id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
32595	mysql DatabaseSchemaEditor can't `quote_value` on byte strings	Ryan Siemens	Mariusz Felisiak	"Using the the `django.db.backends.mysql` backend with `mysqlclient` fails to render the schema migration with `sqlmigrate` when using a `BinaryField` with a binary string default value.

You can recreate this with a simple app using the following model or see the attached sample project (MD5 = 2be52a23a4001e90728d3b0f5276e087):

{{{
class TestModel(models.Model):
    ok = models.BinaryField(default=b'some-blob')
    # add this after the initial migration
    # not_ok = models.BinaryField(default=b'some-other-blob')
}}}

Then perform the following steps:

1. run initial `manage.py makemigrations`
2. uncomment the `not_ok = models.BinaryField(default=b'some-other-blob')`
3. run `manage.py makemigrations` again to generate the alter table migration
4. run `manage.py sqlmigrate <app> 0002`
5. assert the following `TypeError` is raised

{{{
Traceback (most recent call last):
  File ""manage.py"", line 22, in <module>
    main()
  File ""manage.py"", line 18, in main
    execute_from_command_line(sys.argv)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/__init__.py"", line 401, in execute_from_command_line
    utility.execute()
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/__init__.py"", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/base.py"", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/commands/sqlmigrate.py"", line 29, in execute
    return super().execute(*args, **options)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/base.py"", line 371, in execute
    output = self.handle(*args, **options)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/core/management/commands/sqlmigrate.py"", line 65, in handle
    sql_statements = loader.collect_sql(plan)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/migrations/loader.py"", line 345, in collect_sql
    state = migration.apply(state, schema_editor, collect_sql=True)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/migrations/migration.py"", line 124, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/migrations/operations/fields.py"", line 104, in database_forwards
    schema_editor.add_field(
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/backends/mysql/schema.py"", line 89, in add_field
    super().add_field(model, field)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/backends/base/schema.py"", line 487, in add_field
    self.execute(sql, params)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/backends/base/schema.py"", line 137, in execute
    self.collected_sql.append((sql % tuple(map(self.quote_value, params))) + ending)
  File ""/Users/rsiemens/sandbox/quote_value_bug/.venv/lib/python3.8/site-packages/django/db/backends/mysql/schema.py"", line 55, in quote_value
    quoted = self.connection.connection.escape(value, self.connection.connection.encoders)
TypeError: bytes() argument 2 must be str, not dict
}}}

The error seems to be raised from the mysqlclient `connection.escape`, but interestingly this works if you alter the `self.connection.connection.encoders` right before escaping (https://github.com/django/django/blob/main/django/db/backends/mysql/schema.py#L57) by doing `self.connection.connection.encoders.pop(bytes)`. Looking at the default converters mysqlclient sets up (https://github.com/PyMySQL/mysqlclient/blob/v2.0.1/MySQLdb/converters.py#L106-L139) I don't see a `bytes` one being added, so I'm guessing django adds it somewhere along the way.

Using:
Python 3.8.5
MySQL 8.0.23
Django==3.1.7
mysqlclient==2.0.3"	Bug	closed	Database layer (models, ORM)	3.1	Normal	fixed		Ryan Siemens Claude Paroz	Ready for checkin	1	0	0	0	0	0