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Eliminate a frameback navigation initialization race #518

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Aug 10, 2016
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Eliminate a frameback navigation initialization race #518

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9 changes: 6 additions & 3 deletions packages/react-server/core/FramebackController.js
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Original file line number Diff line number Diff line change
Expand Up @@ -289,12 +289,15 @@ class FramebackController extends EventEmitter {
// If the frame has a client controller we'll listen to when
// _it_ tells us it's done loading.
//
if (clientController && !clientController.__parentIsListening) {
clientController.__parentIsListening = true;
clientController.context.onLoadComplete(this._handleFrameLoad.bind(this, frame));
}

// It may have finished _before_ we get here, so we'll also check
// whether it has already set its `_previouslyRendered` flag.
//
if (clientController && !clientController.__parentIsListening && !clientController._previouslyRendered) {
clientController.__parentIsListening = true;
clientController.context.onLoadComplete(this._handleFrameLoad.bind(this, frame));
if (clientController && !clientController._previouslyRendered) {
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Can this be an else if block? or even an else block? clientController.__parentIsListening is set on the first load, as is clientController._previouslyRendered -- are the two separate checks because there's asynchrony and users may perform navigations before we've finished loading?

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Can this be an else if block? or even an else block?

It can't, actually. You'll notice that previously the bodies of the two cases were together, and the conditionals were anded. In the case where the frame's load event fires before the client controller finishes rendering we still need both to happen.

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Basically: We always need to wire up our listener (once). And, in the case where the event we're listening to hasn't fired yet, we'll bail out early and wait for it.

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there's asynchrony and users may perform navigations before we've finished loading?

It's actually just a race between the browser's load event and the client controller finishing its render. No user interaction needed.

return;
}

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