Add setter for the ID_ATTRIBUTE_NAME to top-level React

[dvdplm]

To facilitate use-cases where multiple React apps are running on the same page,
expose the DOMPropery ID_ATTRIBUTE_NAME on the top-level React object and make
ReactMount reference the propery from DOMPropery rather than its own local copy.

This is most probably not the right place to add something like this, so feedback
with suggestions is most welcome.

This is based off master (currently 0.14-beta3). Issue with background: #1939

[sebmarkbage]

The biggest problem when this happens is when you have two different Reacts that are unaware of each other. I.e. two different npm packages. Perhaps even of the same package and maybe even same version. It seems difficult for these two coordinate the ID even if they could set it manually.

It'd be better if we could auto-gen this ID so that it is unique. However, if a tree is server rendered, these IDs are already in use so that pattern have to be picked up potentially.

Another solution is something like we added in 0.14 where we look up the root ID to see if it belongs to this React and otherwise ignores it.

[sophiebits]

#1939 is closed so we shouldn't need this any more. If more issues pop up we can address them separately.

[hakunin]

Right now it seems impossible to change ID_ATTRIBUTE_NAME, many say they had to fork the repo.
It might be due to the other file caching the value of ID_ATTRIBUTE_NAME so that when its changed, it still looks for the old one (which is fixed with this PR).

I think this should be reopened and fixed on v14.

[gaearon]

Is there any particular problem that prevents you migrating to 15? We’ve been delaying 15 for a while now and really want to get it out. RC2 should be solid enough for you to try adopting.

Spending more effort on 14 branch right now is possible but will negatively affect development of 15.x, especially as it may introduce more issues which are not even relevant to 15 anymore. What do you think?

[hakunin]

I upgraded to v15 and also tried this fix and unfortunately the fix didn't work in my case (collision with Grammarly) so I am all for releasing v15.

[gaearon]

👍 Stay tuned, it’s coming soon!