Add build_meta_legacy backend

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``.

setuptools/build_meta.py

@@ -35,6 +35,13 @@
 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()