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fix: prevent callback from triggering twice when callback throws #681

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Aug 31, 2021
Merged

fix: prevent callback from triggering twice when callback throws #681

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15 changes: 15 additions & 0 deletions src/__tests__/volume/callback-error.test.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
jest.useFakeTimers('modern');

// Fixes https://github.com/streamich/memfs/issues/542
it('should throw error instead of callback', () => {
const { Volume } = require('../../volume');
const vol = new Volume();

vol.writeFile('/asdf.txt', 'asdf', 'utf8', (err) => {
if (!err) {
throw new Error('try to trigger catch');
}
});

expect(() => jest.runAllTimers()).toThrow('try to trigger catch');
});
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Since wrapAsync uses setImmediate to invoke the callback that throws an error, the error can't be caught.

The only way to catch it seemed to be by stubbing setImmediate, which the jest.useFakerTimers() at the top does. This queues all callbacks until jest.runAllTimers() is invoked, which runs the queued callbacks synchronously to catch the error being thrown.

jest.useFakerTimers() seemed to stub setImmediate for all tests in the file, so I had to put it in a separate file to only influence this specific test.

5 changes: 4 additions & 1 deletion src/volume.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -826,11 +826,14 @@ export class Volume {
private wrapAsync(method: (...args) => void, args: any[], callback: TCallback<any>) {
validateCallback(callback);
setImmediate(() => {
let result;
try {
callback(null, method.apply(this, args));
result = method.apply(this, args);
} catch (err) {
callback(err);
return;
}
callback(null, result);
});
}

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