validate_is_mapping when UpdateOne criteria is a list

[lucassimon]

Hello, I am trying to update a document but I got this error. Follow above the command.

self._collection.update_one(
                {"taxId": tax_id, "someField": {"$ne": product.lower()}},
                [
                    {
                        "$set": {
                            "someField": {
                                "$ifNull": [
                                    {"$concatArrays": ["$someField", [product.lower()]]},
                                    [product.lower()],
                                ],
                            },
                        }
                    },
                ],
            )

So, when I run this command. I got this exception on mongomock/collections.py

TypeError: update must be an instance of dict, bson.son.SON, or other type that inherits from collections.Mapping

venv/lib/python3.11/site-packages/mongomock/collection.py:79: TypeError

This function validates the option for update

ipdb> Mapping
<class 'collections.abc.Mapping'>
ipdb> option
'update'
ipdb> value
[{'$set': {'someField': {'$ifNull': [{'$concatArrays': ['$someField', ['foo']]}, ['foo']]}}}]
ipdb> isinstance(value, Mapping)
False

So, i don't know if it is a bug, because when I ran this command in a mongosh its successfully.

{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

How can I do this update correctly, using mongomock and updating the someField field correctly?

• When the field does not exist someField, it creates a field as an array with value 'foo'.
• When the field is an array. Append the foo value.
• When the field is someField:null, change/replace the field as array with value someField:['foo']

And how can I fixes this "bug" to accept my update criteria [{'$set': {'someField': {'$ifNull': [{'$concatArrays': ['$someField', ['foo']]}, ['foo']]}}}]. As you can see I use a list [{$set}...]