HiddenField is not called for patch verb

[abtinmo]

class ClubValidateSerializer(serializers.ModelSerializer):
    user = serializers.HiddenField(default=serializers.CurrentUserDefault())

  class Meta:
      model = Club
      fields = ('id', 'validated', 'user')
      read_only_fields = ('id',)

  def update(self, instance, validated_data):
      if instance.validated == validated_data['validated']:
          return instance
      history = ClubValidateHistory(club=instance, validator=validated_data['user'],
                                    from_state=instance.validated, to_state=validated_data['validated'])
      instance.validated = validated_data['validated']
      instance.save()
      history.save()
      return instance

Expected behavior

I want to get the user field in validated_data, but it throws KeyError. It from a patch update.
Actual behavior

history = ClubValidateHistory(club=instance, validator=validated_data['user'],
KeyError: 'user'
"PATCH /backend/clubs/4/validate/ HTTP/1.1" 500 17633

link to original issue #6560

[denisSurkov]

I have the same issue:

The problem

Docs state:

HiddenField

...
For example, to include a field that always provides the current time as part of the serializer validated data, you would use the following:

But HiddenField is skipped during validation if serializer has partial=True. So HiddenField does not always provide default value.

How to reproduce

from rest_framework import serializers


class DemoCallable:
    def __call__(self, *args, **kwargs):
        return 'does not matter'


class DemoSerializerWithHiddenField(serializers.Serializer):
    some_field = serializers.CharField()
    demo_hidden = serializers.HiddenField(default=DemoCallable())

    def validate(self, attrs):
        print(attrs)
        return attrs


partial_serializer = DemoSerializerWithHiddenField(data={
    "some_field": "hidden ignored"
}, partial=True)
partial_serializer.is_valid(raise_exception=True)

print(partial_serializer.validated_data)
# OrderedDict([('some_field', 'hidden ignored')])
# OrderedDict([('some_field', 'hidden ignored')])


serializer = DemoSerializerWithHiddenField(data={
    "some_field": "hidden not ignored"
}, partial=False)
serializer.is_valid(raise_exception=True)

print(serializer.validated_data)
# OrderedDict([('some_field', 'hidden not ignored'), ('demo_hidden', 'does not matter')])
# OrderedDict([('some_field', 'hidden not ignored'), ('demo_hidden', 'does not matter')])

Possible solution

from rest_framework import serializers

class HiddenField(serializers.HiddenField):
    def validate_empty_values(self, data):
        return (True, self.get_default())

    def get_default(self):
        return self.default(self)


class DemoCallable:
    def __call__(self, *args, **kwargs):
        return 'does not matter'


class DemoSerializerWithCustomHiddenField(serializers.Serializer):
    some_field = serializers.CharField()
    demo_hidden = HiddenField(default=DemoCallable())

    def validate(self, attrs):
        print(attrs)
        return attrs

partial_serializer = DemoSerializerWithCustomHiddenField(data={
    "some_field": "custom hidden not ignored"
}, partial=True)
partial_serializer.is_valid(raise_exception=True)

print(partial_serializer.validated_data)
# OrderedDict([('some_field', 'hidden not ignored'), ('demo_hidden', 'does not matter')])
# OrderedDict([('some_field', 'hidden not ignored'), ('demo_hidden', 'does not matter')])


serializer = DemoSerializerWithCustomHiddenField(data={
    "some_field": "custom hidden not ignored also"
}, partial=False)
serializer.is_valid(raise_exception=True)

print(serializer.validated_data)
# OrderedDict([('some_field', 'custom hidden not ignored also'), ('demo_hidden', 'does not matter')])
# OrderedDict([('some_field', 'custom hidden not ignored also'), ('demo_hidden', 'does not matter')])

Caveats

I think it's irresponsible to ignore overriding solution HiddenField breaks partial behavior, bacause partial has to return only provided subset.

I see two options:

• Mention that HiddenField does not appear on partial (aka PATCH) and don't touch HiddenField implementation;
• Fix HiddenField but change version. I don't like the idea changing major version, but i don't know how to do it other way.

[denisSurkov]

@auvipy , can I add this "Caution" notice, then we would continue discussing is this behavior okey or not?

I'll make PR

[auvipy]

yes please

[auvipy]

I will check the code that time as well

[denisSurkov]

@auvipy , are there any updates?

[auvipy]

I'm bit busy with other priorities right now.