Unhandled async errors crash Jest.

[cpojer]

On master, I changed one of the tests in jest-haste-map from toBeDefined() or something to not.toBeDefined(). It would then go on to crash Jest:

[cpojer: ~/Projects/jest (master)]$ jest "haste-map.*index"

 RUNS  packages/jest-haste-map/src/__tests__/index-test.js

/Users/cpojer/Projects/jest/packages/jest-jasmine2/node_modules/jest-matchers/build/index.js:110
        throw error;
        ^
Error: expect(received).toBeNull()

Expected value to be null, instead received
  undefined
    at HasteMap.hasteMap.once (/Users/cpojer/Projects/jest/packages/jest-haste-map/src/__tests__/index-test.js:685:62)
    at HasteMap.g (events.js:291:16)
    at emitOne (events.js:96:13)
    at HasteMap.emit (events.js:188:7)
    at Timeout.emitChange (/Users/cpojer/Projects/jest/packages/jest-haste-map/src/index.js:562:14)
    at ontimeout (timers.js:365:14)
    at tryOnTimeout (timers.js:237:5)
    at Timer.listOnTimeout (timers.js:207:5)

@DmitriiAbramov what have we done?

[cpojer]

Oh, it might have been because I didn't return the promise but instead am using Jasmine's async work. Nevertheless, we should hook up an unhandled promise handler in Jest.

[mweststrate]

Currently we use in our tests a utility to work around this in a quite cumbersome way:

/**
 * In async tests, JEST will die (in watch mode) if an exception is thrown from a callback. This utility will catch
 * the errors instead and report the test as failed in these case *
 *
 * @param {jest.DoneCallback} done
 * @param {T} callback
 * @returns {T}
 */
export function catchErrors<T extends Function>(done: jest.DoneCallback, callback: T): T {
	return function() {
		try {
			callback.apply(this, arguments)
		} catch (e) {
			done.fail(e)
		}
	} as any as T
}

which then can be used as follows:

describe("suite", () => {
	it("should handle async exceptions", (done) => {
                setTimeout(catchErrors(done, (err, res) => {
                        throw "Catched by catchErrors so that our tests properly fail!"
                        done() 
                }), 100)
        })
})

Any cleaner approach to this would be appreciated!

[mmcgahan]

this sounds somewhat similar to #1873, where done() is unreachable after failing expect calls in Promises

[julien-f]

Any news on this?

I also have a repro repo here if that can help.

[lucasconstantino]

This is some huge drawback for me :( Trying to find a way to circumvent this properly...

[theogravity]

this is quite frustrating as I have no idea where it's dying

[capaj]

@mweststrate this should be in the jest core. Seriously, this has been lying here for two months and no one opened a PR yet? 😖