How to serialize nested object into string?

[raphael-ru]

Hi @brexhq/substation! How do I convert a nested json object into a string?

Context: I am using substation to extract the relevant keys out of a json object. To keep backwards compatability with our system I then want to turn the object into a string. I have tried using the obj.to.string, but it does not work. How do I cast this correctly?

Example

After my transforms, I have an object like this ... (Not all the keys are known beforehand.)

{"body":{"output_fields":{"evt.type":"connect","fd.lport":9125,"fd.type":"ipv6","proc.exepath":"/usr/sbin/xtables-legacy-multi","proc.pname":"kube-proxy","proc.tty":0}}}

After running some transform (like sub.tf.obj.to.string({ obj: { src: 'body', trg: 'body' } })) I want body to get serialized ...

{"body":"{\"output_fields\":{\"evt.type\":\"connect\",\"fd.lport\":9125,\"fd.type\":\"ipv6\",\"proc.exepath\":\"/usr/sbin/xtables-legacy-multi\",\"proc.pname\":\"kube-proxy\",\"proc.tty\":0}}"}

But I get the same body object as before.

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Thank you very much for making substation and all your hard work!

[shellcromancer]

Hey @raphael-ru, really good question here. Under normal circumstances, we would expect this to work with a copy transform using the gjson @tostr modifier (e.g. sub.tf.obj.cp({ obj: { src: 'body.@tostr', trg: 'body' } })), but there is a bug preventing valid JSON strings from being written as anything but objects.

We hadn't considered the use case of "string-ifying" values and have currently functionality that actively tries to write JSON objects at all possible times. I'm taking a look at how we can make this more selective. 👍

[raphael-ru]

Hi @shellcromancer! Thank you for your answer and responding so quickly! I did manage to handle it further down our pipeline, so I am not dependent on substation to implement this feature. Just thought I'd let you know that it's not urgent anymore.

[shellcromancer]

@raphael-ru As of fd858a9 on the main branch sub.tf.obj.to.string({ obj: { src: 'body', trg: 'body' } }) should work for you. Here's an example in the Substation playground CLI.