Add setting to convert FileField to CharField instead of TextField (#625)

Author: jcushman

AUTHORS.rst

@@ -42,6 +42,7 @@ Authors
 - Guillermo Eijo (`guilleijo <https://github.com/guilleijo>`_)
 - Hamish Downer
 - Hanyin Zhang
+- Jack Cushman (`jcushman <https://github.com/jcushman>`_)
 - James Muranga (`jamesmura <https://github.com/jamesmura>`_)
 - James Pulec
 - Jesse Shapiro

CHANGES.rst

@@ -4,6 +4,7 @@ Changes
 Unreleased
 ----------
 - Add simple filtering if provided a minutes argument in `clean_duplicate_history` (gh-606)
+- Add setting to convert `FileField` to `CharField` instead of `TextField` (gh-623)
 
 2.8.0 (2019-12-02)
 ------------------

docs/historical_model.rst

@@ -386,3 +386,16 @@ or the record invocation: ``app="SomeAppName"``.
     register(Opinion, app="SomeAppName")
 
 
+`FileField` as a `CharField`
+----------------------------
+
+By default a ``FileField`` in the base model becomes a ``TextField`` in the history model.
+This is a historical choice that django-simple-history preserves for backwards
+compatibility; it is more correct for a ``FileField`` to be converted to a
+``CharField`` instead. To opt into the new behavior, set the following line in your
+``settings.py`` file:
+
+.. code-block:: python
+
+    SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD = True
+

simple_history/models.py

@@ -545,7 +545,10 @@ def transform_field(field):
 
     elif isinstance(field, models.FileField):
         # Don't copy file, just path.
-        field.__class__ = models.TextField
+        if getattr(settings, "SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD", False):
+            field.__class__ = models.CharField
+        else:
+            field.__class__ = models.TextField
 
     # Historical instance shouldn't change create/update timestamps
     field.auto_now = False

simple_history/tests/models.py

@@ -192,6 +192,20 @@ class FileModel(models.Model):
     history = HistoricalRecords()
 
 
+# Set SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD
+setattr(settings, "SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD", True)
+
+
+class CharFieldFileModel(models.Model):
+    title = models.CharField(max_length=100)
+    file = models.FileField(upload_to="files")
+    history = HistoricalRecords()
+
+
+# Clear SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD
+delattr(settings, "SIMPLE_HISTORY_FILEFIELD_TO_CHARFIELD")
+
+
 class Document(models.Model):
     changed_by = models.ForeignKey(
         User, on_delete=models.CASCADE, null=True, blank=True

simple_history/tests/tests/test_models.py

@@ -42,6 +42,7 @@
     BucketDataRegisterChangedBy,
     BucketMember,
     CharFieldChangeReasonModel,
+    CharFieldFileModel,
     Choice,
     City,
     ConcreteAttr,
@@ -316,6 +317,19 @@ def test_file_field(self):
         self.assertEqual(create_record.file, "files/name")
         self.assertEqual(update_record.file, "")
 
+    def test_file_field_with_char_field_setting(self):
+        # setting means history table's file field is a CharField
+        file_field = CharFieldFileModel.history.model._meta.get_field("file")
+        self.assertIs(type(file_field), models.CharField)
+        self.assertEqual(file_field.max_length, 100)
+        # file field works the same as test_file_field()
+        model = CharFieldFileModel.objects.create(file=get_fake_file("name"))
+        self.assertEqual(model.file.name, "files/name")
+        model.file.delete()
+        update_record, create_record = model.history.all()
+        self.assertEqual(create_record.file, "files/name")
+        self.assertEqual(update_record.file, "")
+
     def test_inheritance(self):
         pizza_place = Restaurant.objects.create(name="Pizza Place", rating=3)
         pizza_place.rating = 4