Include WHEEL metadata when using PDM and poetry backends (#2881)

Fix https://github.com/tox-dev/tox/issues/2880
Fix https://github.com/tox-dev/tox/issues/2870

4 files changed, 37 insertions, 11 deletions

diff --git a/docs/changelog/2880.bugfix.rst b/docs/changelog/2880.bugfix.rst
new file mode 100644
index 00000000..2ab4c11c
--- /dev/null
+++ b/docs/changelog/2880.bugfix.rst
@@ -0,0 +1,10 @@
+When building a ``wheel`` or ``editable`` package with a PEP 517 backend, no
+longer pass an empty ``metadata_directory`` to the backend ``build_wheel`` or
+``build_editable`` endpoint.
+
+Some backends, such as PDM and poetry, will not generate package metadata in
+the presence of a ``metadata_directory``, even if it is empty.
+
+Prior to this change, attempting to install a wheel created by tox using PDM or
+poetry would return an error like "There is no item named
+'my-package.0.1.dist-info/WHEEL' in the archive" - by :user:`masenf`.
diff --git a/pyproject.toml b/pyproject.toml
index c0b45419..0117ffbc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,7 +29,7 @@ dependencies = [
   "packaging>=23",
   "platformdirs>=2.6.2",
   "pluggy>=1",
-  "pyproject-api>=1.4",
+  "pyproject-api>=1.5",
   'tomli>=2.0.1; python_version < "3.11"',
   "virtualenv>=20.17.1",
   "filelock>=3.9",
diff --git a/src/tox/tox_env/python/virtual_env/package/pyproject.py b/src/tox/tox_env/python/virtual_env/package/pyproject.py
index 1cb31c6f..77508732 100644
--- a/src/tox/tox_env/python/virtual_env/package/pyproject.py
+++ b/src/tox/tox_env/python/virtual_env/package/pyproject.py
@@ -137,6 +137,14 @@ class Pep517VirtualEnvPackager(PythonPackageToxEnv, VirtualEnv):
         meta_folder.mkdir(exist_ok=True)
         return meta_folder
 
+    @property
+    def meta_folder_if_populated(self) -> Path | None:
+        """Return the metadata directory if it contains any files, otherwise None."""
+        meta_folder = self.meta_folder
+        if meta_folder.exists() and tuple(meta_folder.iterdir()):
+            return meta_folder
+        return None
+
     def register_run_env(self, run_env: RunToxEnv) -> Generator[tuple[str, str], PackageToxEnv, None]:
         yield from super().register_run_env(run_env)
         build_type = run_env.conf["package"]
@@ -210,7 +218,7 @@ class Pep517VirtualEnvPackager(PythonPackageToxEnv, VirtualEnv):
                 with self._pkg_lock:
                     wheel = getattr(self._frontend, method)(
                         wheel_directory=self.pkg_dir,
-                        metadata_directory=self.meta_folder,
+                        metadata_directory=self.meta_folder_if_populated,
                         config_settings=self._wheel_config_settings,
                     ).wheel
                     wheel = create_session_view(wheel, self._package_temp_path)
diff --git a/tests/demo_pkg_inline/build.py b/tests/demo_pkg_inline/build.py
index 47df3a3d..22e5dda0 100644
--- a/tests/demo_pkg_inline/build.py
+++ b/tests/demo_pkg_inline/build.py
@@ -21,8 +21,7 @@ wheel = "{}/WHEEL".format(dist_info)
 record = "{}/RECORD".format(dist_info)
 content = {
     logic: "def do():\n    print('greetings from {}')".format(name),
-    plugin: dedent(
-        """
+    plugin: """
         try:
             from tox.plugin import impl
             from tox.tox_env.python.virtual_env.runner import VirtualEnvRunner
@@ -37,14 +36,13 @@ content = {
             @impl
             def tox_register_tox_env(register: ToxEnvRegister) -> None:
                 register.add_run_env(ExampleVirtualEnvRunner)
-    """,
-    ),
-    entry_points: dedent(
-        """
+        """,
+}
+metadata_files = {
+    entry_points: """
         [tox]
         example = {}.example_plugin""".format(
-            name,
-        ),
+        name,
     ),
     metadata: """
         Metadata-Version: 2.1
@@ -88,12 +86,22 @@ content = {
 }
 
 
-def build_wheel(wheel_directory, metadata_directory=None, config_settings=None):  # noqa: U100
+def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):  # noqa: U100
     base_name = "{}-{}-py{}-none-any.whl".format(name, version, sys.version_info[0])
     path = os.path.join(wheel_directory, base_name)
     with ZipFile(path, "w") as zip_file_handler:
         for arc_name, data in content.items():  # pragma: no branch
             zip_file_handler.writestr(arc_name, dedent(data).strip())
+        if metadata_directory is not None:
+            for sub_directory, _, filenames in os.walk(metadata_directory):
+                for filename in filenames:
+                    zip_file_handler.write(
+                        os.path.join(metadata_directory, sub_directory, filename),
+                        os.path.join(sub_directory, filename),
+                    )
+        else:
+            for arc_name, data in metadata_files.items():  # pragma: no branch
+                zip_file_handler.writestr(arc_name, dedent(data).strip())
     print("created wheel {}".format(path))
     return base_name