The fake event trick for rethrowing errors in DEV fires unexpected global error handlers and makes testing harder

I'm trying to make use of componentDidCatch in the React 16 beta. I already had a global window error handler which was working fine, but it unexpectedly catches errors that I would expect componentDidCatch to have handled. That is, component-local errors are being treated as window-global errors in dev builds. The problem seems to stem from `invokeGuardedCallbackDev` in `ReactErrorUtils.js`. I think that this entire `__DEV__` block of code is problematic. The stated rational is: ``` // In DEV mode, we swap out invokeGuardedCallback for a special version // that plays more nicely with the browser's DevTools. The idea is to preserve // "Pause on exceptions" behavior. Because React wraps all user-provided // functions in invokeGuardedCallback, and the production version of // invokeGuardedCallback uses a try-catch, all user exceptions are treated // like caught exceptions, and the DevTools won't pause unless the developer // takes the extra step of enabling pause on caught exceptions. This is // untintuitive, though, because even though React has caught the error, from // the developer's perspective, the error is uncaught. ``` This is misguided because it's not about pausing on exceptions, it's about "pause on _uncaught_ exceptions." However, `componentDidCatch` makes exceptions _caught_! Rather than switching on prod vs dev and using try/catch in prod and window's error handler in dev, React should always use try/catch, but rethrow if you reach the root w

Posted by brandonbloom on Aug 16, 2017, 7:28 PM

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