Ignore newlines when processing keywords/platforms

Newlines in `keywords` or `platforms` can break
the produced metadata in PKG-INFO or METADATA files.

Fixes: pypa/setuptools#4887

Author: frenzymadness

distutils/dist.py

@@ -644,6 +644,7 @@ def finalize_options(self) -> None:
             if value is None:
                 continue
             if isinstance(value, str):
+                value = value.replace("\n", " ")
                 value = [elm.strip() for elm in value.split(',')]
                 setattr(self.metadata, attr, value)
 

distutils/tests/test_dist.py

@@ -217,6 +217,19 @@ def test_finalize_options(self):
         assert dist.metadata.platforms == ['foo bar']
         assert dist.metadata.keywords == ['foo bar']
 
+        # finalize_option removes '\n' from keywords and platforms
+        attrs = {'keywords': 'one,two,\nthree,four\n', 'platforms': 'one,two,\nthree,four\n'}
+        dist = Distribution(attrs=attrs)
+        dist.finalize_options()
+        assert dist.metadata.platforms == ['one', 'two', 'three', 'four']
+        assert dist.metadata.keywords == ['one', 'two', 'three', 'four']
+
+        attrs = {'keywords': 'one two\nthree four\n', 'platforms': 'one two\nthree four\n'}
+        dist = Distribution(attrs=attrs)
+        dist.finalize_options()
+        assert dist.metadata.platforms == ['one two three four']
+        assert dist.metadata.keywords == ['one two three four']
+
     def test_get_command_packages(self):
         dist = Distribution()
         assert dist.command_packages is None