Merge returns a new object even when there is no change about seamless-immutable

[rtfeldman]

Thanks for bringing this up!

Unfortunately, there would be a significant performance cost to enabling this; merge would have to keep track of whether any modifications had been made, and inspect every current value before merging along the way.

I don't think the performance overhead is worth making this work.

[tusharmath]

This is a little wierd because u see —

var obj = Immutable({
  a: {aa: 1},
  b: {bb: 2}
})
var obj2 = obj.merge({b: {bb: 2}}, {deep: true})

console.log(obj.b === obj2.b, obj.a === obj2.a) // actually returns true for both cases.

So you are doing a check here right? I can get the same behavior by just wrapping the whole object inside another temp object.

[rtfeldman]

Hm, sure enough! It looks like we're already doing this and incurring the performance cost, so I guess it's empirically not a performance problem. 😆 My bad!

I'll look into this.

[rtfeldman]

Fixed and published as 4.0.2. Thanks for reporting this @tusharmath, and sorry I didn't look far enough into it the first time around!

[tusharmath]

@rtfeldman No need for sorry. Thanks a ton for fixing it so quickly.

[zuk]

Looks like this is still happening for objects with nested arrays. For example:

var a = Immutable({foo: []})
var b = Immutable({foo: []})
var ab = a.merge(b, {deep: true})
ab === a  // => false

Without a nested array it works as expected:

var a = Immutable({foo: {}})
var b = Immutable({foo: {}})
var ab = a.merge(b, {deep: true})
ab === a  // => true

[rtfeldman]

@zuk can you open a separate issue for that?

[zuk]

Sure, opened it as #94