Fix previous detection of empty arrays

setuptools/config/_apply_pyprojecttoml.py

@@ -303,7 +303,7 @@ def _some_attrgetter(*items):
     """
     def _acessor(obj):
         values = (_attrgetter(i)(obj) for i in items)
-        return next((i for i in values if i), None)
+        return next((i for i in values if i is not None), None)
     return _acessor
 
 

setuptools/config/pyprojecttoml.py

@@ -282,11 +282,12 @@ def _expand_all_dynamic(self, dist: "Distribution", package_dir: Mapping[str, st
         )
         # `None` indicates there is nothing in `tool.setuptools.dynamic` but the value
         # might have already been set by setup.py/extensions, so avoid overwriting.
-        self.project_cfg.update({k: v for k, v in obtained_dynamic.items() if v})
+        updates = {k: v for k, v in obtained_dynamic.items() if v is not None}
+        self.project_cfg.update(updates)
 
     def _ensure_previously_set(self, dist: "Distribution", field: str):
         previous = _PREVIOUSLY_DEFINED[field](dist)
-        if not previous and not self.ignore_option_errors:
+        if previous is None and not self.ignore_option_errors:
             msg = (
                 f"No configuration found for dynamic {field!r}.\n"
                 "Some dynamic fields need to be specified via `tool.setuptools.dynamic`"

setuptools/tests/config/test_apply_pyprojecttoml.py

@@ -14,7 +14,7 @@
 from setuptools.dist import Distribution
 from setuptools.config import setupcfg, pyprojecttoml
 from setuptools.config import expand
-from setuptools.config._apply_pyprojecttoml import _WouldIgnoreField
+from setuptools.config._apply_pyprojecttoml import _WouldIgnoreField, _some_attrgetter
 from setuptools.command.egg_info import write_requirements
 
 
@@ -234,12 +234,14 @@ def test_not_listed_in_dynamic(self, tmp_path, attr, field, value):
             dist = pyprojecttoml.apply_configuration(dist, pyproject)
 
         # TODO: Once support for pyproject.toml config stabilizes attr should be None
-        dist_value = getattr(dist, attr, None) or getattr(dist.metadata, attr, object())
+        dist_value = _some_attrgetter(f"metadata.{attr}", attr)(dist)
         assert dist_value == value
 
     @pytest.mark.parametrize(
         "attr, field, value",
         [
+            ("install_requires", "dependencies", []),
+            ("extras_require", "optional-dependencies", {}),
             ("install_requires", "dependencies", ["six"]),
             ("classifiers", "classifiers", ["Private :: Classifier"]),
         ]
@@ -248,7 +250,7 @@ def test_listed_in_dynamic(self, tmp_path, attr, field, value):
         pyproject = self.pyproject(tmp_path, [field])
         dist = makedist(tmp_path, **{attr: value})
         dist = pyprojecttoml.apply_configuration(dist, pyproject)
-        dist_value = getattr(dist, attr, None) or getattr(dist.metadata, attr, object())
+        dist_value = _some_attrgetter(f"metadata.{attr}", attr)(dist)
         assert dist_value == value
 
     def test_optional_dependencies_dont_remove_env_markers(self, tmp_path):