Dispose reaction on error inside rendering

[andykog]

@mweststrate, sometimes in complex apps, when error happens inside rendering, we can't see original error, because of additional forceUpdate.
I've spent an hour trying to isolate this user-case: https://jsfiddle.net/Sl1v3r/1adco8hx/
May be you have a better idea on how to fix this?

[mweststrate]

Updated the fiddle with a build based on this PR: https://jsfiddle.net/1adco8hx/4/

Can you elaborate why this PR makes a difference? Is that because how React handles errors internally? If that is the case I think this approach is fine.

Maybe a safety check if dispose isn't undefined, although I think theoretically that cannot be the case.

[andykog]

@mweststrate, I'm not completely sure, but I think, the problem is that when exception occurs inside render, react have no problem with handling it, but if there is synchronous forceUpdate after that, react throws it's own exception in some cases (Cannot read property 'getHostNode' of null). I can try to investigate, maybe that can & should be fixed inside React.

[mweststrate]

@andykog would you be able to add tests that make the difference clear? I think this is a good addition, but might be nice to see the exact difference

[andykog]

@mweststrate, I've found that there is definitely nothing wrong with mobx-react, sometimes react just throws own exception when you call forceUpdate on component that met error during rendering. Here is an example without mobx: https://jsfiddle.net/Sl1v3r/70rd04yp/

So I've simply checked that components stop updating after error: 48319cc

(Maybe I'l make an issue/pr in react, if I'll manage to understand the root cause.)

[mweststrate]

Merged into v4 branch