fix: don't share default values in ArchiveField

Passing an object as the default value to `ArchiveField` (such as `{}`)
means that we always return the same reference to multiple objects. So they're shared.
(thanks @scott-codecov for pointing that out)

So instead we will pass a class and call the class, creating a new object if we have to use it.
Noticed I hacked it a little for the default of the defaults to return `None`.
We can do the same if we ever need more complex values, or just create a new class.

I also moved the log of dbfield and archive_field None to be DEBUG and not INFO.
We are getting that quite a lot and it's making support's work hard.

database/models/core.py

@@ -238,7 +238,7 @@ def should_write_to_storage(self) -> bool:
     _report_json_storage_path = Column("report_storage_path", types.Text, nullable=True)
     report_json = ArchiveField(
         should_write_to_storage_fn=should_write_to_storage,
-        default_value={},
+        default_value_class=dict,
     )
 
 
@@ -358,7 +358,7 @@ def should_write_to_storage(self) -> bool:
     _flare = Column("flare", postgresql.JSON)
     _flare_storage_path = Column("flare_storage_path", types.Text, nullable=True)
     flare = ArchiveField(
-        should_write_to_storage_fn=should_write_to_storage, default_value={}
+        should_write_to_storage_fn=should_write_to_storage, default_value_class=dict
     )
 
 

database/models/reports.py

@@ -170,7 +170,7 @@ def _should_write_to_storage(self) -> bool:
     files_array = ArchiveField(
         should_write_to_storage_fn=_should_write_to_storage,
         rehydrate_fn=rehydrate_encoded_data,
-        default_value=[],
+        default_value_class=list,
     )
 
 

database/tests/unit/test_model_utils.py

@@ -36,9 +36,7 @@ def __init__(
             self._archive_field_storage_path = archive_value
             self.should_write_to_gcs = should_write_to_gcs
 
-        archive_field = ArchiveField(
-            should_write_to_storage_fn=should_write_to_storage, default_value=None
-        )
+        archive_field = ArchiveField(should_write_to_storage_fn=should_write_to_storage)
 
     class ClassWithArchiveFieldMissingMethods:
         commit: Commit

database/utils.py

@@ -68,9 +68,9 @@ def __init__(
         should_write_to_storage_fn: Callable[[object], bool],
         rehydrate_fn: Callable[[object, object], Any] = lambda self, x: x,
         json_encoder=ReportEncoder,
-        default_value=None,
+        default_value_class=lambda: None,
     ):
-        self.default_value = default_value
+        self.default_value_class = default_value_class
         self.rehydrate_fn = rehydrate_fn
         self.should_write_to_storage_fn = should_write_to_storage_fn
         self.json_encoder = json_encoder
@@ -103,14 +103,14 @@ def _get_value_from_archive(self, obj):
                     ),
                 )
         else:
-            log.info(
+            log.debug(
                 "Both db_field and archive_field are None",
                 extra=dict(
                     object_id=obj.id,
                     commit=obj.get_commitid(),
                 ),
             )
-        return self.default_value
+        return self.default_value_class()
 
     def __get__(self, obj, objtype=None):
         cached_value = getattr(obj, self.cached_value_property_name, None)