how to handle undefined values cleanly?

[dcsan]

I'm dump ing an object, and fields without values come out like this:

fieldName: !<tag:yaml.org,2002:js/undefined> ''

how can I suppress that to either undefined or just to skip it like JSON.stringify ?

I tried some options from the safeDump

const blob = yaml.dump(obj, { skipInvalid: true, lineWidth: 200 })

https://github.com/nodeca/js-yaml#safedump-object---options-

but without success. I guess I can strip out the undefined fields, but I'd have to do a deep clean of the whole object... also check for false vs undefined etc. etc.

I tried this but it didn't have any effect:
const clean = { ...obj } // remove nulls?

Sure there must be a nicer way to handle this with js-yaml ?
Do I have to define my own schema?

related:
#456
https://stackoverflow.com/a/38340374/1146785

  async debugMessage(obj) {
    console.log('json', JSON.stringify(obj, null, 2))
    const blob = yaml.dump(obj)
    console.log('yaml', blob)
  }


// json 

{
  "msg": "router",
  "input": "sleep",
  "eventType": "action",
  "handled": {
    "handled": true,
    "doc": {
      "match": "^cont|.*",
      "goto": "prologue"
    },
    "klass": "room",
    "history": [
      "goto"
    ]
  }
}

// yaml 

msg: router
input: sleep
eventType: action
parsed: !<tag:yaml.org,2002:js/undefined> ''
handled:
  handled: true
  doc:
    match: ^cont|.*
    goto: prologue
  klass: room
  history:
    - goto

[dcsan]

bump

super annoying. currently I have to do this:

  // strip out elements with undef values for cleaner YAML dumps
  removeEmptyKeys(obj) {
    if (!obj) return {}  // fixme - handle better?
    Object.keys(obj).forEach(key => {
      // if (obj[key] && typeof obj[key] === 'object') Util.removeEmptyKeys(obj[key]);
      if (obj[key] === undefined) delete obj[key];
    });
    return obj;
  },

or the parse results default to full of junk

canTake: false
hidden: !<tag:yaml.org,2002:js/undefined> ''

[aeisenberg]

I'm having the same problem. Here's my solution, which won't work if you have a circular object or are using any special yaml types:

yaml.safeDump(JSON.parse(JSON.stringify(workflow))

[NelsonFrancisco]

An option would be a nice addition 👍

[rlidwka]

Fixed in 56d5616 (currently in dev branch).

Now undefined follows roughly the same black magic as in JSON:

• replaced with null in collections (errors out if null isn't in the schema)
• removed from mappings entirely if either key or value is undefined

If user defines custom schema for undefined, it serializes as before.

[mk-pmb]

I'd like an option what do with undefined when it's found in a mapping (dictionary), and another one for how to translate it in lists. I'd like to choose either a string as which to encode it (even the empty string in some exotic cases), or to omit it. The latter could be expressed by setting the option to false. Maybe we could also allow functions, passing them the path (array of steps) we have dived to reach the value, the current original container, and the top level original value? Then the function can dynamically decide a string or false, or throw an error.