Add _supported_features()

dev-requirements.txt

@@ -1,5 +1,6 @@
 pytest
 pytest-flake8
+flake8 < 4  # https://github.com/tholo/pytest-flake8/issues/81
 pytest-forward-compatibility; python_version<'3'
 mock ; python_version<'3.6'
 testpath

pep517/in_process/_in_process.py

@@ -103,6 +103,19 @@ def _build_backend():
     return obj
 
 
+def _supported_features():
+    """Return the list of options features supported by the backend.
+
+    Returns a list of strings.
+    The only possible value is 'build_editable'.
+    """
+    backend = _build_backend()
+    features = []
+    if hasattr(backend, "build_editable"):
+        features.append("build_editable")
+    return features
+
+
 def get_requires_for_build_wheel(config_settings):
     """Invoke the optional get_requires_for_build_wheel hook
 
@@ -312,6 +325,7 @@ def build_sdist(sdist_directory, config_settings):
     'build_editable',
     'get_requires_for_build_sdist',
     'build_sdist',
+    '_supported_features',
 }
 
 

pep517/wrappers.py

@@ -154,6 +154,10 @@ def subprocess_runner(self, runner):
         finally:
             self._subprocess_runner = prev
 
+    def _supported_features(self):
+        """Return the list of optional features supported by the backend."""
+        return self._call_hook('_supported_features', {})
+
     def get_requires_for_build_wheel(self, config_settings=None):
         """Identify packages required for building a wheel
 

tests/test_call_hooks.py

@@ -211,3 +211,18 @@ def test_setup_py():
     # Some versions of setuptools list setuptools itself here
     res = [x for x in res if x != 'setuptools']
     assert res == ['wheel']
+
+
+@pytest.mark.parametrize(
+    ("pkg", "expected"),
+    [
+        ("pkg1", ["build_editable"]),
+        ("pkg2", []),
+        ("pkg3", ["build_editable"]),
+    ],
+)
+def test__supported_features(pkg, expected):
+    hooks = get_hooks(pkg)
+    with modified_env({"PYTHONPATH": BUILDSYS_PKGS}):
+        res = hooks._supported_features()
+    assert res == expected