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fix: False positive warning about MessageChannel #522

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Merged
merged 1 commit into from
Nov 4, 2019
Merged

fix: False positive warning about MessageChannel #522

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12 changes: 7 additions & 5 deletions src/flush-microtasks.js
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Original file line number Diff line number Diff line change
Expand Up @@ -21,20 +21,22 @@ try {
// we can't use regular timers because they may still be faked
// so we try MessageChannel+postMessage instead
enqueueTask = callback => {
if (didWarnAboutMessageChannel === false) {
const supportsMessageChannel = typeof MessageChannel === 'function'
if (supportsMessageChannel) {
const channel = new MessageChannel()
channel.port1.onmessage = callback
channel.port2.postMessage(undefined)
} else if (didWarnAboutMessageChannel === false) {
didWarnAboutMessageChannel = true

// eslint-disable-next-line no-console
console.error(
typeof MessageChannel !== 'undefined',
'This browser does not have a MessageChannel implementation, ' +
'so enqueuing tasks via await act(async () => ...) will fail. ' +
'Please file an issue at https://github.com/facebook/react/issues ' +
'if you encounter this warning.',
)
}
const channel = new MessageChannel()
channel.port1.onmessage = callback
channel.port2.postMessage(undefined)
}
}

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