Search NULL values on all field types

[michael-mri]

No description provided.

[michael-mri]

Few things to note:

• new setting NULL_VALUE which is the default null value. NULL_CHOICE_VALUE defaults to it.
• haven't yet implemented tests for each type of field
• haven't yet updated the documentation
• we may want to add null value in forms some way (especially for ModelChoiceFilter), although I am not sure how....

I struggled a bit on making form validation work: see filterset.py, lines 222-227.

Comments and suggestions are welcome :)

[rpkilby]

I can provide more details, but I'm kind of -1 on these changes since it will play poorly with non-text inputs. My recommendation is to use a separate filter to handle null values explicitly, as demonstrated in the docs.

An example of poor form usage would be number inputs. The html number input does not allow text entry, so it's not possible to submit the 'null' string. If you manually coerce the querystring to filter by the null string, then the form field will have to be altered to a text input. When re-rendering the form, the number controls will not be present. This also applies to date, datetime, and custom fields (such as any MultiValueFields).

[michael-mri]

Indeed I agree they play poorly when it comes to use them in inputs, especially those generated automatically on DRF web interface for example.
However this make REST interface more friendly, being able to filter for example author=1, author=2 or author=null the same way.

I think this also makes sense for choices filters (ChoiceFilter, ModelChoiceFilter, MultipleChoiceFilter and ModelMultipleChoiceFilter) because these are rendered using input like selectboxes where we can define what null value is.

Maybe null_value should be restricted to those filters ?

[rpkilby]

I think this also makes sense for choices filters (ChoiceFilter, ModelChoiceFilter, MultipleChoiceFilter and ModelMultipleChoiceFilter) because these are rendered using input like selectboxes where we can define what null value is.

Setting NULL_CHOICE_LABEL to a non-None value should enable null value filtering for both ChoiceFilter and ModelChoiceFilter.

If I recall correctly, null-choice filtering was not added to MultipleChoiceFilter since it would be generally non-sensical. eg, I want to filter all blogs that have no entries and that have this specific entry. You would end up with a contradictory query.

[carltongibson]

all blogs that have no entries OR that have this specific entry would make sense though right?

[rpkilby]

all blogs that have no entries OR that have this specific entry would make sense though right?

True, and it would not be much effort to extend the existing functionality it to MultipleChoiceFilter and ModelMultipleChoiceFilter.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (develop@38df0c3). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff             @@
##             develop     #639   +/-   ##
==========================================
  Coverage           ?   97.81%           
==========================================
  Files              ?       15           
  Lines              ?     1096           
  Branches           ?        0           
==========================================
  Hits               ?     1072           
  Misses             ?       24           
  Partials           ?        0

Impacted Files	Coverage Δ
django_filters/conf.py	97.22% <ø> (ø)
django_filters/filterset.py	100% <ø> (ø)
django_filters/filters.py	98.56% <100%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 38df0c3...58e70ba. Read the comment docs.

[carltongibson]

I need to make a little time to review fully but in general I quite like this. (I like the idea and the implementation looks pretty light at first glance.)

I think we probably need to review the usage docs here. (There's already a good section on filtering for null values, it probably just needs expanding.)

Also, if you rebase this is Codecov happier? (There should be a base coverage report on develop now.)

[carltongibson]

Can you set your editor to trim trailing whitespace?