Fix #34 -- Support migrations for blank fields

pictures/models.py

@@ -76,13 +76,13 @@ def delete(self):
 class PictureFieldFile(ImageFieldFile):
     def save(self, name, content, save=True):
         super().save(name, content, save)
-        if self:
-            self.save_all()
+        self.save_all()
 
     def save_all(self):
-        from . import tasks
+        if self:
+            from . import tasks
 
-        tasks.process_picture(self)
+            tasks.process_picture(self)
 
     def delete(self, save=True):
         self.delete_all()

tests/test_migrations.py

@@ -185,6 +185,28 @@ class Meta:
         )
         assert path.exists()
 
+    @pytest.mark.django_db
+    def test_to_picture_field_blank(self, request, stub_worker):
+        class FromModel(models.Model):
+            picture = models.ImageField(blank=True)
+
+            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/", blank=True)
+
+            class Meta:
+                app_label = request.node.name
+                db_table = "testapp_profile"
+
+        ToModel.objects.create(name="Luke")
+        stub_worker.join()
+        migration = migrations.AlterPictureField("profile", "picture", PictureField())
+        migration.to_picture_field(FromModel, Profile)
+
     @pytest.mark.django_db
     def test_to_picture_field__from_stdimage(
         self, request, stub_worker, image_upload_file