Using local assign in Object Semigroup

[taras]

It turns out that extend-shallow does not work as expected because it actually defaults to Object.assign when available. We need to always use our own implementation of Object.assign inside of Object Semigroup to prevent React Native from overwriting our assign with theirs.

The implementation that I added is just a little slower than Object.assign.

I can get it to be little faster than Object.assign, but I need to replace Object.keys(source).concat(Object.getOwnPropertySymbols(source)) with the following,

function allKeys(o) {
  let keys = Object.keys(o), 
      keysLength = keys.length,
      symbols = Object.getOwnPropertySymbols(o),
      symbolsLength = symbols.length,
      arr = Array(keysLength + symbolsLength),
      totalLength = keysLength + symbolsLength;

  for (let j = 0; j < keysLength; j++) {
    arr[j] = keys[j];
  }
  for (let j = keysLength; j < totalLength; j++) {
    arr[j] = symbols[totalLength - j - 1];
  }
  return arr;
}

I decided to not use it because it's pretty ugly, but we can always add it back.

[Robdel12]

Should we add a comment in here this exists because React Native does weird things?

[taras]

Yeah, good idea.

[cowboyd]

Looks good. You know a library is arriving when there are disgusting code blocks there to work around platform-specific constraints. This is actually a good thing.

Since we are only using assign here, and not elsewhere, can we just make it operate on two arguments? That should tighten the loop a little bit and then it isn't more abstract than it needs to be.

[taras]

@cowboyd done!

[cowboyd]

I think we can even make the target of {} implicit. i.e. instead of assign({}, a, b) just assign(a,b)

[cowboyd]

lol. If this were ramda, they'd probably call it append0 or _append to indicate that it's really a "bootstrap" append.