Fixed #29949 -- Refactored db introspection identifier converters.

Removed DatabaseIntrospection.table_name_converter()/column_name_converter()
and use instead DatabaseIntrospection.identifier_converter().

Removed DatabaseFeatures.uppercases_column_names.

Thanks Tim Graham for the initial patch and review and Simon Charette
for the review.

6 files changed, 23 insertions, 42 deletions

diff --git a/tests/backends/tests.py b/tests/backends/tests.py
index 6e6868edfb..19b46e916e 100644
--- a/tests/backends/tests.py
+++ b/tests/backends/tests.py
@@ -80,7 +80,7 @@ class ParameterHandlingTest(TestCase):
         "An executemany call with too many/not enough parameters will raise an exception (Refs #12612)"
         with connection.cursor() as cursor:
             query = ('INSERT INTO %s (%s, %s) VALUES (%%s, %%s)' % (
-                connection.introspection.table_name_converter('backends_square'),
+                connection.introspection.identifier_converter('backends_square'),
                 connection.ops.quote_name('root'),
                 connection.ops.quote_name('square')
             ))
@@ -217,7 +217,7 @@ class BackendTestCase(TransactionTestCase):
 
     def create_squares(self, args, paramstyle, multiple):
         opts = Square._meta
-        tbl = connection.introspection.table_name_converter(opts.db_table)
+        tbl = connection.introspection.identifier_converter(opts.db_table)
         f1 = connection.ops.quote_name(opts.get_field('root').column)
         f2 = connection.ops.quote_name(opts.get_field('square').column)
         if paramstyle == 'format':
@@ -303,7 +303,7 @@ class BackendTestCase(TransactionTestCase):
                 'SELECT %s, %s FROM %s ORDER BY %s' % (
                     qn(f3.column),
                     qn(f4.column),
-                    connection.introspection.table_name_converter(opts2.db_table),
+                    connection.introspection.identifier_converter(opts2.db_table),
                     qn(f3.column),
                 )
             )
diff --git a/tests/constraints/tests.py b/tests/constraints/tests.py
index ddcaf7cfe0..d53892c3a3 100644
--- a/tests/constraints/tests.py
+++ b/tests/constraints/tests.py
@@ -48,8 +48,6 @@ class CheckConstraintTests(TestCase):
     def test_name(self):
         constraints = get_constraints(Product._meta.db_table)
         expected_name = 'price_gt_discounted_price'
-        if connection.features.uppercases_column_names:
-            expected_name = expected_name.upper()
         self.assertIn(expected_name, constraints)
 
 
@@ -87,6 +85,4 @@ class UniqueConstraintTests(TestCase):
     def test_name(self):
         constraints = get_constraints(Product._meta.db_table)
         expected_name = 'unique_name'
-        if connection.features.uppercases_column_names:
-            expected_name = expected_name.upper()
         self.assertIn(expected_name, constraints)
diff --git a/tests/gis_tests/gis_migrations/test_operations.py b/tests/gis_tests/gis_migrations/test_operations.py
index 3694a7eb67..c5794eebc2 100644
--- a/tests/gis_tests/gis_migrations/test_operations.py
+++ b/tests/gis_tests/gis_migrations/test_operations.py
@@ -63,12 +63,9 @@ class OperationTestCase(TransactionTestCase):
         self.current_state = self.apply_operations('gis', ProjectState(), operations)
 
     def assertGeometryColumnsCount(self, expected_count):
-        table_name = 'gis_neighborhood'
-        if connection.features.uppercases_column_names:
-            table_name = table_name.upper()
         self.assertEqual(
             GeometryColumns.objects.filter(**{
-                GeometryColumns.table_name_col(): table_name,
+                '%s__iexact' % GeometryColumns.table_name_col(): 'gis_neighborhood',
             }).count(),
             expected_count
         )
diff --git a/tests/inspectdb/tests.py b/tests/inspectdb/tests.py
index b578dbf3df..6452002c3e 100644
--- a/tests/inspectdb/tests.py
+++ b/tests/inspectdb/tests.py
@@ -184,7 +184,7 @@ class InspectDBTestCase(TestCase):
         out = StringIO()
         call_command('inspectdb', table_name_filter=special_table_only, stdout=out)
         output = out.getvalue()
-        base_name = 'field' if connection.features.uppercases_column_names else 'Field'
+        base_name = connection.introspection.identifier_converter('Field')
         self.assertIn("field = models.IntegerField()", output)
         self.assertIn("field_field = models.IntegerField(db_column='%s_')" % base_name, output)
         self.assertIn("field_field_0 = models.IntegerField(db_column='%s__')" % base_name, output)
diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 6f2b6df765..fc39b77f87 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -85,7 +85,7 @@ class SchemaTests(TransactionTestCase):
 
     def delete_tables(self):
         "Deletes all model tables for our models for a clean test environment"
-        converter = connection.introspection.table_name_converter
+        converter = connection.introspection.identifier_converter
         with connection.schema_editor() as editor:
             connection.disable_constraint_checking()
             table_names = connection.introspection.table_names()
@@ -1868,9 +1868,6 @@ class SchemaTests(TransactionTestCase):
                 table_name=AuthorWithIndexedName._meta.db_table,
                 column_names=('name',),
             )
-        if connection.features.uppercases_column_names:
-            author_index_name = author_index_name.upper()
-            db_index_name = db_index_name.upper()
         try:
             AuthorWithIndexedName._meta.indexes = [index]
             with connection.schema_editor() as editor:
@@ -1908,8 +1905,6 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor() as editor:
             editor.add_index(Author, index)
         if connection.features.supports_index_column_ordering:
-            if connection.features.uppercases_column_names:
-                index_name = index_name.upper()
             self.assertIndexOrder(Author._meta.db_table, index_name, ['ASC', 'DESC'])
         # Drop the index
         with connection.schema_editor() as editor:
@@ -2122,12 +2117,14 @@ class SchemaTests(TransactionTestCase):
         field = get_field()
         table = model._meta.db_table
         column = field.column
+        identifier_converter = connection.introspection.identifier_converter
 
         with connection.schema_editor() as editor:
             editor.create_model(model)
             editor.add_field(model, field)
 
-            constraint_name = "CamelCaseIndex"
+            constraint_name = 'CamelCaseIndex'
+            expected_constraint_name = identifier_converter(constraint_name)
             editor.execute(
                 editor.sql_create_index % {
                     "table": editor.quote_name(table),
@@ -2138,22 +2135,20 @@ class SchemaTests(TransactionTestCase):
                     "condition": "",
                 }
             )
-            if connection.features.uppercases_column_names:
-                constraint_name = constraint_name.upper()
-            self.assertIn(constraint_name, self.get_constraints(model._meta.db_table))
+            self.assertIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
             editor.alter_field(model, get_field(db_index=True), field, strict=True)
-            self.assertNotIn(constraint_name, self.get_constraints(model._meta.db_table))
+            self.assertNotIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
 
-            constraint_name = "CamelCaseUniqConstraint"
+            constraint_name = 'CamelCaseUniqConstraint'
+            expected_constraint_name = identifier_converter(constraint_name)
             editor.execute(editor._create_unique_sql(model, [field.column], constraint_name))
-            if connection.features.uppercases_column_names:
-                constraint_name = constraint_name.upper()
-            self.assertIn(constraint_name, self.get_constraints(model._meta.db_table))
+            self.assertIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
             editor.alter_field(model, get_field(unique=True), field, strict=True)
-            self.assertNotIn(constraint_name, self.get_constraints(model._meta.db_table))
+            self.assertNotIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
 
             if editor.sql_foreign_key_constraint:
-                constraint_name = "CamelCaseFKConstraint"
+                constraint_name = 'CamelCaseFKConstraint'
+                expected_constraint_name = identifier_converter(constraint_name)
                 fk_sql = editor.sql_foreign_key_constraint % {
                     "column": editor.quote_name(column),
                     "to_table": editor.quote_name(table),
@@ -2170,11 +2165,9 @@ class SchemaTests(TransactionTestCase):
                         "constraint": constraint_sql,
                     }
                 )
-                if connection.features.uppercases_column_names:
-                    constraint_name = constraint_name.upper()
-                self.assertIn(constraint_name, self.get_constraints(model._meta.db_table))
+                self.assertIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
                 editor.alter_field(model, get_field(Author, CASCADE, field_class=ForeignKey), field, strict=True)
-                self.assertNotIn(constraint_name, self.get_constraints(model._meta.db_table))
+                self.assertNotIn(expected_constraint_name, self.get_constraints(model._meta.db_table))
 
     def test_add_field_use_effective_default(self):
         """
@@ -2491,11 +2484,7 @@ class SchemaTests(TransactionTestCase):
         new_field.set_attributes_from_name('weight')
         with connection.schema_editor() as editor:
             editor.alter_field(Author, old_field, new_field, strict=True)
-
-        expected = 'schema_author_weight_587740f9'
-        if connection.features.uppercases_column_names:
-            expected = expected.upper()
-        self.assertEqual(self.get_constraints_for_column(Author, 'weight'), [expected])
+        self.assertEqual(self.get_constraints_for_column(Author, 'weight'), ['schema_author_weight_587740f9'])
 
         # Remove db_index=True to drop index.
         with connection.schema_editor() as editor:
diff --git a/tests/select_for_update/tests.py b/tests/select_for_update/tests.py
index a750dc61db..f359dc2650 100644
--- a/tests/select_for_update/tests.py
+++ b/tests/select_for_update/tests.py
@@ -113,11 +113,10 @@ class SelectForUpdateTests(TransactionTestCase):
             ))
         features = connections['default'].features
         if features.select_for_update_of_column:
-            expected = ['"select_for_update_person"."id"', '"select_for_update_country"."id"']
+            expected = ['select_for_update_person"."id', 'select_for_update_country"."id']
         else:
-            expected = ['"select_for_update_person"', '"select_for_update_country"']
-        if features.uppercases_column_names:
-            expected = [value.upper() for value in expected]
+            expected = ['select_for_update_person', 'select_for_update_country']
+        expected = [connection.ops.quote_name(value) for value in expected]
         self.assertTrue(self.has_for_update_sql(ctx.captured_queries, of=expected))
 
     @skipUnlessDBFeature('has_select_for_update_of')