Fixed #22172 -- Allowed index_together to be a single list (rather than list of lists)..

Thanks EmilStenstrom for the suggestion.

tests/indexes/models.py

@@ -12,6 +12,14 @@ class Article(models.Model):
         ]
 
 
+# Model for index_together being used only with single list
+class IndexTogetherSingleList(models.Model):
+    headline = models.CharField(max_length=100)
+    pub_date = models.DateTimeField()
+
+    class Meta:
+        index_together = ["headline", "pub_date"]
+
 # Indexing a TextField on Oracle or MySQL results in index creation error.
 if connection.vendor == 'postgresql':
     class IndexedArticle(models.Model):

tests/indexes/tests.py

@@ -4,7 +4,7 @@ from django.core.management.color import no_style
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.test import TestCase
 
-from .models import Article
+from .models import Article, IndexTogetherSingleList
 
 
 class IndexesTests(TestCase):
@@ -13,6 +13,12 @@ class IndexesTests(TestCase):
         index_sql = connection.creation.sql_indexes_for_model(Article, no_style())
         self.assertEqual(len(index_sql), 1)
 
+    def test_index_together_single_list(self):
+        # Test for using index_together with a single list (#22172)
+        connection = connections[DEFAULT_DB_ALIAS]
+        index_sql = connection.creation.sql_indexes_for_model(IndexTogetherSingleList, no_style())
+        self.assertEqual(len(index_sql), 1)
+
     @skipUnless(connections[DEFAULT_DB_ALIAS].vendor == 'postgresql',
         "This is a postgresql-specific issue")
     def test_postgresql_text_indexes(self):

tests/invalid_models_tests/test_models.py

@@ -45,10 +45,7 @@ class IndexTogetherTests(IsolatedModelsTestCase):
     def test_list_containing_non_iterable(self):
         class Model(models.Model):
             class Meta:
-                index_together = [
-                    'non-iterable',
-                    'second-non-iterable',
-                ]
+                index_together = [('a', 'b'), 42]
 
         errors = Model.check()
         expected = [
@@ -139,6 +136,22 @@ class UniqueTogetherTests(IsolatedModelsTestCase):
         ]
         self.assertEqual(errors, expected)
 
+    def test_non_list(self):
+        class Model(models.Model):
+            class Meta:
+                unique_together = 'not-a-list'
+
+        errors = Model.check()
+        expected = [
+            Error(
+                '"unique_together" must be a list or tuple.',
+                hint=None,
+                obj=Model,
+                id='E008',
+            ),
+        ]
+        self.assertEqual(errors, expected)
+
     def test_valid_model(self):
         class Model(models.Model):
             one = models.IntegerField()

tests/migrations/test_state.py

@@ -25,6 +25,7 @@ class StateTests(TestCase):
                 app_label = "migrations"
                 apps = new_apps
                 unique_together = ["name", "bio"]
+                index_together = ["bio", "age"]
 
         class AuthorProxy(Author):
             class Meta:
@@ -63,7 +64,7 @@ class StateTests(TestCase):
         self.assertEqual(author_state.fields[1][1].max_length, 255)
         self.assertEqual(author_state.fields[2][1].null, False)
         self.assertEqual(author_state.fields[3][1].null, True)
-        self.assertEqual(author_state.options, {"unique_together": set([("name", "bio")])})
+        self.assertEqual(author_state.options, {"unique_together": set([("name", "bio")]), "index_together": set([("bio", "age")])})
         self.assertEqual(author_state.bases, (models.Model, ))
 
         self.assertEqual(book_state.app_label, "migrations")