Fixed #31428 -- Allowed empty message in management command self.stdout/err proxies.

django/contrib/staticfiles/management/commands/collectstatic.py

@@ -129,7 +129,7 @@ class Command(BaseCommand):
                     self.stderr.write("Post-processing '%s' failed!" % original_path)
                     # Add a blank line before the traceback, otherwise it's
                     # too easy to miss the relevant part of the error message.
-                    self.stderr.write("")
+                    self.stderr.write()
                     raise processed
                 if processed:
                     self.log("Post-processed '%s' as '%s'" %

django/core/management/base.py

@@ -137,7 +137,7 @@ class OutputWrapper(TextIOBase):
     def isatty(self):
         return hasattr(self._out, 'isatty') and self._out.isatty()
 
-    def write(self, msg, style_func=None, ending=None):
+    def write(self, msg='', style_func=None, ending=None):
         ending = self.ending if ending is None else ending
         if ending and not msg.endswith(ending):
             msg += ending

django/core/management/commands/loaddata.py

@@ -196,7 +196,7 @@ class Command(BaseCommand):
                     if obj.deferred_fields:
                         self.objs_with_deferred_fields.append(obj)
                 if objects and show_progress:
-                    self.stdout.write('')  # add a newline after progress indicator
+                    self.stdout.write()  # Add a newline after progress indicator.
                 self.loaded_object_count += loaded_objects_in_fixture
                 self.fixture_object_count += objects_in_fixture
             except Exception as e:

tests/user_commands/management/commands/hal.py

@@ -12,6 +12,7 @@ class Command(BaseCommand):
         app_labels = set(app_labels)
 
         if options['empty']:
+            self.stdout.write()
             self.stdout.write("Dave, I can't do that.")
             return
 

tests/user_commands/tests.py

@@ -124,7 +124,7 @@ class CommandTests(SimpleTestCase):
     def test_calling_a_command_with_only_empty_parameter_should_ends_gracefully(self):
         out = StringIO()
         management.call_command('hal', "--empty", stdout=out)
-        self.assertIn("Dave, I can't do that.\n", out.getvalue())
+        self.assertEqual(out.getvalue(), "\nDave, I can't do that.\n")
 
     def test_calling_command_with_app_labels_and_parameters_should_be_ok(self):
         out = StringIO()