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Remove catch from Scheduler build (#20396)
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Makes debugging errors harder.

In this case, we can use `finally` instead.
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acdlite authored Dec 7, 2020
1 parent 30dfb86 commit 18d7574
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Showing 2 changed files with 29 additions and 21 deletions.
24 changes: 14 additions & 10 deletions packages/scheduler/src/forks/SchedulerDOM.js
Original file line number Diff line number Diff line change
Expand Up @@ -519,21 +519,25 @@ const performWorkUntilDeadline = () => {
// the message event.
deadline = currentTime + yieldInterval;
const hasTimeRemaining = true;

// If a scheduler task throws, exit the current browser task so the
// error can be observed.
//
// Intentionally not using a try-catch, since that makes some debugging
// techniques harder. Instead, if `scheduledHostCallback` errors, then
// `hasMoreWork` will remain true, and we'll continue the work loop.
let hasMoreWork = true;
try {
const hasMoreWork = scheduledHostCallback(hasTimeRemaining, currentTime);
if (!hasMoreWork) {
isMessageLoopRunning = false;
scheduledHostCallback = null;
} else {
hasMoreWork = scheduledHostCallback(hasTimeRemaining, currentTime);
} finally {
if (hasMoreWork) {
// If there's more work, schedule the next message event at the end
// of the preceding one.
port.postMessage(null);
} else {
isMessageLoopRunning = false;
scheduledHostCallback = null;
}
} catch (error) {
// If a scheduler task throws, exit the current browser task so the
// error can be observed.
port.postMessage(null);
throw error;
}
} else {
isMessageLoopRunning = false;
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26 changes: 15 additions & 11 deletions packages/scheduler/src/forks/SchedulerPostTaskOnly.js
Original file line number Diff line number Diff line change
Expand Up @@ -512,21 +512,25 @@ const performWorkUntilDeadline = () => {
// the message event.
deadline = currentTime + yieldInterval;
const hasTimeRemaining = true;

// If a scheduler task throws, exit the current browser task so the
// error can be observed.
//
// Intentionally not using a try-catch, since that makes some debugging
// techniques harder. Instead, if `scheduledHostCallback` errors, then
// `hasMoreWork` will remain true, and we'll continue the work loop.
let hasMoreWork = true;
try {
const hasMoreWork = scheduledHostCallback(hasTimeRemaining, currentTime);
if (!hasMoreWork) {
hasMoreWork = scheduledHostCallback(hasTimeRemaining, currentTime);
} finally {
if (hasMoreWork) {
// If there's more work, schedule the next browser task at the end of
// the preceding one.
postTask(performWorkUntilDeadline);
} else {
isTaskLoopRunning = false;
scheduledHostCallback = null;
} else {
// If there's more work, schedule the next message event at the end
// of the preceding one.
postTask(performWorkUntilDeadline);
}
} catch (error) {
// If a scheduler task throws, exit the current browser task so the
// error can be observed.
postTask(performWorkUntilDeadline);
throw error;
}
} else {
isTaskLoopRunning = false;
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