Fixed #22738 -- Abstracted boolean field type introspection

Thanks maxi for the report, Shai Berger for his help with the patch
and Tim Graham for the review.

django/db/backends/__init__.py

@@ -614,8 +614,8 @@ class BaseDatabaseFeatures(object):
     # Can the backend introspect an BinaryField, instead of an TextField?
     can_introspect_binary_field = True
 
-    # Can the backend introspect an BooleanField, instead of an IntegerField?
-    can_introspect_boolean_field = True
+    # What is the type returned when the backend introspect a BooleanField?
+    introspected_boolean_field_type = 'BooleanField'
 
     # Can the backend introspect an DecimalField, instead of an FloatField?
     can_introspect_decimal_field = True

django/db/backends/mysql/base.py

@@ -178,7 +178,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_regex_backreferencing = False
     supports_date_lookup_using_string = False
     can_introspect_binary_field = False
-    can_introspect_boolean_field = False
+    introspected_boolean_field_type = 'IntegerField'
     can_introspect_small_integer_field = True
     supports_timezones = False
     requires_explicit_null_ordering_when_grouping = True

django/db/backends/oracle/base.py

@@ -125,6 +125,20 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     # select for update with limit can be achieved on Oracle, but not with the current backend.
     supports_select_for_update_with_limit = False
 
+    @cached_property
+    def introspected_boolean_field_type(self):
+        """
+        Some versions of Oracle -- we've seen this on 11.2.0.1 and suspect
+        it goes back -- have a weird bug where, when an integer column is
+        defined with a default, its precision is later reported on introspection
+        as 0, regardless of the real precision. For Django introspection, this
+        means that such columns are reported as IntegerField even if they are
+        really BigIntegerField or BooleanField.
+
+        The bug is solved in Oracle 11.2.0.2 and up.
+        """
+        return 'IntegerField' if self.connection.oracle_full_version < '11.2.0.2' else 'BooleanField'
+
 
 class DatabaseOperations(BaseDatabaseOperations):
     compiler_module = "django.db.backends.oracle.compiler"
@@ -735,20 +749,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         except ValueError:
             return None
 
-    @cached_property
-    def version_has_default_introspection_bug(self):
-        """
-        Some versions of Oracle -- we've seen this on 11.2.0.1 and suspect
-        it goes back -- have a weird bug where, when an integer column is
-        defined with a default, its precision is later reported on introspection
-        as 0, regardless of the real precision. For Django introspection, this
-        means that such columns are reported as IntegerField even if they are
-        really BigIntegerField or BooleanField.
-
-        The bug is solved in Oracle 11.2.0.2 and up.
-        """
-        return self.oracle_full_version < '11.2.0.2'
-
 
 class OracleParam(object):
     """

tests/inspectdb/tests.py

@@ -87,18 +87,19 @@ class InspectDBTestCase(TestCase):
         else:
             assertFieldType('big_int_field', "models.IntegerField()")
 
-        if connection.features.can_introspect_boolean_field:
+        if connection.features.introspected_boolean_field_type == 'BooleanField':
             assertFieldType('bool_field', "models.BooleanField()")
             if connection.features.can_introspect_null:
                 assertFieldType('null_bool_field', "models.NullBooleanField()")
             else:
                 assertFieldType('null_bool_field', "models.BooleanField()")
         else:
-            assertFieldType('bool_field', "models.IntegerField()")
+            field_type = connection.features.introspected_boolean_field_type
+            assertFieldType('bool_field', "models.{}()".format(field_type))
             if connection.features.can_introspect_null:
-                assertFieldType('null_bool_field', "models.IntegerField(blank=True, null=True)")
+                assertFieldType('null_bool_field', "models.{}(blank=True, null=True)".format(field_type))
             else:
-                assertFieldType('null_bool_field', "models.IntegerField()")
+                assertFieldType('null_bool_field', "models.{}()".format(field_type))
 
         if connection.features.can_introspect_decimal_field:
             assertFieldType('decimal_field', "models.DecimalField(max_digits=6, decimal_places=1)")

tests/schema/tests.py

@@ -313,15 +313,8 @@ class SchemaTests(TransactionTestCase):
         # Ensure the field is right afterwards
         columns = self.column_classes(Author)
         # BooleanField are stored as TINYINT(1) on MySQL.
-        field_type, field_info = columns['awesome']
-        if connection.vendor == 'mysql':
-            self.assertEqual(field_type, 'IntegerField')
-            self.assertEqual(field_info.precision, 1)
-        elif connection.vendor == 'oracle' and connection.version_has_default_introspection_bug:
-            self.assertEqual(field_type, 'IntegerField')
-            self.assertEqual(field_info.precision, 0)
-        else:
-            self.assertEqual(field_type, 'BooleanField')
+        field_type = columns['awesome'][0]
+        self.assertEqual(field_type, connection.features.introspected_boolean_field_type)
 
     def test_add_field_default_transform(self):
         """