Summary:
@public
... and it's as efficient as it was before.
The previous version of the algorithm used `sourceNode` reference to know the previous state of the node to call the algorithm recursively.
That wasn't so good because of several reasons:
- It was fragile because we had two different sources of the truth of the "previous state of the tree": committed tree and source node pointer;
- We had to store weak pointers to source nodes inside cloned nodes. That is not free in terms of performance;
- The old approach introduced a constraint that all previously used and now reinserted nodes must be cloned to update source node (otherwise, the algorithm would regenerate instructions recreating already existing subtrees);
- That cloning required access to `isSealed` flag which is supposed to be a debug-only thing (that actually affects performance and must be compile-out for release builds).
The new approach compares nodes with same react tag and naturally cloning-artifacts resilient.
Yes, the new approach uses a map of inserted nodes, but the previous one already had it (otherwise there is no way to tell which nodes should be "deleted"). And anyway, this is a very little map that exists for a very little period of time.
Reviewed By: mdvacca
Differential Revision: D8709953
fbshipit-source-id: 027abb326cf45f00f7bb0bbd7c4e612578268c66
e8ec1cb16a