TST: simplify pep518 test setup

This also makes the test work on Cygwin where a ninja wheel is not
available and needs to be built from the source distribution.

Author: dnicolodi

tests/conftest.py

@@ -126,47 +126,17 @@ def fixture(tmp_dir_session):
 @pytest.fixture(scope='session')
 def pep518_wheelhouse(tmpdir_factory):
     wheelhouse = tmpdir_factory.mktemp('wheelhouse')
-    dist = tmpdir_factory.mktemp('dist')
-    subprocess.run(
-        [sys.executable, '-m', 'build', '--wheel', '--outdir', str(dist)],
-        cwd=str(package_dir.parent.parent),
-        check=True,
-    )
-    (wheel_path,) = dist.visit('*.whl')
-    subprocess.run(
-        [
-            sys.executable,
-            '-m',
-            'pip',
-            'download',
-            '-q',
-            '-d',
-            str(wheelhouse),
-            str(wheel_path),
-        ],
-        check=True,
-    )
-    subprocess.run(
-        [
-            sys.executable,
-            '-m',
-            'pip',
-            'download',
-            '-q',
-            '-d',
-            str(wheelhouse),
-            'build',
-            'colorama',
-            'meson',
-            'ninja',
-            'patchelf',
-            'pyproject-metadata',
-            'tomli',
-            'typing-extensions',
-            'wheel',
-        ],
-        check=True,
-    )
+    meson_python = str(package_dir.parent.parent)
+    # Populate wheelhouse with wheel for the following packages and
+    # their dependencies.  Wheels are downloaded from PyPI or built
+    # from the source distribution as needed.  Sources or wheels in
+    # the pip cache are used when available.
+    packages = [
+        meson_python,
+        'build',
+        'wheel',
+    ]
+    subprocess.check_call([sys.executable, '-m', 'pip', 'wheel', '--wheel-dir', str(wheelhouse), *packages])
     return str(wheelhouse)
 
 

tests/test_pep518.py

@@ -15,10 +15,9 @@
 @pytest.mark.parametrize(
     'build_arg', ['', '--wheel'], ids=['sdist_to_wheel', 'wheel_directly']
 )
-@pytest.mark.xfail(sys.platform.startswith('cygwin'), reason='ninja pip package not available on cygwin', strict=True)
 def test_pep518(pep518, package, build_arg, tmp_path):
     dist = tmp_path / 'dist'
 
-    with cd_package(package) as package_dir, in_git_repo_context():
+    with cd_package(package), in_git_repo_context():
         build_args = [build_arg] if build_arg else []
-        subprocess.run([sys.executable, '-m', 'build', f'--outdir={dist}', *build_args], cwd=package_dir, check=True)
+        subprocess.check_call([sys.executable, '-m', 'build', '--outdir', str(dist), *build_args])