Unhandled rejection in Firefox 69

[chasenlehara]

Firefox 69 now emits the unhandledrejection event by default. Unfortunately, there’s a bug where the unhandled rejection event is emitted when source.start() rejects from new ReadableStream(source). This bug affects this test:

can-ndjson-stream/can-ndjson-stream-test.js

Lines 89 to 116 in abbffd2

	conditionalAsyncTest('malformed json', function(assert) {
	var malformed_string = "{\"1\":2}\n{sss: 2}";
	var readObjects = [];
	var todoStream = ndjsonStream( readableStreamFromString(malformed_string) );
	var reader = todoStream.getReader();
	var errorCaught = false;
	function errCheck() {
	errorCaught = true;
	}
	var done = assert.async();
	var allDone = reader.read().then(function read(result) {
	if (result.start) {
	return;
	}
	readObjects.push(result.value);
	return reader.read().then(read, errCheck);
	}, errCheck);
	allDone.then(function(){
	assert.strictEqual(errorCaught, true, "malformed json string should cause an error");
	done();
	}, function(){
	assert.strictEqual(errorCaught, true, "rejected: malformed json string should cause an error");
	done();
	});
	});

I don’t think we can do anything about this, so for the purposes of testing, I think we should work around it by adding QUnit.onUnhandledRejection = function() {} to our test so the unhandled rejection is “handled” and the tests don’t fail in Firefox 69.

The alternative is to change the main CanJS test suite to run Firefox 68 until this bug gets fixed, but I think that’s a worse alternative because I don’t think we should test against an older version of Firefox just because of this issue.