Fixed #24846 -- Added support to MySQL SchemaEditor for all blob/text data types

AUTHORS

@@ -8,6 +8,7 @@ answer newbie questions, and generally made Django that much better:
     Aaron Cannon <cannona@fireantproductions.com>
     Aaron Swartz <http://www.aaronsw.com/>
     Aaron T. Myers <atmyers@gmail.com>
+    Adam Johnson <https://github.com/adamchainz>
     Adam Vandenberg
     Adrian Holovaty <adrian@holovaty.com>
     Adrien Lemaire <lemaire.adrien@gmail.com>

django/db/backends/mysql/schema.py

@@ -34,10 +34,17 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
 
     def skip_default(self, field):
         """
-        MySQL doesn't accept default values for longtext and longblob
+        MySQL doesn't accept default values for TEXT and BLOB types, and
-        and implicitly treats these columns as nullable.
+        implicitly treats these columns as nullable.
         """
-        return field.db_type(self.connection) in {'longtext', 'longblob'}
+        db_type = field.db_type(self.connection)
+        return (
+            db_type is not None and
+            db_type.lower() in {
+                'tinyblob', 'blob', 'mediumblob', 'longblob',
+                'tinytext', 'text', 'mediumtext', 'longtext',
+            }
+        )
 
     def add_field(self, model, field):
         super(DatabaseSchemaEditor, self).add_field(model, field)

tests/schema/fields.py

@@ -1,3 +1,4 @@
+from django.db import models
 from django.db.models.fields.related import (
     RECURSIVE_RELATIONSHIP_CONSTANT, ManyRelatedObjectsDescriptor,
     ManyToManyField, ManyToManyRel, RelatedField,
@@ -56,3 +57,11 @@ class CustomManyToManyField(RelatedField):
 
 class InheritedManyToManyField(ManyToManyField):
     pass
+
+
+class MediumBlobField(models.BinaryField):
+    """
+    A MySQL BinaryField that uses a different blob size.
+    """
+    def db_type(self, connection):
+        return 'MEDIUMBLOB'

tests/schema/tests.py

@@ -17,7 +17,9 @@ from django.db.models.fields.related import (
 from django.db.transaction import atomic
 from django.test import TransactionTestCase, skipIfDBFeature
 
-from .fields import CustomManyToManyField, InheritedManyToManyField
+from .fields import (
+    CustomManyToManyField, InheritedManyToManyField, MediumBlobField,
+)
 from .models import (
     Author, AuthorWithDefaultHeight, AuthorWithEvenLongerName, Book, BookWeak,
     BookWithLongName, BookWithO2O, BookWithSlug, Note, NoteRename, Tag,
@@ -383,6 +385,23 @@ class SchemaTests(TransactionTestCase):
         # these two types.
         self.assertIn(columns['bits'][0], ("BinaryField", "TextField"))
 
+    @unittest.skipUnless(connection.vendor == 'mysql', "MySQL specific")
+    def test_add_binaryfield_mediumblob(self):
+        """
+        Test adding a custom-sized binary field on MySQL (#24846).
+        """
+        # Create the table
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+        # Add the new field with default
+        new_field = MediumBlobField(blank=True, default=b'123')
+        new_field.set_attributes_from_name('bits')
+        with connection.schema_editor() as editor:
+            editor.add_field(Author, new_field)
+        columns = self.column_classes(Author)
+        # Introspection treats BLOBs as TextFields
+        self.assertEqual(columns['bits'][0], "TextField")
+
     def test_alter(self):
         """
         Tests simple altering of fields