Merge pull request #8 from open-craft/haikuginger/add-character-lengt…

…h-migration

Adding custom key length migration

django_lti_tool_provider/migrations/0002_reduce_custom_key_length.py

@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+from django.db.models import Max
+from django.db.models.functions import Length
+
+def check_field_max_length_lteq_190(apps, schema_editor):
+    """
+    Check to see if we've got any data in the table that prevents us from
+    migrating the length of the column down to 190; if so, raise an exception.
+    """
+    LtiUserData = apps.get_model('django_lti_tool_provider', 'LtiUserData')
+    max_custom_key_length = LtiUserData.objects.aggregate(length=Max(Length('custom_key')))['length']
+    if max_custom_key_length > 190:
+        raise ValueError('Cannot perform migration: values of \'custom_key\' with length '
+                         '{} exceed the expected length 190.'.format(max_custom_key_length))
+
+
+class Migration(migrations.Migration):
+    """
+    Note that this migration is a no-op for instances created using the current
+    state of the initial migration. However, a previous version of the initial
+    migration set the maximum length of 'LtiUserData.custom_key' to 400, which is
+    longer than allowed for a MySQL 5.5 CharField. Thus, this migration is intended
+    to bring databases set up by the previous version of the initial migration
+    into parity with databases set up by the current version.
+    """
+
+    dependencies = [
+        ('django_lti_tool_provider', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            code=check_field_max_length_lteq_190
+        ),
+        migrations.RunSQL(
+            sql=migrations.RunSQL.noop,
+            state_operations=[
+                # This is a shim. Django is oh-so-efficient, so if it detects
+                # that the database should be in a state based on previous migrations,
+                # it won't perform the operations to move to that state. This tells
+                # Django "hey, I'm in this different state" without actually modifying
+                # the database. This is not a reversible operation.
+                migrations.AlterField(
+                    model_name='ltiuserdata',
+                    name='custom_key',
+                    field=models.CharField(default=b'', max_length=400)
+                )
+            ],
+        ),
+        migrations.AlterField(
+            model_name='ltiuserdata',
+            name='custom_key',
+            field=models.CharField(default=b'', max_length=190),
+        ),
+    ]

setup.py

@@ -42,7 +42,7 @@ def package_data(pkg, root_list):
 # Main ##############################################################
 setup(
     name='django_lti_tool_provider',
-    version='0.1.2',
+    version='0.1.3',
     license="GNU AFFERO GENERAL PUBLIC LICENSE",
     description='IMS LTI Tool Provider Django Applocation',
     long_description=README,