Fixed #27881 -- Added diffsettings --output option.

Thanks Haris Ibrahim K. V. for writng docs.

4 files changed, 74 insertions, 5 deletions

diff --git a/django/core/management/commands/diffsettings.py b/django/core/management/commands/diffsettings.py
index cc3e32b6a5..5d1621eb08 100644
--- a/django/core/management/commands/diffsettings.py
+++ b/django/core/management/commands/diffsettings.py
@@ -8,15 +8,17 @@ def module_to_dict(module, omittable=lambda k: k.startswith('_')):
 
 class Command(BaseCommand):
     help = """Displays differences between the current settings.py and Django's
-    default settings. Settings that don't appear in the defaults are
-    followed by "###"."""
+    default settings."""
 
     requires_system_checks = False
 
     def add_arguments(self, parser):
         parser.add_argument(
             '--all', action='store_true', dest='all',
-            help='Display all settings, regardless of their value. Default values are prefixed by "###".',
+            help=(
+                'Display all settings, regardless of their value. In "hash" '
+                'mode, default values are prefixed by "###".'
+            ),
         )
         parser.add_argument(
             '--default', dest='default', metavar='MODULE', default=None,
@@ -25,9 +27,18 @@ class Command(BaseCommand):
                 "compare against Django's default settings."
             ),
         )
+        parser.add_argument(
+            '--output', default='hash', choices=('hash', 'unified'), dest='output',
+            help=(
+                "Selects the output format. 'hash' mode displays each changed "
+                "setting, with the settings that don't appear in the defaults "
+                "followed by ###. 'unified' mode prefixes the default setting "
+                "with a minus sign, followed by the changed setting prefixed "
+                "with a plus sign."
+            ),
+        )
 
     def handle(self, **options):
-        # Inspired by Postfix's "postconf -n".
         from django.conf import settings, Settings, global_settings
 
         # Because settings are imported lazily, we need to explicitly load them.
@@ -36,7 +47,14 @@ class Command(BaseCommand):
         user_settings = module_to_dict(settings._wrapped)
         default = options['default']
         default_settings = module_to_dict(Settings(default) if default else global_settings)
+        output_func = {
+            'hash': self.output_hash,
+            'unified': self.output_unified,
+        }[options['output']]
+        return '\n'.join(output_func(user_settings, default_settings, **options))
 
+    def output_hash(self, user_settings, default_settings, **options):
+        # Inspired by Postfix's "postconf -n".
         output = []
         for key in sorted(user_settings):
             if key not in default_settings:
@@ -45,4 +63,16 @@ class Command(BaseCommand):
                 output.append("%s = %s" % (key, user_settings[key]))
             elif options['all']:
                 output.append("### %s = %s" % (key, user_settings[key]))
-        return '\n'.join(output)
+        return output
+
+    def output_unified(self, user_settings, default_settings, **options):
+        output = []
+        for key in sorted(user_settings):
+            if key not in default_settings:
+                output.append(self.style.SUCCESS("+ %s = %s" % (key, user_settings[key])))
+            elif user_settings[key] != default_settings[key]:
+                output.append(self.style.ERROR("- %s = %s" % (key, default_settings[key])))
+                output.append(self.style.SUCCESS("+ %s = %s" % (key, user_settings[key])))
+            elif options['all']:
+                output.append("  %s = %s" % (key, user_settings[key]))
+        return output
diff --git a/docs/ref/django-admin.txt b/docs/ref/django-admin.txt
index 68fb762623..7f120c28b3 100644
--- a/docs/ref/django-admin.txt
+++ b/docs/ref/django-admin.txt
@@ -240,6 +240,16 @@ are prefixed by ``"###"``.
 The settings module to compare the current settings against. Leave empty to
 compare against Django's default settings.
 
+.. django-admin-option:: --output {hash,unified}
+
+.. versionadded:: 2.0
+
+Specifies the output format. Available values are ``hash`` and ``unified``.
+``hash`` is the default mode that displays the output that's described above.
+``unified`` displays the output similar to ``diff -u``. Default settings are
+prefixed with a minus sign, followed by the changed setting prefixed with a
+plus sign.
+
 ``dumpdata``
 ------------
 
diff --git a/docs/releases/2.0.txt b/docs/releases/2.0.txt
index de5b38a098..ee9ae181b4 100644
--- a/docs/releases/2.0.txt
+++ b/docs/releases/2.0.txt
@@ -187,6 +187,9 @@ Management Commands
 
 * :djadmin:`loaddata` can now :ref:`read from stdin <loading-fixtures-stdin>`.
 
+* The new :option:`diffsettings --output` option allows formatting the output
+  in a unified diff format.
+
 Migrations
 ~~~~~~~~~~
 
diff --git a/tests/admin_scripts/tests.py b/tests/admin_scripts/tests.py
index fa7f9e060e..f52eac6761 100644
--- a/tests/admin_scripts/tests.py
+++ b/tests/admin_scripts/tests.py
@@ -2120,6 +2120,32 @@ class DiffSettings(AdminScriptTestCase):
         self.assertNotInOutput(out, "FOO")
         self.assertOutput(out, "BAR = 'bar2'")
 
+    def test_unified(self):
+        """--output=unified emits settings diff in unified mode."""
+        self.write_settings('settings_to_diff.py', sdict={'FOO': '"bar"'})
+        self.addCleanup(self.remove_settings, 'settings_to_diff.py')
+        args = ['diffsettings', '--settings=settings_to_diff', '--output=unified']
+        out, err = self.run_manage(args)
+        self.assertNoOutput(err)
+        self.assertOutput(out, "+ FOO = 'bar'")
+        self.assertOutput(out, "- SECRET_KEY = ''")
+        self.assertOutput(out, "+ SECRET_KEY = 'django_tests_secret_key'")
+        self.assertNotInOutput(out, "  APPEND_SLASH = True")
+
+    def test_unified_all(self):
+        """
+        --output=unified --all emits settings diff in unified mode and includes
+        settings with the default value.
+        """
+        self.write_settings('settings_to_diff.py', sdict={'FOO': '"bar"'})
+        self.addCleanup(self.remove_settings, 'settings_to_diff.py')
+        args = ['diffsettings', '--settings=settings_to_diff', '--output=unified', '--all']
+        out, err = self.run_manage(args)
+        self.assertNoOutput(err)
+        self.assertOutput(out, "  APPEND_SLASH = True")
+        self.assertOutput(out, "+ FOO = 'bar'")
+        self.assertOutput(out, "- SECRET_KEY = ''")
+
 
 class Dumpdata(AdminScriptTestCase):
     """Tests for dumpdata management command."""