#31245: "Invalid default value for '<charfield>'" for CharField choices
migration
generated by Django 1.11 and run on Django 2.2
-----------------------------------------+------------------------
Reporter: Tony S Yu | Owner: nobody
Type: Bug | Status: new
Component: Uncategorized | Version: 2.2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-----------------------------------------+------------------------
= System details =
- Migrations generated in Django 1.11.28 + Python 2.7
- Migrations run on Django 2.2.10 + Python 3.6
- Database backend: `django.db.backends.mysql`
= Summary =
We recently upgraded an app from Django 1.11 to 2.2. When a developer on
the team attempted to re-install the app from scratch some time later,
they ran into the following exception:
{{{
django.db.utils.OperationalError: (1067, "Invalid default value for
'<charfield>'")
}}}
where the `<charfield>` had **`choices` containing //bytestring// db
values and //unicode// string labels** (i.e. `choices=[(<bytes>,
<str>),...]`)
I reproduced this in isolation using a modified version of
[https://docs.djangoproject.com/en/3.0/ref/models/fields/#choices the
Students example from the docs]:
{{{
#!python
class Student(models.Model):
name = models.CharField(max_length=300)
FRESHMAN = 'FR'
SOPHOMORE = 'SO'
JUNIOR = 'JR'
SENIOR = 'SR'
GRADUATE = 'GR'
YEAR_IN_SCHOOL_CHOICES = [
(FRESHMAN, u'Freshman'),
(SOPHOMORE, u'Sophomore'),
(JUNIOR, u'Junior'),
(SENIOR, u'Senior'),
(GRADUATE, u'Graduate'),
]
year_in_school = models.CharField(
max_length=2,
choices=YEAR_IN_SCHOOL_CHOICES,
default=FRESHMAN,
)
}}}
The main modification is that the `choices` labels are explicitly unicode,
but the db values are unprefixed strings (bytestrings in Python 2, unicode
in Python 3). (Note that the actual code generated choices from an `Enum`,
which when combined with Python 2 using unicode literals causes bytestring
db values and unicode labels used above.)
In practice, I wasn't able to reproduce the error without splitting up the
`year_in_school` migration from the model creation. (The `name` field was
added to the model to create an initial migration.)
Running the `year_in_school` migration using Django 1.11.28 (on Python
2.7) generates the following migration:
{{{
#!python
# -*- coding: utf-8 -*-
# Generated by Django 1.11.28 on 2020-02-07 17:07
from __future__ import unicode_literals
from django.db import migrations, models
class Migration(migrations.Migration):
dependencies = [
('djangodebug', '0001_initial'),
]
operations = [
migrations.AddField(
model_name='student',
name='year_in_school',
field=models.CharField(choices=[(b'FR', 'Freshman'), (b'SO',
'Sophomore'), (b'JR', 'Junior'), (b'SR', 'Senior'), (b'GR', 'Graduate')],
default=b'FR', max_length=2),
),
]
}}}
**Running that migration in Django 1.11 (on either Python 2 or 3) works
fine. Running the migration in Django 2.2 throws the following error**:
{{{
django.db.utils.OperationalError: (1067, "Invalid default value for
'year_in_school'")
}}}
= Additional Notes =
== Workarounds ==
- Downgrade to Django 1.11 and run migrations, then revert to Django 2.2
- Manually modify migration files to use unicode strings (i.e. remove `b`
prefix from strings)
--
Ticket URL: <https://code.djangoproject.com/ticket/31245>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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