SwitchTransition children may be equal if both keys are null #526
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Add test for null key
If this was called with a key of the Router's location.key and this is null then the children were not equal and the transition was repeatedly fading in and out. This could be seen by opening a new window and browsing to a site where the user had a valid token.
Fix broken build, {null} not null
taion
reviewed
Jul 25, 2019
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If they have literally no key, then I don't see how we can say one thing or another. In this kind of case, why couldn't you just take e.g. "@@unknown" or something as a fallback key and be more explicit in application space, as opposed to forcing the library into potentially-surprising behavior?
| React.isValidElement(newChildren) && | ||
| oldChildren.key != null && | ||
| oldChildren.key === newChildren.key | ||
| ((oldChildren.key == null && newChildren.key == null) || oldChildren.key === newChildren.key) |
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Why would we want to treat null and undefined the same here?
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@taion, OK. This is how I initially coded it but decided it would be better handled in the component. I'll close the fork therefore.
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If the SwitchTransition's children both have a null key then they were not equal. If the Router's location has no key then the children were being continually re-rendered with the animation applied.