Merge pull request #1652 from pganssle/build_meta_legacy

Add build_meta_legacy backend

3 files changed, 306 insertions, 214 deletions

diff --git a/changelog.d/1652.change.rst b/changelog.d/1652.change.rst
new file mode 100644
index 00000000..387d212c
--- /dev/null
+++ b/changelog.d/1652.change.rst
@@ -0,0 +1 @@
+Added the ``build_meta:__legacy__`` backend, a "compatibility mode" PEP 517 backend that can be used as the default when ``build-backend`` is left unspecified in ``pyproject.toml``.
diff --git a/setuptools/build_meta.py b/setuptools/build_meta.py
index c883d92f..70b7ab23 100644
--- a/setuptools/build_meta.py
+++ b/setuptools/build_meta.py
@@ -35,6 +35,13 @@ import contextlib
 import setuptools
 import distutils
 
+__all__ = ['get_requires_for_build_sdist',
+           'get_requires_for_build_wheel',
+           'prepare_metadata_for_build_wheel',
+           'build_wheel',
+           'build_sdist',
+           '__legacy__',
+           'SetupRequirementsError']
 
 class SetupRequirementsError(BaseException):
     def __init__(self, specifiers):
@@ -74,81 +81,11 @@ def _to_str(s):
     return s
 
 
-def _run_setup(setup_script='setup.py'):
-    # Note that we can reuse our build directory between calls
-    # Correctness comes first, then optimization later
-    __file__ = setup_script
-    __name__ = '__main__'
-    f = getattr(tokenize, 'open', open)(__file__)
-    code = f.read().replace('\\r\\n', '\\n')
-    f.close()
-    exec(compile(code, __file__, 'exec'), locals())
-
-
-def _fix_config(config_settings):
-    config_settings = config_settings or {}
-    config_settings.setdefault('--global-option', [])
-    return config_settings
-
-
-def _get_build_requires(config_settings, requirements):
-    config_settings = _fix_config(config_settings)
-
-    sys.argv = sys.argv[:1] + ['egg_info'] + \
-        config_settings["--global-option"]
-    try:
-        with Distribution.patch():
-            _run_setup()
-    except SetupRequirementsError as e:
-        requirements += e.specifiers
-
-    return requirements
-
-
 def _get_immediate_subdirectories(a_dir):
     return [name for name in os.listdir(a_dir)
             if os.path.isdir(os.path.join(a_dir, name))]
 
 
-def get_requires_for_build_wheel(config_settings=None):
-    config_settings = _fix_config(config_settings)
-    return _get_build_requires(config_settings, requirements=['wheel'])
-
-
-def get_requires_for_build_sdist(config_settings=None):
-    config_settings = _fix_config(config_settings)
-    return _get_build_requires(config_settings, requirements=[])
-
-
-def prepare_metadata_for_build_wheel(metadata_directory, config_settings=None):
-    sys.argv = sys.argv[:1] + ['dist_info', '--egg-base', _to_str(metadata_directory)]
-    _run_setup()
-
-    dist_info_directory = metadata_directory
-    while True:
-        dist_infos = [f for f in os.listdir(dist_info_directory)
-                      if f.endswith('.dist-info')]
-
-        if len(dist_infos) == 0 and \
-                len(_get_immediate_subdirectories(dist_info_directory)) == 1:
-            dist_info_directory = os.path.join(
-                dist_info_directory, os.listdir(dist_info_directory)[0])
-            continue
-
-        assert len(dist_infos) == 1
-        break
-
-    # PEP 517 requires that the .dist-info directory be placed in the
-    # metadata_directory. To comply, we MUST copy the directory to the root
-    if dist_info_directory != metadata_directory:
-        shutil.move(
-            os.path.join(dist_info_directory, dist_infos[0]),
-            metadata_directory)
-        shutil.rmtree(dist_info_directory, ignore_errors=True)
-
-    return dist_infos[0]
-
-
 def _file_with_extension(directory, extension):
     matching = (
         f for f in os.listdir(directory)
@@ -158,26 +95,137 @@ def _file_with_extension(directory, extension):
     return file
 
 
-def build_wheel(wheel_directory, config_settings=None,
-                metadata_directory=None):
-    config_settings = _fix_config(config_settings)
-    wheel_directory = os.path.abspath(wheel_directory)
-    sys.argv = sys.argv[:1] + ['bdist_wheel'] + \
-        config_settings["--global-option"]
-    _run_setup()
-    if wheel_directory != 'dist':
-        shutil.rmtree(wheel_directory)
-        shutil.copytree('dist', wheel_directory)
+class _BuildMetaBackend(object):
+
+    def _fix_config(self, config_settings):
+        config_settings = config_settings or {}
+        config_settings.setdefault('--global-option', [])
+        return config_settings
+
+    def _get_build_requires(self, config_settings, requirements):
+        config_settings = self._fix_config(config_settings)
+
+        sys.argv = sys.argv[:1] + ['egg_info'] + \
+            config_settings["--global-option"]
+        try:
+            with Distribution.patch():
+                self.run_setup()
+        except SetupRequirementsError as e:
+            requirements += e.specifiers
+
+        return requirements
+
+    def run_setup(self, setup_script='setup.py'):
+        # Note that we can reuse our build directory between calls
+        # Correctness comes first, then optimization later
+        __file__ = setup_script
+        __name__ = '__main__'
+        f = getattr(tokenize, 'open', open)(__file__)
+        code = f.read().replace('\\r\\n', '\\n')
+        f.close()
+        exec(compile(code, __file__, 'exec'), locals())
+
+    def get_requires_for_build_wheel(self, config_settings=None):
+        config_settings = self._fix_config(config_settings)
+        return self._get_build_requires(config_settings, requirements=['wheel'])
+
+    def get_requires_for_build_sdist(self, config_settings=None):
+        config_settings = self._fix_config(config_settings)
+        return self._get_build_requires(config_settings, requirements=[])
+
+    def prepare_metadata_for_build_wheel(self, metadata_directory,
+                                         config_settings=None):
+        sys.argv = sys.argv[:1] + ['dist_info', '--egg-base',
+                                   _to_str(metadata_directory)]
+        self.run_setup()
+
+        dist_info_directory = metadata_directory
+        while True:
+            dist_infos = [f for f in os.listdir(dist_info_directory)
+                          if f.endswith('.dist-info')]
+
+            if (len(dist_infos) == 0 and
+                len(_get_immediate_subdirectories(dist_info_directory)) == 1):
+
+                dist_info_directory = os.path.join(
+                    dist_info_directory, os.listdir(dist_info_directory)[0])
+                continue
+
+            assert len(dist_infos) == 1
+            break
+
+        # PEP 517 requires that the .dist-info directory be placed in the
+        # metadata_directory. To comply, we MUST copy the directory to the root
+        if dist_info_directory != metadata_directory:
+            shutil.move(
+                os.path.join(dist_info_directory, dist_infos[0]),
+                metadata_directory)
+            shutil.rmtree(dist_info_directory, ignore_errors=True)
+
+        return dist_infos[0]
+
+    def build_wheel(self, wheel_directory, config_settings=None,
+                    metadata_directory=None):
+        config_settings = self._fix_config(config_settings)
+        wheel_directory = os.path.abspath(wheel_directory)
+        sys.argv = sys.argv[:1] + ['bdist_wheel'] + \
+            config_settings["--global-option"]
+        self.run_setup()
+        if wheel_directory != 'dist':
+            shutil.rmtree(wheel_directory)
+            shutil.copytree('dist', wheel_directory)
+
+        return _file_with_extension(wheel_directory, '.whl')
+
+    def build_sdist(self, sdist_directory, config_settings=None):
+        config_settings = self._fix_config(config_settings)
+        sdist_directory = os.path.abspath(sdist_directory)
+        sys.argv = sys.argv[:1] + ['sdist', '--formats', 'gztar'] + \
+            config_settings["--global-option"] + \
+            ["--dist-dir", sdist_directory]
+        self.run_setup()
+
+        return _file_with_extension(sdist_directory, '.tar.gz')
+
+
+class _BuildMetaLegacyBackend(_BuildMetaBackend):
+    """Compatibility backend for setuptools
+
+    This is a version of setuptools.build_meta that endeavors to maintain backwards
+    compatibility with pre-PEP 517 modes of invocation. It exists as a temporary
+    bridge between the old packaging mechanism and the new packaging mechanism,
+    and will eventually be removed.
+    """
+    def run_setup(self, setup_script='setup.py'):
+        # In order to maintain compatibility with scripts assuming that
+        # the setup.py script is in a directory on the PYTHONPATH, inject
+        # '' into sys.path. (pypa/setuptools#1642)
+        sys_path = list(sys.path)           # Save the original path
+
+        script_dir = os.path.dirname(os.path.abspath(setup_script))
+        if script_dir not in sys.path:
+            sys.path.insert(0, script_dir)
+
+        try:
+            super(_BuildMetaLegacyBackend,
+                  self).run_setup(setup_script=setup_script)
+        finally:
+            # While PEP 517 frontends should be calling each hook in a fresh
+            # subprocess according to the standard (and thus it should not be
+            # strictly necessary to restore the old sys.path), we'll restore
+            # the original path so that the path manipulation does not persist
+            # within the hook after run_setup is called.
+            sys.path[:] = sys_path
 
-    return _file_with_extension(wheel_directory, '.whl')
+# The primary backend
+_BACKEND = _BuildMetaBackend()
 
+get_requires_for_build_wheel = _BACKEND.get_requires_for_build_wheel
+get_requires_for_build_sdist = _BACKEND.get_requires_for_build_sdist
+prepare_metadata_for_build_wheel = _BACKEND.prepare_metadata_for_build_wheel
+build_wheel = _BACKEND.build_wheel
+build_sdist = _BACKEND.build_sdist
 
-def build_sdist(sdist_directory, config_settings=None):
-    config_settings = _fix_config(config_settings)
-    sdist_directory = os.path.abspath(sdist_directory)
-    sys.argv = sys.argv[:1] + ['sdist', '--formats', 'gztar'] + \
-        config_settings["--global-option"] + \
-        ["--dist-dir", sdist_directory]
-    _run_setup()
 
-    return _file_with_extension(sdist_directory, '.tar.gz')
+# The legacy backend
+__legacy__ = _BuildMetaLegacyBackend()
diff --git a/setuptools/tests/test_build_meta.py b/setuptools/tests/test_build_meta.py
index 82b44c89..6236b9f4 100644
--- a/setuptools/tests/test_build_meta.py
+++ b/setuptools/tests/test_build_meta.py
@@ -6,7 +6,6 @@ import tarfile
 
 import pytest
 
-from setuptools.build_meta import build_sdist
 from .files import build_files
 from .textwrap import DALS
 from . import py2_only
@@ -24,7 +23,6 @@ class BuildBackendBase:
         self.env = env
         self.backend_name = backend_name
 
-
 class BuildBackend(BuildBackendBase):
     """PEP 517 Build Backend"""
 
@@ -44,12 +42,24 @@ class BuildBackend(BuildBackendBase):
 
 
 class BuildBackendCaller(BuildBackendBase):
+    def __init__(self, *args, **kwargs):
+        super(BuildBackendCaller, self).__init__(*args, **kwargs)
+
+        (self.backend_name, _,
+         self.backend_obj) = self.backend_name.partition(':')
+
     def __call__(self, name, *args, **kw):
         """Handles aribrary function invocations on the build backend."""
         os.chdir(self.cwd)
         os.environ.update(self.env)
         mod = importlib.import_module(self.backend_name)
-        return getattr(mod, name)(*args, **kw)
+
+        if self.backend_obj:
+            backend = getattr(mod, self.backend_obj)
+        else:
+            backend = mod
+
+        return getattr(backend, name)(*args, **kw)
 
 
 defns = [
@@ -103,136 +113,169 @@ defns = [
 ]
 
 
-@pytest.fixture(params=defns)
-def build_backend(tmpdir, request):
-    build_files(request.param, prefix=str(tmpdir))
-    with tmpdir.as_cwd():
-        yield BuildBackend(cwd='.')
-
-
-def test_get_requires_for_build_wheel(build_backend):
-    actual = build_backend.get_requires_for_build_wheel()
-    expected = ['six', 'wheel']
-    assert sorted(actual) == sorted(expected)
-
-
-def test_get_requires_for_build_sdist(build_backend):
-    actual = build_backend.get_requires_for_build_sdist()
-    expected = ['six']
-    assert sorted(actual) == sorted(expected)
-
-
-def test_build_wheel(build_backend):
-    dist_dir = os.path.abspath('pip-wheel')
-    os.makedirs(dist_dir)
-    wheel_name = build_backend.build_wheel(dist_dir)
-
-    assert os.path.isfile(os.path.join(dist_dir, wheel_name))
-
-
-def test_build_sdist(build_backend):
-    dist_dir = os.path.abspath('pip-sdist')
-    os.makedirs(dist_dir)
-    sdist_name = build_backend.build_sdist(dist_dir)
-
-    assert os.path.isfile(os.path.join(dist_dir, sdist_name))
-
-
-def test_prepare_metadata_for_build_wheel(build_backend):
-    dist_dir = os.path.abspath('pip-dist-info')
-    os.makedirs(dist_dir)
-
-    dist_info = build_backend.prepare_metadata_for_build_wheel(dist_dir)
-
-    assert os.path.isfile(os.path.join(dist_dir, dist_info, 'METADATA'))
-
-
-@py2_only
-def test_prepare_metadata_for_build_wheel_with_str(build_backend):
-    dist_dir = os.path.abspath(str('pip-dist-info'))
-    os.makedirs(dist_dir)
-
-    dist_info = build_backend.prepare_metadata_for_build_wheel(dist_dir)
-
-    assert os.path.isfile(os.path.join(dist_dir, dist_info, 'METADATA'))
-
-
-def test_build_sdist_explicit_dist(build_backend):
-    # explicitly specifying the dist folder should work
-    # the folder sdist_directory and the ``--dist-dir`` can be the same
-    dist_dir = os.path.abspath('dist')
-    sdist_name = build_backend.build_sdist(dist_dir)
-    assert os.path.isfile(os.path.join(dist_dir, sdist_name))
-
-
-def test_build_sdist_version_change(build_backend):
-    sdist_into_directory = os.path.abspath("out_sdist")
-    os.makedirs(sdist_into_directory)
-
-    sdist_name = build_backend.build_sdist(sdist_into_directory)
-    assert os.path.isfile(os.path.join(sdist_into_directory, sdist_name))
-
-    # if the setup.py changes subsequent call of the build meta
-    # should still succeed, given the
-    # sdist_directory the frontend specifies is empty
-    with open(os.path.abspath("setup.py"), 'rt') as file_handler:
-        content = file_handler.read()
-    with open(os.path.abspath("setup.py"), 'wt') as file_handler:
-        file_handler.write(
-            content.replace("version='0.0.0'", "version='0.0.1'"))
-
-    shutil.rmtree(sdist_into_directory)
-    os.makedirs(sdist_into_directory)
-
-    sdist_name = build_backend.build_sdist("out_sdist")
-    assert os.path.isfile(
-        os.path.join(os.path.abspath("out_sdist"), sdist_name))
-
-
-def test_build_sdist_setup_py_exists(tmpdir_cwd):
-    # If build_sdist is called from a script other than setup.py,
-    # ensure setup.py is include
-    build_files(defns[0])
-    targz_path = build_sdist("temp")
-    with tarfile.open(os.path.join("temp", targz_path)) as tar:
-        assert any('setup.py' in name for name in tar.getnames())
-
-
-def test_build_sdist_setup_py_manifest_excluded(tmpdir_cwd):
-    # Ensure that MANIFEST.in can exclude setup.py
-    files = {
-        'setup.py': DALS("""
-    __import__('setuptools').setup(
-        name='foo',
-        version='0.0.0',
-        py_modules=['hello']
-    )"""),
-        'hello.py': '',
-        'MANIFEST.in': DALS("""
-    exclude setup.py
-    """)
-    }
-
-    build_files(files)
-    targz_path = build_sdist("temp")
-    with tarfile.open(os.path.join("temp", targz_path)) as tar:
-        assert not any('setup.py' in name for name in tar.getnames())
-
-
-def test_build_sdist_builds_targz_even_if_zip_indicated(tmpdir_cwd):
-    files = {
+class TestBuildMetaBackend:
+    backend_name = 'setuptools.build_meta'
+
+    def get_build_backend(self):
+        return BuildBackend(cwd='.', backend_name=self.backend_name)
+
+    @pytest.fixture(params=defns)
+    def build_backend(self, tmpdir, request):
+        build_files(request.param, prefix=str(tmpdir))
+        with tmpdir.as_cwd():
+            yield self.get_build_backend()
+
+    def test_get_requires_for_build_wheel(self, build_backend):
+        actual = build_backend.get_requires_for_build_wheel()
+        expected = ['six', 'wheel']
+        assert sorted(actual) == sorted(expected)
+
+    def test_get_requires_for_build_sdist(self, build_backend):
+        actual = build_backend.get_requires_for_build_sdist()
+        expected = ['six']
+        assert sorted(actual) == sorted(expected)
+
+    def test_build_wheel(self, build_backend):
+        dist_dir = os.path.abspath('pip-wheel')
+        os.makedirs(dist_dir)
+        wheel_name = build_backend.build_wheel(dist_dir)
+
+        assert os.path.isfile(os.path.join(dist_dir, wheel_name))
+
+    def test_build_sdist(self, build_backend):
+        dist_dir = os.path.abspath('pip-sdist')
+        os.makedirs(dist_dir)
+        sdist_name = build_backend.build_sdist(dist_dir)
+
+        assert os.path.isfile(os.path.join(dist_dir, sdist_name))
+
+    def test_prepare_metadata_for_build_wheel(self, build_backend):
+        dist_dir = os.path.abspath('pip-dist-info')
+        os.makedirs(dist_dir)
+
+        dist_info = build_backend.prepare_metadata_for_build_wheel(dist_dir)
+
+        assert os.path.isfile(os.path.join(dist_dir, dist_info, 'METADATA'))
+
+    @py2_only
+    def test_prepare_metadata_for_build_wheel_with_str(self, build_backend):
+        dist_dir = os.path.abspath(str('pip-dist-info'))
+        os.makedirs(dist_dir)
+
+        dist_info = build_backend.prepare_metadata_for_build_wheel(dist_dir)
+
+        assert os.path.isfile(os.path.join(dist_dir, dist_info, 'METADATA'))
+
+    def test_build_sdist_explicit_dist(self, build_backend):
+        # explicitly specifying the dist folder should work
+        # the folder sdist_directory and the ``--dist-dir`` can be the same
+        dist_dir = os.path.abspath('dist')
+        sdist_name = build_backend.build_sdist(dist_dir)
+        assert os.path.isfile(os.path.join(dist_dir, sdist_name))
+
+    def test_build_sdist_version_change(self, build_backend):
+        sdist_into_directory = os.path.abspath("out_sdist")
+        os.makedirs(sdist_into_directory)
+
+        sdist_name = build_backend.build_sdist(sdist_into_directory)
+        assert os.path.isfile(os.path.join(sdist_into_directory, sdist_name))
+
+        # if the setup.py changes subsequent call of the build meta
+        # should still succeed, given the
+        # sdist_directory the frontend specifies is empty
+        with open(os.path.abspath("setup.py"), 'rt') as file_handler:
+            content = file_handler.read()
+        with open(os.path.abspath("setup.py"), 'wt') as file_handler:
+            file_handler.write(
+                content.replace("version='0.0.0'", "version='0.0.1'"))
+
+        shutil.rmtree(sdist_into_directory)
+        os.makedirs(sdist_into_directory)
+
+        sdist_name = build_backend.build_sdist("out_sdist")
+        assert os.path.isfile(
+            os.path.join(os.path.abspath("out_sdist"), sdist_name))
+
+    def test_build_sdist_setup_py_exists(self, tmpdir_cwd):
+        # If build_sdist is called from a script other than setup.py,
+        # ensure setup.py is included
+        build_files(defns[0])
+
+        build_backend = self.get_build_backend()
+        targz_path = build_backend.build_sdist("temp")
+        with tarfile.open(os.path.join("temp", targz_path)) as tar:
+            assert any('setup.py' in name for name in tar.getnames())
+
+    def test_build_sdist_setup_py_manifest_excluded(self, tmpdir_cwd):
+        # Ensure that MANIFEST.in can exclude setup.py
+        files = {
+            'setup.py': DALS("""
+        __import__('setuptools').setup(
+            name='foo',
+            version='0.0.0',
+            py_modules=['hello']
+        )"""),
+            'hello.py': '',
+            'MANIFEST.in': DALS("""
+        exclude setup.py
+        """)
+        }
+
+        build_files(files)
+
+        build_backend = self.get_build_backend()
+        targz_path = build_backend.build_sdist("temp")
+        with tarfile.open(os.path.join("temp", targz_path)) as tar:
+            assert not any('setup.py' in name for name in tar.getnames())
+
+    def test_build_sdist_builds_targz_even_if_zip_indicated(self, tmpdir_cwd):
+        files = {
+            'setup.py': DALS("""
+                __import__('setuptools').setup(
+                    name='foo',
+                    version='0.0.0',
+                    py_modules=['hello']
+                )"""),
+            'hello.py': '',
+            'setup.cfg': DALS("""
+                [sdist]
+                formats=zip
+                """)
+        }
+
+        build_files(files)
+
+        build_backend = self.get_build_backend()
+        build_backend.build_sdist("temp")
+
+    _relative_path_import_files = {
         'setup.py': DALS("""
             __import__('setuptools').setup(
                 name='foo',
-                version='0.0.0',
+                version=__import__('hello').__version__,
                 py_modules=['hello']
             )"""),
-        'hello.py': '',
+        'hello.py': '__version__ = "0.0.0"',
         'setup.cfg': DALS("""
             [sdist]
             formats=zip
             """)
     }
 
-    build_files(files)
-    build_sdist("temp")
+    def test_build_sdist_relative_path_import(self, tmpdir_cwd):
+        build_files(self._relative_path_import_files)
+        build_backend = self.get_build_backend()
+        with pytest.raises(ImportError):
+            build_backend.build_sdist("temp")
+
+
+class TestBuildMetaLegacyBackend(TestBuildMetaBackend):
+    backend_name = 'setuptools.build_meta:__legacy__'
+
+    # build_meta_legacy-specific tests
+    def test_build_sdist_relative_path_import(self, tmpdir_cwd):
+        # This must fail in build_meta, but must pass in build_meta_legacy
+        build_files(self._relative_path_import_files)
+
+        build_backend = self.get_build_backend()
+        build_backend.build_sdist("temp")