a method to serialize object.Object into a JSON compatible struct

[dsikes]

With eval.Execute returning the actual object.Object, it would be very useful to have a way to convert the object.Object into a struct that can be serialized as JSON.

A simple eval script can then be used to create JSON views by plucking the data from the object, and returning a different view of the data, like in this sample script:

if (name == "Dan") {
  return {
    "first_name": name,
   "city": address.city,
  };
}

Even though my actual object contains significantly more data, in this particular case, it'd only be a JSON object that returns a first name and a city.

[skx]

I think the general case is pretty hard, because I can imagine a script which ended:

  return 3;

That's not something you can return as json unless you changed it to:

  { "return": 3}

That said I think the hash object is a good exception. I could add a JSON interface to allow hashes, specifically, to be converted to json. So your example would work.

(I guess similarly an array-object could be made to work, providing all the members had the same type. So return [3,4,5]; or return [ "foo", "bar", "baz" ];.)

Would hash-only suffice for your use-case?

[dsikes]

Yes, hash only would work. I think that is a reasonable expectation to be fair to your point as well.
If a script returns a non hash, the caller likely wouldn't want to serialize it as JSON directly from the return of the evalfilter.

[skx]

Hrm, now I say that of course 3 is valid JSON. As is "Steve".

So I can implement for:

• Numbers.
• Strings.
• Bools.
• Hashes.
• Arrays.

That'd probably suffice for most cases.

[dsikes]

Thats true. Good point. How do you see one serializing the return object of the eval filter as JSON?

[skx]

I would probably say you'd write something like this:

 // prepare
 ret, err := eval.Run(blah)
 
 helper, ok := red.(object.ToJSON)
 if !ok {
    panic("object doesn't implement the ToJSON interface");
 }

 byte := helper.ToJSON()

At which point byte would contain the JSON. (Or it could be a string. Unsure.)

[dsikes]

That LGTM. How difficult is something like that to implement?

[skx]

I don't think it would take too long - I'd just need to define the interface and then add the ToJSON method to each object-type beneath objects/.

Handling the case of recursion / hashes will be harder than the string/bool/integers, but even so I think a couple of hours should suffice.

I'll have a stab at it tomorrow/Monday.

[dsikes]

I accidentally clicked the wrong emoji.. haha -- sounds good. Thanks for your effort.

[skx]

PR in-progress:

• Renamed the interface to JSONAble.
• Return value of JSON is (string, error).
• Used/Demonstrated in cmd/evalfilter/run_cmd.go

TODO

• Add tests.
• Handle escaping characters. e.g. If a string contains " we'd generate bogus JSON right now.

Will come back to it later in the day.

[skx]

• Test-cases added.
• Quote-handling is good, I think.

Needs more testing/experimentation, but I think it is complete now.

[dsikes]

I'll pull it in and give it a shot. Thanks for knocking it out.