDeps]:
         raise NotImplementedError
+
+    def register_run_env(self, run_env: RunToxEnv) -> Generator[Tuple[str, str], PackageToxEnv, None]:
+        yield from super().register_run_env(run_env)
+        if not isinstance(run_env, Python) or run_env.conf["package"] != "wheel" or "wheel_build_env" in run_env.conf:
+            return
+
+        def default_wheel_tag(conf: "Config", env_name: Optional[str]) -> str:
+            # https://www.python.org/dev/peps/pep-0427/#file-name-convention
+            # when building wheels we need to ensure that the built package is compatible with the target env
+            # compatibility is documented within https://www.python.org/dev/peps/pep-0427/#file-name-convention
+            # a wheel tag example: {distribution}-{version}(-{build tag})?-{python tag}-{abi tag}-{platform tag}.whl
+            # python only code are often compatible at major level (unless universal wheel in which case both 2/3)
+            # c-extension codes are trickier, but as of today both poetry/setuptools uses pypa/wheels logic
+            # https://github.com/pypa/wheel/blob/master/src/wheel/bdist_wheel.py#L234-L280
+            run_py = cast(Python, run_env).base_python
+            if run_py is None:
+                raise ValueError(f"could not resolve base python for {self.conf.name}")
+
+            default_pkg_py = self.base_python
+            if (
+                default_pkg_py.version_no_dot == run_py.version_no_dot
+                and default_pkg_py.impl_lower == run_py.impl_lower
+            ):
+                return self.conf.name
+
+            return f"{self.conf.name}-{run_py.impl_lower}{run_py.version_no_dot}"
+
+        run_env.conf.add_config(
+            keys=["wheel_build_env"],
+            of_type=str,
+            default=default_wheel_tag,
+            desc="wheel tag to use for building applications",
+        )
+        pkg_env = run_env.conf["wheel_build_env"]
+        result = yield pkg_env, run_env.conf["package_tox_env_type"]
+        self._wheel_build_envs[pkg_env] = cast(PythonPackageToxEnv, result)
+
+    def child_pkg_envs(self, run_conf: EnvConfigSet) -> Iterator[PackageToxEnv]:
+        if run_conf["package"] == "wheel":
+            env = self._wheel_build_envs.get(run_conf["wheel_build_env"])
+            if env is not None and env.name != self.name:
+                yield env