From bff446c205e0c4d436a5147906397ab7534343f3 Mon Sep 17 00:00:00 2001 From: Markus Holtermann Date: Wed, 4 Mar 2015 09:36:53 +0100 Subject: [PATCH] [1.8.x] Fixed #24435 -- Prevented m2m field removal and addition in migrations when changing blank Thanks Mark Tranchant for the report and Tim Graham for the test and review. Backport of a9e29fae105d1ddd4e0ac2059cbe62b0ee348bc8 from master --- django/db/migrations/autodetector.py | 13 +++++++++++-- tests/migrations/test_autodetector.py | 14 ++++++++++++++ 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py index 16df9bfd91..33a9e9e166 100644 --- a/django/db/migrations/autodetector.py +++ b/django/db/migrations/autodetector.py @@ -848,8 +848,16 @@ class MigrationAutodetector(object): old_field_dec = self.deep_deconstruct(old_field) new_field_dec = self.deep_deconstruct(new_field) if old_field_dec != new_field_dec: - if (not isinstance(old_field, models.ManyToManyField) and - not isinstance(new_field, models.ManyToManyField)): + both_m2m = ( + isinstance(old_field, models.ManyToManyField) and + isinstance(new_field, models.ManyToManyField) + ) + neither_m2m = ( + not isinstance(old_field, models.ManyToManyField) and + not isinstance(new_field, models.ManyToManyField) + ) + if both_m2m or neither_m2m: + # Either both fields are m2m or neither is preserve_default = True if (old_field.null and not new_field.null and not new_field.has_default() and not isinstance(new_field, models.ManyToManyField)): @@ -870,6 +878,7 @@ class MigrationAutodetector(object): ) ) else: + # We cannot alter between m2m and concrete fields self._generate_removed_field(app_label, model_name, field_name) self._generate_added_field(app_label, model_name, field_name) diff --git a/tests/migrations/test_autodetector.py b/tests/migrations/test_autodetector.py index 3d822072ce..2d45dac7f8 100644 --- a/tests/migrations/test_autodetector.py +++ b/tests/migrations/test_autodetector.py @@ -127,6 +127,10 @@ class AutodetectorTests(TestCase): ("id", models.AutoField(primary_key=True)), ("publishers", models.ManyToManyField("testapp.Publisher")), ]) + author_with_m2m_blank = ModelState("testapp", "Author", [ + ("id", models.AutoField(primary_key=True)), + ("publishers", models.ManyToManyField("testapp.Publisher", blank=True)), + ]) author_with_m2m_through = ModelState("testapp", "Author", [ ("id", models.AutoField(primary_key=True)), ("publishers", models.ManyToManyField("testapp.Publisher", through="testapp.Contract")), @@ -1263,6 +1267,16 @@ class AutodetectorTests(TestCase): self.assertOperationTypes(changes, 'testapp', 0, ["AddField"]) self.assertOperationAttributes(changes, 'testapp', 0, 0, name="publishers") + def test_alter_many_to_many(self): + before = self.make_project_state([self.author_with_m2m, self.publisher]) + after = self.make_project_state([self.author_with_m2m_blank, self.publisher]) + autodetector = MigrationAutodetector(before, after) + changes = autodetector._detect_changes() + # Right number/type of migrations? + self.assertNumberMigrations(changes, 'testapp', 1) + self.assertOperationTypes(changes, 'testapp', 0, ["AlterField"]) + self.assertOperationAttributes(changes, 'testapp', 0, 0, name="publishers") + def test_create_with_through_model(self): """ Adding a m2m with a through model and the models that use it should be