gristlabs_grist-core/test/client/lib/Signal.ts

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import { assert } from 'chai';
import { Signal } from 'app/client/lib/Signal';
describe('Signal', function() {
it('computes new signal from other events', function() {
const started = Signal.create(null, false);
const hovered = Signal.create(null, false);
const hoverAndStarted = Signal.compute(null, on => on(started) && on(hovered));
let flag: any = 'not-called';
hoverAndStarted.listen(val => flag = val);
function start(emit: boolean, expected: boolean) {
started.emit(emit);
assert.equal(flag, expected);
flag = 'not-called';
}
function hover(emit: boolean, expected: boolean) {
hovered.emit(emit);
assert.equal(flag, expected);
flag = 'not-called';
}
start(true, false);
start(false, false);
start(true, false);
hover(true, true);
hover(false, false);
hover(true, true);
start(false, false);
});
it('works as flag', function() {
const started = Signal.create(null, false);
const hovered = Signal.create(null, false);
const andEvent = Signal.compute(null, on => on(started) && on(hovered)).distinct();
const notCalled = {};
let andCalled = notCalled;
andEvent.listen(val => andCalled = val);
function start(emit: boolean, expected: any) {
started.emit(emit);
assert.equal(andCalled, expected);
andCalled = notCalled;
}
start(true, notCalled);
start(false, notCalled);
start(true, notCalled);
function hover(emit: boolean, expected: any) {
hovered.emit(emit);
assert.equal(andCalled, expected);
andCalled = notCalled;
}
hover(true, true);
hover(false, false);
hover(true, true);
start(false, false);
});
it('supports basic compositions', function() {
const numbers = Signal.create(null, 0);
const even = numbers.filter(n => n % 2 === 0);
const odd = numbers.filter(n => n % 2 === 1);
let evenCount = 0;
let oddCount = 0;
even.listen(() => evenCount++);
odd.listen(() => oddCount++);
assert.equal(evenCount, 0);
assert.equal(oddCount, 0);
numbers.emit(2);
assert.equal(evenCount, 1);
assert.equal(oddCount, 0);
numbers.emit(3);
assert.equal(evenCount, 1);
assert.equal(oddCount, 1);
const distinct = numbers.distinct();
let distinctCount = 0;
distinct.listen(() => distinctCount++);
assert.equal(distinctCount, 0);
numbers.emit(3);
assert.equal(distinctCount, 0);
numbers.emit(3);
assert.equal(distinctCount, 0);
numbers.emit(4);
assert.equal(distinctCount, 1);
numbers.emit(4);
assert.equal(distinctCount, 1);
numbers.emit(5);
assert.equal(distinctCount, 2);
const trafficLight = Signal.create(null, false);
const onRoad = numbers.filter(n => !!trafficLight.state.get());
let onRoadCount = 0;
onRoad.listen(() => onRoadCount++);
assert.equal(onRoadCount, 0);
numbers.emit(5);
assert.equal(onRoadCount, 0);
trafficLight.emit(true);
assert.equal(onRoadCount, 0);
numbers.emit(6);
assert.equal(onRoadCount, 1);
});
it('detects cycles', function() {
const first = Signal.create(null, 0);
const second = Signal.create(null, 0);
first.listen(n => second.emit(n + 1));
second.listen(n => first.emit(n + 1));
assert.throws(() => first.emit(1));
});
});