bpo-19610: Warn if distutils is provided something other than a list to some fields (#4685)

* Rather than raise TypeError, warn and call list() on the value.

* Fix tests, revise NEWS and whatsnew text.

* Revise documentation, a string is okay as well.

* Ensure 'requires' and 'obsoletes' are real lists.

* Test that requires and obsoletes are turned to lists.

1 files changed, 38 insertions, 10 deletions

diff --git a/Lib/distutils/tests/test_dist.py b/Lib/distutils/tests/test_dist.py
index 50b456e..0a19f0f 100644
--- a/Lib/distutils/tests/test_dist.py
+++ b/Lib/distutils/tests/test_dist.py
@@ -11,7 +11,9 @@ from unittest import mock
 from distutils.dist import Distribution, fix_help_options, DistributionMetadata
 from distutils.cmd import Command
 
-from test.support import TESTFN, captured_stdout, run_unittest
+from test.support import (
+     TESTFN, captured_stdout, captured_stderr, run_unittest
+)
 from distutils.tests import support
 from distutils import log
 
@@ -319,6 +321,13 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
                            "version": "1.0",
                            "requires": ["my.pkg (splat)"]})
 
+    def test_requires_to_list(self):
+        attrs = {"name": "package",
+                 "requires": iter(["other"])}
+        dist = Distribution(attrs)
+        self.assertIsInstance(dist.metadata.requires, list)
+
+
     def test_obsoletes(self):
         attrs = {"name": "package",
                  "version": "1.0",
@@ -341,6 +350,12 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
                            "version": "1.0",
                            "obsoletes": ["my.pkg (splat)"]})
 
+    def test_obsoletes_to_list(self):
+        attrs = {"name": "package",
+                 "obsoletes": iter(["other"])}
+        dist = Distribution(attrs)
+        self.assertIsInstance(dist.metadata.obsoletes, list)
+
     def test_classifier(self):
         attrs = {'name': 'Boa', 'version': '3.0',
                  'classifiers': ['Programming Language :: Python :: 3']}
@@ -353,9 +368,14 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
     def test_classifier_invalid_type(self):
         attrs = {'name': 'Boa', 'version': '3.0',
                  'classifiers': ('Programming Language :: Python :: 3',)}
-        msg = "'classifiers' should be a 'list', not 'tuple'"
-        with self.assertRaises(TypeError, msg=msg):
-            Distribution(attrs)
+        with captured_stderr() as error:
+            d = Distribution(attrs)
+        # should have warning about passing a non-list
+        self.assertIn('should be a list', error.getvalue())
+        # should be converted to a list
+        self.assertIsInstance(d.metadata.classifiers, list)
+        self.assertEqual(d.metadata.classifiers,
+                         list(attrs['classifiers']))
 
     def test_keywords(self):
         attrs = {'name': 'Monty', 'version': '1.0',
@@ -367,9 +387,13 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
     def test_keywords_invalid_type(self):
         attrs = {'name': 'Monty', 'version': '1.0',
                  'keywords': ('spam', 'eggs', 'life of brian')}
-        msg = "'keywords' should be a 'list', not 'tuple'"
-        with self.assertRaises(TypeError, msg=msg):
-            Distribution(attrs)
+        with captured_stderr() as error:
+            d = Distribution(attrs)
+        # should have warning about passing a non-list
+        self.assertIn('should be a list', error.getvalue())
+        # should be converted to a list
+        self.assertIsInstance(d.metadata.keywords, list)
+        self.assertEqual(d.metadata.keywords, list(attrs['keywords']))
 
     def test_platforms(self):
         attrs = {'name': 'Monty', 'version': '1.0',
@@ -381,9 +405,13 @@ class MetadataTestCase(support.TempdirManager, support.EnvironGuard,
     def test_platforms_invalid_types(self):
         attrs = {'name': 'Monty', 'version': '1.0',
                  'platforms': ('GNU/Linux', 'Some Evil Platform')}
-        msg = "'platforms' should be a 'list', not 'tuple'"
-        with self.assertRaises(TypeError, msg=msg):
-            Distribution(attrs)
+        with captured_stderr() as error:
+            d = Distribution(attrs)
+        # should have warning about passing a non-list
+        self.assertIn('should be a list', error.getvalue())
+        # should be converted to a list
+        self.assertIsInstance(d.metadata.platforms, list)
+        self.assertEqual(d.metadata.platforms, list(attrs['platforms']))
 
     def test_download_url(self):
         attrs = {'name': 'Boa', 'version': '3.0',