Getting KeyError on partial update (PATCH) when 'tags' not included

[joeweiss]

Partials update (via PATCH request) is throwing a KeyError in _pop_tags when the 'tags' field's data is not included in the patch request.

In our situation, we patch a lot of records, and we only patch the fields that change.

Current implementation

    def _pop_tags(self, validated_data):
        to_be_tagged = {}

        for key in self.fields.keys():
            field = self.fields[key]
            if isinstance(field, TagListSerializerField):
                to_be_tagged[key] = validated_data.pop(key)

        return (to_be_tagged, validated_data)

We need the check the existence of the key before pop'ing it, correct?

    def _pop_tags(self, validated_data):
        to_be_tagged = {}

        for key in self.fields.keys():
            field = self.fields[key]
            if isinstance(field, TagListSerializerField):
                if key in validated_data:
                    to_be_tagged[key] = validated_data.pop(key)

        return (to_be_tagged, validated_data)

I'm happy to open a PR, but wanted to make sure I wasn't missing something simple or overthinking it.

[glemmaPaul]

Yeah you're absolutely right! It's strange I've never added partial=True. I'll add tests for that too. You can open a PR if you would like, thank you for bringing it up 👍

[joeweiss]

Great. I opened a PR. It needs tests though. Wasn't sure how you wanted those handled.

[joeweiss]

Hey folks. This issue is occurring again.

It looks like the fix for this issue was overwritten after the PR was accepted.

Here's where it happened:
2909a7f#diff-332a5a3794e86d0e4a5433137ec60215L48

I'm opening another PR now. Thanks!