@tldraw/state/src/lib/__tests__/errors.test.ts

tldraw infinite canvas SDK (state).

import { atom } from '../Atom'
import { computed } from '../Computed'
import { EffectScheduler, react } from '../EffectScheduler'
import { haveParentsChanged } from '../helpers'
import { getGlobalEpoch, transact } from '../transactions'
import { RESET_VALUE } from '../types'

describe('reactors that error', () => {
	it('will not roll back the atom value', () => {
		const a = atom('', 1)
		react('', () => {
			if (a.get() === 2) throw new Error('test')
		})
		expect(() => a.set(2)).toThrowErrorMatchingInlineSnapshot(`"test"`)
		expect(a.get()).toBe(2)
	})
	it('will not roll back the changes in a transaction', () => {
		const a = atom('', 1)
		const b = atom('', 2)

		react('', () => {
			if (a.get() + b.get() === 4) throw new Error('test')
		})

		expect(() =>
			transact(() => {
				a.set(3)
				b.set(1)
			})
		).toThrowErrorMatchingInlineSnapshot(`"test"`)

		expect(a.get()).toBe(3)
		expect(b.get()).toBe(1)
	})
})

describe('derivations that error', () => {
	it('will cache thrown values', () => {
		let numComputations = 0
		const a = atom('', 1)
		const b = computed('', () => {
			numComputations++
			if (a.get() === 2) throw new Error('test')
			return a.get()
		})

		expect(b.get()).toBe(1)
		expect(numComputations).toBe(1)

		a.set(2)

		expect(() => b.get()).toThrowErrorMatchingInlineSnapshot(`"test"`)
		expect(numComputations).toBe(2)
		expect(() => b.get()).toThrowErrorMatchingInlineSnapshot(`"test"`)
		expect(numComputations).toBe(2)
		expect(() => b.get()).toThrowErrorMatchingInlineSnapshot(`"test"`)
		expect(numComputations).toBe(2)

		a.set(3)

		expect(b.get()).toBe(3)
		expect(b.get()).toBe(3)
	})

	it('will not trigger effects if they continue to error', () => {
		const a = atom('', 1)
		let numComputations = 0
		const b = computed('', () => {
			numComputations++
			if (a.get() % 2 === 0) throw new Error('test')
			return a.get()
		})

		let numReactions = 0
		react('', () => {
			try {
				b.get()
			} catch {
				// ignore
			}
			numReactions++
		})
		expect(numReactions).toBe(1)
		expect(numComputations).toBe(1)

		a.set(2)

		expect(numReactions).toBe(2)
		expect(numComputations).toBe(2)

		a.set(4)

		expect(numComputations).toBe(3)
		expect(numReactions).toBe(2)

		a.set(3)

		expect(numComputations).toBe(4)
		expect(numReactions).toBe(3)
	})

	it('clears the history buffer when an error is thrown', () => {
		const a = atom('', 1)
		const b = computed(
			'',
			() => {
				if (a.get() === 5) throw new Error('test')
				return a.get()
			},
			{
				historyLength: 10,
				computeDiff: (a, b) => {
					return b - a
				},
			}
		)

		expect(b.get()).toBe(1)
		const startEpoch = getGlobalEpoch()

		a.set(2)
		expect(b.get()).toBe(2)
		expect(b.getDiffSince(startEpoch)).toEqual([1])

		a.set(4)
		expect(b.get()).toBe(4)
		expect(b.getDiffSince(startEpoch)).toEqual([1, 2])

		a.set(5)

		expect(() => b.get()).toThrowErrorMatchingInlineSnapshot(`"test"`)
		expect(b.getDiffSince(startEpoch)).toEqual(RESET_VALUE)
		const errorEpoch = getGlobalEpoch()

		a.set(6)
		expect(b.get()).toBe(6)
		expect(b.getDiffSince(errorEpoch)).toEqual(RESET_VALUE)
		expect(b.getDiffSince(errorEpoch + 1)).toEqual([])

		a.set(7)
		expect(b.get()).toBe(7)
		expect(b.getDiffSince(errorEpoch)).toEqual(RESET_VALUE)
		expect(b.getDiffSince(errorEpoch + 1)).toEqual([1])
	})
})

test('haveParentsChanged will not throw if one of the parents is throwing', () => {
	const a = atom('', 1)
	const scheduler = new EffectScheduler('', () => {
		a.get()
		throw new Error('test')
	})
	expect(() => {
		scheduler.attach()
		scheduler.execute()
	}).toThrowErrorMatchingInlineSnapshot(`"test"`)

	expect(haveParentsChanged(scheduler)).toBe(false)

	expect(() => a.set(2)).toThrowErrorMatchingInlineSnapshot(`"test"`)

	// haveParentsChanged should still be false because it already
	// executed the effect and it errored
	expect(haveParentsChanged(scheduler)).toBe(false)
})