Add option to exclude function properties when encoding objects

[brentd]

The behavior of JSON.stringify is to exclude properties on an object that store a function:

JSON.stringify({ f: function(){} }) // '{}'

Current behavior of msgpack-lite:

msgpack.decode(msgpack.encode({ f: function(){} })) // { f: null }

Behavior this PR introduces - excluding functions is the new default:

var obj = { f: function(){} }

msgpack.decode(msgpack.encode(obj)) // {}

// To get the old behavior
var codec = msgpack.createCodec({functions: true})
msgpack.decode(msgpack.encode(obj, {codec: codec})) // { f: null }

Justification

The behavior of JSON is convenient for me, because when prototyping ideas, I often serialize whole ES6 class instances without explicitly picking properties (I'm lazy). msgpack-lite already excludes the class prototype's functions since it uses Object.keys to encode objects, but functions set as properties on the object (like functions that are bound using the common idiom in the constructor) will remain.

class Foo {
  constructor() {
    this.someProp = 123
    this.boundFunc = this.boundFunc.bind(this)
  }

  someFunc() {
    return "hello"
  }

  boundFunc() {
    return this
  }
}

msgpack.decode(msgpack.encode(new Foo())) // { someProp: 123, boundFunc: null }

boundFunc would be sent over the wire as null and is of no benefit.

That said, I realize someone out there might have actually added a custom encoder for functions, so excluding them by default is maybe not the right solution. 100% open to discussing and making any adjustments necessary.

An alternative idea may be a codec option which allows you to exclude certain types from serialization.

[brentd]

Closing since there doesn't seem to be any interest.

[kawanet]

I'm sorry to the late response. I was pretty busy for those months.
I'm currently working for Issue #76. I don't think it will take a long time to wait until merging.
I'd like to merge the PR #78 at the same time with merging the similar issue #71 .

Issue #71 wants to map undefined to be stripped.

PR #78 wants to map function to null.

Those two seem similar requests. Your code looks pretty clean. LGTM. The option parameter name functions may give confused, however, at the contrast of yet another option made with issue #71 . Could I ask you a pair of option parameter names of those two?

• ignore_function
• function_null
• function_to_null
• strip_undef
• ignore_undef
• etc

I like the new default behavior given with your patch.

var obj = { f: function(){} }
msgpack.decode(msgpack.encode(obj)) // {}

Idea:

• ignore_function is true per default which removes the property. If it is false, it runs as before.
• ignore_undef is true/false per default which removes/keeps the property.

I'm more happy when you could also give a code and README for those two!

[brentd]

Sorry @kawanet, I hope I didn't make you feel guilty - I know how it goes. I was just cleaning out my PR queue.

Thanks very much for the feedback. I'll do what I can to address your comments.