Core: Search filter for null values

[theofidry]

One request often made when filtering a collection by values is the case of the null value. Sadly this is a very painful case because the value retrieved on the server side is always a string and that it's no possible with the current implementation to pass an empty value.

Unfortunately I didn't find much on the subject aside from this post which suggest a "hacky" solution: defining custom values.

I tested a little bit with a StrongLoop application and the following query ?filter[where][property]=null works whatever the type of the value is.

The only problem is for string values. Indeed it becomes impossible to search for a string with the value "null".

@dunglas, @sroze what are your though on this case? Should we do as StrongLoop which has the drawback of disabling the search filter for string properties of value "null"?

[dunglas]

There is only one proper way to handle such case. Using the explicit representation of Hydra: http://www.hydra-cg.com/spec/latest/core/#h-templated-links

Currently we only support BasicRepresentation. Work on that is welcome. An other way to handle such edge cases for now is using custom filters.

[blaues0cke]

Here is a custom filter doing this: https://gist.github.com/blaues0cke/e45a56f32439d8882390

Use it like this: ?property-name-empty=true

[theofidry]

Thanks @blaues0cke, I've rolled out mine since then ;) It was more a question of merging it back to the bundle or not.

[blaues0cke]

@theofidry Yeah, just landed in this issue after some research and wanted to share our solution with the next person that ends up here. :-)

[nicholasruunu]

In the same spirit as @blaues0cke I'll share our solution inspired by range filter:
?property[null]=true/false

https://gist.github.com/nicholasruunu/db1d840bebe4dd6de3ba20ac776dcf41

[teohhanhui]

Please see #906.

On Tue, 21 Feb 2017, 23:20 Nicholas Ruunu, [e-mail] wrote:

In the same spirit as @blaues0cke https://github.com/blaues0cke I'll
share our solution inspired by range filter: ?property[null]=true/false

https://gist.github.com/nicholasruunu/db1d840bebe4dd6de3ba20ac776dcf41

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