TST: adding isolated build test

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

Diff for: .github/workflows/ci-sage.yml

@@ -109,7 +109,7 @@ jobs:
       # Extra packages to install as system packages
       extra_sage_packages: "liblzma bzip2 libffi libpng python3 ninja_build"
       # Sage distribution packages to build
-      targets: SAGE_CHECK=no SAGE_CHECK_PACKAGES="meson_python" meson_python
+      targets: SAGE_CHECK=no SAGE_CHECK_PACKAGES="meson_python" python_build meson_python
       # Standard setting: Test the current beta release of Sage:
       sage_repo: sagemath/sage
       sage_ref: develop

Diff for: pyproject.toml

@@ -39,6 +39,7 @@ dynamic = [
 
 [project.optional-dependencies]
 test = [
+  'build',
   'pytest',
   'pytest-cov',
   'pytest-mock',

Diff for: tests/conftest.py

@@ -7,6 +7,7 @@
 import re
 import shutil
 import subprocess
+import sys
 import tempfile
 
 from venv import EnvBuilder
@@ -120,3 +121,57 @@ def fixture(tmp_dir_session):
     globals()[f'package_{normalized}'] = generate_package_fixture(package)
     globals()[f'sdist_{normalized}'] = generate_sdist_fixture(package)
     globals()[f'wheel_{normalized}'] = generate_wheel_fixture(package)
+
+
+@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,
+    )
+    return str(wheelhouse)
+
+
+@pytest.fixture
+def pep518(pep518_wheelhouse, monkeypatch):
+    monkeypatch.setenv('PIP_FIND_LINKS', pep518_wheelhouse)
+    monkeypatch.setenv('PIP_NO_INDEX', 'true')
+    return pep518_wheelhouse

Diff for: tests/test_pep518.py

@@ -0,0 +1,24 @@
+import subprocess
+import sys
+
+import pytest
+
+from .conftest import cd_package, in_git_repo_context
+
+
+@pytest.mark.parametrize(
+    ('package'),
+    [
+        'purelib-and-platlib',
+    ]
+)
+@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():
+        build_args = [build_arg] if build_arg else []
+        subprocess.run([sys.executable, '-m', 'build', f'--outdir={dist}', *build_args], cwd=package_dir, check=True)