Feature request: support serialisation of objects as string using json/yaml format

[t3mi]

Feature request checklist

• There are no issues that match the desired change
• The change is large enough it can't be addressed with a simple Pull Request
• If this is a bug, please file a Bug Report.

Change
Please add functions related to serialisation of objects with yaml/json formatting similar to helm ones

• toJson
• toYaml

The use case is configuration generation inside the kro's custom resource with some additional runtime values added (using to-be-implemented merge function) and store the result in the configMap.

References

• Support serialization of objects as string using json/yaml format kubernetes-sigs/kro#843

[TristonianJones]

Hi @t3mi, if you already have extension functions that do this, you're welcome to contribute them back as part of the ext/encoders.go library

[rikatz]

@t3mi just for my understanding, the idea is to get a field, convert it toYaml and parse from it, or something else?

I am asking as I am looking into a validation for something like:

data:
   something: |
       xpto: "abc"
       lorem: "ipsum"
       somearray:
       - a
       - b

I would like to do something like .data.something.toYaml().xpto == "abc" (I am not sure how costly it would be for cel-go tho).

Additionally, IIRC and if this is what you want to do, yaml is usually a subset of json, and in fact you can use the same unmarshaller from yaml to unmarshal a json: https://go.dev/play/p/2Ehij1GCAJe

So, let me know if this is what you are looking for, and @TristonianJones if this is acceptable from a cel-go side (eg.: having a .Decode() or something like that that would try to unmarshall the yaml or json inside an inline string), and I can try working on it.

[t3mi]

@TristonianJones unfortunately I don't have them

@rikatz partially yes, but have paired function as well - encode/decode. For my use case, I have an app which expects yaml configuration to operate with. This yaml configuration has some dynamic parts (if taking kro into action) like extraction of the generated api key and hostname for the third party api. Intention is to deserialise static part of the configuration into object, merge it with dynamic part and serialise it back into yaml/json string to be stored in the config map linked to the the app to work with.

[rikatz]

right, I may try something for the next few days if @TristonianJones agrees and if you are not willing to pick it :)

[rikatz]

rikatz@e39e05d

No unit test yet.

The json encoder is not working because of json strictness, it would need some fancy approach like "encode yaml/decode yaml/encode json" which may be very costly. I will think on a better approach.

Also, I am lacking unit tests here, should do it next

[gfaraj]

@rikatz any update for this?

[TristonianJones]

@t3mi are you looking for support for marshalling the object to YAML within CEL? Would it be possible for us to support the YAML conversion via ConvertToNative()? That is to say, rather than make it part of the core CEL expression language, expose it as a helper that you could call on results of the CEL evaluation?

[TristonianJones]

Most CEL objects support ConvertToNative(JSONValueType) so it's not too bad to provide an extension which consistently converts to a JSON string even if it's not a dynamic type. The other direction (string -> JSON) would always result in a dynamic type. Making this work with native objects nicely might be a bit of a challenge, but it's also doable.

[t3mi]

@t3mi are you looking for support for marshalling the object to YAML within CEL?

Yes if it's manageable and efficient. By exposing just a helper, does it mean that such encoders/decoders would need to be implemented in one or another project to support (de)serialisation?