inspection.info: simplify get_pep517_metadata

Signed-off-by: Filipe Laíns <[email protected]>

src/poetry/inspection/info.py

@@ -4,15 +4,17 @@
 import functools
 import glob
 import logging
-import os
+import re
 import tarfile
 import zipfile
 
 from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import Any
 
+import build
 import pkginfo
+import pyproject_hooks
 
 from poetry.core.factory import Factory
 from poetry.core.packages.dependency import Dependency
@@ -38,28 +40,6 @@
 
 logger = logging.getLogger(__name__)
 
-PEP517_META_BUILD = """\
-import build
-import build.env
-import pyproject_hooks
-
-source = '{source}'
-dest = '{dest}'
-
-with build.env.IsolatedEnvBuilder() as env:
-    builder = build.ProjectBuilder(
-        srcdir=source,
-        scripts_dir=env.scripts_dir,
-        python_executable=env.executable,
-        runner=pyproject_hooks.quiet_subprocess_runner,
-    )
-    env.install(builder.build_system_requires)
-    env.install(builder.get_requires_for_build('wheel'))
-    builder.metadata_path(dest)
-"""
-
-PEP517_META_BUILD_DEPS = ["build==0.9.0", "pyproject_hooks==1.0.0"]
-
 
 class PackageInfoError(ValueError):
     def __init__(self, path: Path | str, *reasons: BaseException | str) -> None:
@@ -565,72 +545,95 @@ def from_path(cls, path: Path) -> PackageInfo:
             return cls.from_sdist(path=path)
 
 
-@functools.lru_cache(maxsize=None)
-def get_pep517_metadata(path: Path) -> PackageInfo:
-    """
-    Helper method to use PEP-517 library to build and read package metadata.
-
-    :param path: Path to package source to build and read metadata for.
-    """
-    info = None
-
-    with contextlib.suppress(PackageInfoError):
-        info = PackageInfo.from_setup_files(path)
-        if all([info.version, info.name, info.requires_dist]):
-            return info
-
+def _get_pep517_metadata_from_backend(path: Path) -> PackageInfo | None:
     with ephemeral_environment(
         flags={"no-pip": False, "no-setuptools": False, "no-wheel": False}
     ) as venv:
         # TODO: cache PEP 517 build environment corresponding to each project venv
         dest_dir = venv.path.parent / "dist"
         dest_dir.mkdir()
 
-        pep517_meta_build_script = PEP517_META_BUILD.format(
-            source=path.as_posix(), dest=dest_dir.as_posix()
+        builder = build.ProjectBuilder(
+            source_dir=path,
+            python_executable=venv.python,
+            runner=pyproject_hooks.quiet_subprocess_runner,
         )
 
+        # install build backend dependencies
         try:
-            venv.run_pip(
-                "install",
-                "--disable-pip-version-check",
-                "--ignore-installed",
-                "--no-input",
-                *PEP517_META_BUILD_DEPS,
-            )
-            venv.run(
-                "python",
-                "-",
-                input_=pep517_meta_build_script,
-            )
-            info = PackageInfo.from_metadata(dest_dir)
+            # install build system dependencies first
+            venv.run_pip_install(*builder.build_system_requires)
+            # then install extra dependencies needed to build a wheel
+            # (this needs to be done in a separate step because we need the
+            #  build system dependencies to run the backend)
+            venv.run_pip_install(*builder.get_requires_for_build("wheel"))
         except EnvCommandError as e:
-            # something went wrong while attempting pep517 metadata build
-            # fallback to egg_info if setup.py available
-            logger.debug("PEP517 build failed: %s", e)
-            setup_py = path / "setup.py"
-            if not setup_py.exists():
-                raise PackageInfoError(
-                    path,
-                    e,
-                    "No fallback setup.py file was found to generate egg_info.",
-                )
+            # if it's a legacy project (uses setuptools), the dependencies
+            # should already be met, as we set no-setuptools=False, so the pip
+            # install calls should never fail. if they do, it means there really
+            # is a missing build dependency, and pip wasn't able to install it.
+            # we should simply return an error in this case.
+            raise PackageInfoError(
+                path, "Failed to provision the build environment.", e
+            )
 
-            cwd = Path.cwd()
-            os.chdir(path.as_posix())
+        # try the prepare_metadata_for_build_wheel hook
+        metadata = builder.prepare("wheel", dest_dir)
+        if metadata:
+            logger.debug("got metadata from prepare_metadata_for_build_wheel")
+            return PackageInfo.from_metadata(dest_dir)
+
+        logger.debug("prepare_metadata_for_build_wheel failed or it's not supported")
+
+        # next, try setup.py egg_info if setup.py exists
+        setup_py = path / "setup.py"
+        if setup_py.is_file():
             try:
                 venv.run("python", "setup.py", "egg_info")
-                info = PackageInfo.from_metadata(path)
-            except EnvCommandError as fbe:
-                raise PackageInfoError(
-                    path, "Fallback egg_info generation failed.", fbe
+            except EnvCommandError as e:
+                logger.debug("setup.py egg_info failed: %s", e)
+            else:
+                return PackageInfo.from_metadata(builder.metadata_path(path))
+
+        # finally, try the build_wheel hook
+        wheel_name = builder.build("wheel", dest_dir)
+        if wheel_name:
+            with zipfile.ZipFile(dest_dir / wheel_name) as w:
+                # extract the .dist_info directory
+                w.extractall(
+                    dest_dir,
+                    (
+                        member
+                        for member in w.filelist()
+                        if re.match(r".*\.dist-info\/", member)
+                    ),
                 )
-            finally:
-                os.chdir(cwd.as_posix())
+            logger.debug("got metadata from build_wheel")
+            return PackageInfo.from_metadata(dest_dir)
+
+        logger.debug("build_wheel failed")
+
+
+
+@functools.lru_cache(maxsize=None)
+def get_pep517_metadata(path: Path) -> PackageInfo:
+    """
+    Helper method to use PEP-517 library to build and read package metadata.
+
+    :param path: Path to package source to build and read metadata for.
+    """
+    info = None
+
+    with contextlib.suppress(PackageInfoError):
+        info = PackageInfo.from_setup_files(path)
+        if all([info.version, info.name, info.requires_dist]):
+            return info
+
+    # try fetching the metadata from the backend, but fall back to reading
+    # from the setup files (PackageInfo.from_setup_files) if we fail
+    info = _get_pep517_metadata_from_backend(path) or info
 
     if info:
-        logger.debug("Falling back to parsed setup.py file for %s", path)
         return info
 
-    # if we reach here, everything has failed and all hope is lost
     raise PackageInfoError(path, "Exhausted all core metadata sources.")