Support Inertia 2.0 deferred props feature

[mrfolksy]

NOTE: I couldn't find much documentation on the mechanics for this feature, so I worked from the inertia-laravel package as well as the inertia client package to figure out what was going on. I'm not very familiar with php or Laravel, but testing with unit tests and a small local app indicates this works.

Details

As of version 2.0, Inertia supports the ability to defer the fetching of props until after the page has been initially rendered. Essentially this is similar to the concept of Lazy props however Inertia provides convenient frontend components to automatically fetch the deferred props after the page has initially loaded, instead of requiring the user to initiate a reload. For more info see Deferred props in the Inertia documentation.

This PR introduces a defer function to mark props to be deferred, examples below

from inertia import defer, inertia

@inertia('ExampleComponent')
def example(request):
  return {
    'name': lambda: 'Brandon', # this will be rendered on the first load as usual
    'data': defer(lambda: some_long_calculation()), # this will only be run after the frontend has initially loaded and inertia requests this prop
  }

Grouping requests

By default, all deferred props get fetched in one request after the initial page is rendered, but you can choose to fetch data in parallel by grouping props together.

from inertia import defer, inertia

@inertia('ExampleComponent')
def example(request):
  return {
    'name': lambda: 'Brandon', # this will be rendered on the first load as usual
    'data': defer(lambda: some_long_calculation()),
    'data1': defer(lambda: some_long_calculation1(), 'group'), 
    'data2': defer(lambda: some_long_calculation1(), 'group'),
  }

In the example above, the data1, and data2 props will be fetched in one request, while the data prop will be fetched in a separate request in parallel. Group names are arbitrary strings and can be anything you choose.

[BrandonShar]

Thank you @mrfolksy this looks great! I just have a couple minor changes I'd like before we merge, but the structure looks perfect.

[BrandonShar]

this is almost too clever, it took me a few reads 😄 I like it though!

[BrandonShar]

looks like some formatting got messed up in this file

[mrfolksy]

Thanks for spotting this, I realised whilst making this change that my default formatting tools were messing things up, so switched the off. Missed this file!

I've noticed a mix of indentation levels across the project, either 2 or 4 spaces. The below are examples from http.py.

# indentation = 2 spaces
def partial_keys():
  return request.headers.get('X-Inertia-Partial-Data', '').split(',')

# indentation = 4 spaces
def location(location):
    return HttpResponse('', status=HTTPStatus.CONFLICT, headers={
      'X-Inertia-Location': location,
    })

The project may want to consider adding a formatting tool such as black or ruff at some point. If you are open to this I could raise a PR....

[BrandonShar]

The laravel and rails versions use a default group of "default", could we add that here?

[BrandonShar]

super small thing, could we add a named key to the example?

'data1': defer(lambda: some_long_calculation1(), group='group')

[mrfolksy]

Thank you @mrfolksy this looks great! I just have a couple minor changes I'd like before we merge, but the structure looks perfect.

Thanks for the feedback @BrandonShar, appreciate it, I’ll make the amendments over the next few days.

[mrfolksy]

@BrandonShar, changes have been made, let me know if there are any other changes needed.

[BrandonShar]

Thanks @mrfolksy ! I just corrected conflicts so if you could take a quick look and make sure my commit looks right we'll be good to merge!

Also, some type of formatting tool would be awesome here. If you have one you've had success with, I'd be happy to merge it!

[BrandonShar]

I went ahead and merged it because I'm working on some things right now and I didn't want to conflict again 😄