Add support to migrate from django-stimage

pictures/migrations.py

@@ -35,7 +35,7 @@ def alter_picture_field(
         if not isinstance(from_field, PictureField) and isinstance(
             to_field, PictureField
         ):
-            self.to_picture_field(to_model)
+            self.to_picture_field(from_model, to_model)
         elif isinstance(from_field, PictureField) and not isinstance(
             to_field, PictureField
         ):
@@ -63,7 +63,15 @@ def from_picture_field(self, from_model: Type[models.Model]):
             field_file = getattr(obj, self.name)
             field_file.delete_all()
 
-    def to_picture_field(self, to_model: Type[models.Model]):
+    def to_picture_field(
+        self, from_model: Type[models.Model], to_model: Type[models.Model]
+    ):
+        from_field = from_model._meta.get_field(self.name)
+        if hasattr(from_field.attr_class, "delete_variations"):
+            # remove obsolete django-stdimage variations
+            for obj in from_model._default_manager.all().iterator():
+                field_file = getattr(obj, self.name)
+                field_file.delete_variations()
         for obj in to_model._default_manager.all().iterator():
             field_file = getattr(obj, self.name)
             field_file.save_all()

tests/test_migrations.py

@@ -3,6 +3,7 @@
 import pytest
 from django.core.management import call_command
 from django.db import models
+from django.db.models.fields.files import ImageFieldFile
 
 from pictures import migrations
 from pictures.models import PictureField
@@ -156,6 +157,51 @@ def test_from_picture_field(self, stub_worker, image_upload_file):
 
     @pytest.mark.django_db
     def test_to_picture_field(self, request, stub_worker, image_upload_file):
+        class FromModel(models.Model):
+            picture = models.ImageField()
+
+            class Meta:
+                app_label = request.node.name
+                db_table = "testapp_profile"
+
+        class ToModel(models.Model):
+            name = models.CharField(max_length=100)
+            picture = models.ImageField(upload_to="testapp/profile/")
+
+            class Meta:
+                app_label = request.node.name
+                db_table = "testapp_profile"
+
+        luke = ToModel.objects.create(name="Luke", picture=image_upload_file)
+        stub_worker.join()
+        migration = migrations.AlterPictureField("profile", "picture", PictureField())
+        migration.to_picture_field(FromModel, Profile)
+        stub_worker.join()
+        luke.refresh_from_db()
+        path = (
+            Profile.objects.get(pk=luke.pk)
+            .picture.aspect_ratios["16/9"]["WEBP"][100]
+            .path
+        )
+        assert path.exists()
+
+    @pytest.mark.django_db
+    def test_to_picture_field__from_stdimage(
+        self, request, stub_worker, image_upload_file
+    ):
+        class StdImageFieldFile(ImageFieldFile):
+            delete_variations = Mock()
+
+        class StdImageField(models.ImageField):
+            attr_class = StdImageFieldFile
+
+        class FromModel(models.Model):
+            picture = StdImageField()
+
+            class Meta:
+                app_label = request.node.name
+                db_table = "testapp_profile"
+
         class ToModel(models.Model):
             name = models.CharField(max_length=100)
             picture = models.ImageField(upload_to="testapp/profile/")
@@ -167,7 +213,7 @@ class Meta:
         luke = ToModel.objects.create(name="Luke", picture=image_upload_file)
         stub_worker.join()
         migration = migrations.AlterPictureField("profile", "picture", PictureField())
-        migration.to_picture_field(Profile)
+        migration.to_picture_field(FromModel, Profile)
         stub_worker.join()
         luke.refresh_from_db()
         path = (
@@ -176,6 +222,7 @@ class Meta:
             .path
         )
         assert path.exists()
+        assert StdImageFieldFile.delete_variations.called
 
     @pytest.mark.django_db(transaction=True)
     def test_database_backwards_forwards(self):