Add 'default' value in OPTIONS

[cyberj]

For some frameworks who rely on automatic form generation (Angular, Polymer..) we need to see the default option provided in OPTIONS metadata.

I saw your concerns on Model's default attribute in #2683 so I have not included this on ModelSerializer for now.

But I think DRF shoul'd pass the model's default attribute in the rest_framework.field.Field when using a ModelSerializer to let thoses frameworks know what will be the value if not provided.

[xordoquy]

Hi, thanks for the PR.
Is it possible to include a test with a CurrentUserDefault to make sure your change won't break this sort of default ?

[Ernest0x]

@cyberj I had the same need so I created pull request #3750. I think the 'initial' field is exactly what frontends should take into account for form building. The 'default' field is for setting a value in the backend side if no input has been given.

[cyberj]

@Ernest0x So i case of a ModelSerializer we have to manually provide an initial attribute for each Fields? I can understand the logic, and Django use the same with forms, but it can save time to grab the Model's default to populate the initial attribute.

[cyberj]

Yeah it make more sense to use the initial attribute in metadatas.
Implementing something to pass the default attribute from models to Serializer's initial is more a design decision.

[Ernest0x]

@cyberj Yes, If we also want to base the initial attribute of a ModelSerializer field to the default attribute of the corresponding model field, that is another decision to be taken. As an inspiration, as stated in the official documentation, Django's ModelForm (the equivalent of a ModelSerializer) uses in some cases the default value of a model field as an initial selection:

If the model field has choices set, then the form field’s widget will be set to Select, with choices coming from the model field’s choices. The choices will normally include the blank choice which is selected by default. If the field is required, this forces the user to make a selection. The blank choice will not be included if the model field has blank=False and an explicit default value (the default value will be initially selected instead).

[xordoquy]

@cyberj @Ernest0x thanks for sharing your thoughts, this will help taking a decision on that topic.

[tomchristie]

I'm not in favor of us making any changes to how we handle OPTIONS requests right now, at least until there's eg. some structured content type or schema that we're working against.

Custom requirements should implement this as a custom metadata class. For bonus points package it up and we can reference it from the docs.

http://www.django-rest-framework.org/api-guide/metadata/