How the Object Key Filter work

[ext-singlad]

Hi,

We have been using this library and incredibly happy with the results, saves our lot of time in Json transformations.

We have a scenario where it is required not to omit the keys where value is null or empty string.
I found that this can be achieved as explained here -
https://github.com/schibsted/jslt/blob/master/docs/api.md#object-key-filter

Now in the given syntax if I replace the filter with ". == null or . == {} or . == []" I don't get the desired result, I am getting emply json in the output, when I pass true, I get the expected results. Can you please help me with the correct way how to pass the `. == null or . == {} or . == []' in the filter?

Expression e = new Parser(reader)
  .withObjectFilter(". == null or . == {} or . == []")
  .compile();

JSLT:

{
        "commodity": {
            "en": .COMMODITY_NAME_EN,
            "zh": .COMMODITY_NAME_ZH
        }
    }

Input Json:

{
"COMMODITY_NAME_EN": "ABC",
}

Expected Output Json:

{
        "commodity": {
            "en": "ABC",
            "zh": null
        }
    }

[larsga]

By default JSLT omits some values from objects, such as null. By setting the filter you can provide a new rule for what should be omitted. Basically, JSLT omits a value when the filter returns false.

So if the filter is true then no values are omitted, since the filter always evaluates to true. You're basically turning filtering off. That sounds like what you want?

[ext-singlad]

With true it is working fine.
how about if I have to discard values fields only if the value is null(. == null) and retain all other fields with empty json({}) and array([]).

[larsga]

You want the filter to return true when the value should be omitted, right? So you want . != null. In other words: keep everything except null.

[ext-singlad]

yes that's correct.

[larsga]

That's good. Can we close this issue now?

[ext-singlad]

Sorry bit confused.
If I pass in the filter ". == null"
will it only consider null and omit others or vice versa.

[larsga]

The filter says what to keep. So if you say . == null it means you only want to keep null.

[ext-singlad]

But it is not working. if I am passing . == null getting empty json {} in the output for the shared example.

[larsga]

This is my previous comment. It explains why you get an empty JSON:

So if you say . == null it means you only want to keep null.