Revert removals introduced in v78.0.0

Author: abravalheri

setuptools/dist.py

@@ -626,21 +626,41 @@ def _enforce_underscore(self, opt: str, section: str) -> str:
         if "-" not in opt or self._skip_setupcfg_normalization(section):
             return opt
 
-        raise InvalidConfigError(
+        underscore_opt = opt.replace('-', '_')
+        affected = f"(Affected: {self.metadata.name})." if self.metadata.name else ""
+        SetuptoolsDeprecationWarning.emit(
             f"Invalid dash-separated key {opt!r} in {section!r} (setup.cfg), "
-            f"please use the underscore name {opt.replace('-', '_')!r} instead."
+            f"please use the underscore name {underscore_opt!r} instead.",
+            f"""
+            Usage of dash-separated {opt!r} will not be supported in future
+            versions. Please use the underscore name {underscore_opt!r} instead.
+            {affected}
+            """,
+            see_docs="userguide/declarative_config.html",
+            due_date=(2026, 3, 3),
             # Warning initially introduced in 3 Mar 2021
         )
+        return underscore_opt
 
     def _enforce_option_lowercase(self, opt: str, section: str) -> str:
         if opt.islower() or self._skip_setupcfg_normalization(section):
             return opt
 
-        raise InvalidConfigError(
+        lowercase_opt = opt.lower()
+        affected = f"(Affected: {self.metadata.name})." if self.metadata.name else ""
+        SetuptoolsDeprecationWarning.emit(
             f"Invalid uppercase key {opt!r} in {section!r} (setup.cfg), "
-            f"please use lowercase {opt.lower()!r} instead."
+            f"please use lowercase {lowercase_opt!r} instead.",
+            f"""
+            Usage of uppercase key {opt!r} in {section!r} will not be supported in
+            future versions. Please use lowercase {lowercase_opt!r} instead.
+            {affected}
+            """,
+            see_docs="userguide/declarative_config.html",
+            due_date=(2026, 3, 3),
             # Warning initially introduced in 6 Mar 2021
         )
+        return lowercase_opt
 
     def _skip_setupcfg_normalization(self, section: str) -> bool:
         skip = (

setuptools/tests/config/test_setupcfg.py

@@ -10,7 +10,6 @@
 
 from setuptools.config.setupcfg import ConfigHandler, Target, read_configuration
 from setuptools.dist import Distribution, _Distribution
-from setuptools.errors import InvalidConfigError
 from setuptools.warnings import SetuptoolsDeprecationWarning
 
 from ..textwrap import DALS
@@ -423,7 +422,7 @@ def test_not_utf8(self, tmpdir):
                 pass
 
     @pytest.mark.parametrize(
-        ("error_msg", "config"),
+        ("error_msg", "config", "invalid"),
         [
             (
                 "Invalid dash-separated key 'author-email' in 'metadata' (setup.cfg)",
@@ -434,6 +433,7 @@ def test_not_utf8(self, tmpdir):
                     maintainer_email = [email protected]
                     """
                 ),
+                {"author-email": "[email protected]"},
             ),
             (
                 "Invalid uppercase key 'Name' in 'metadata' (setup.cfg)",
@@ -444,14 +444,23 @@ def test_not_utf8(self, tmpdir):
                     description = Some description
                     """
                 ),
+                {"Name": "foo"},
             ),
         ],
     )
-    def test_invalid_options_previously_deprecated(self, tmpdir, error_msg, config):
-        # this test and related methods can be removed when no longer needed
+    def test_invalid_options_previously_deprecated(
+        self, tmpdir, error_msg, config, invalid
+    ):
+        # This test and related methods can be removed when no longer needed.
+        # Deprecation postponed due to push-back from the community in
+        # https://github.com/pypa/setuptools/issues/4910
         fake_env(tmpdir, config)
-        with pytest.raises(InvalidConfigError, match=re.escape(error_msg)):
-            get_dist(tmpdir).__enter__()
+        with pytest.warns(SetuptoolsDeprecationWarning, match=re.escape(error_msg)):
+            dist = get_dist(tmpdir).__enter__()
+
+        for field, value in invalid.items():
+            attr = field.replace("-", "_").lower()
+            assert getattr(dist.metadata, attr) == value
 
 
 class TestOptions: