| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | * |
| 7 | * @emails react-core |
| 8 | * @jest-environment node |
| 9 | */ |
| 10 | |
| 11 | let React; |
| 12 | let ReactNoop; |
| 13 | let Scheduler; |
| 14 | let act; |
| 15 | let assertConsoleErrorDev; |
| 16 | let assertLog; |
| 17 | let useMemo; |
| 18 | let useState; |
| 19 | let useMemoCache; |
| 20 | let MemoCacheSentinel; |
| 21 | let ErrorBoundary; |
| 22 | |
| 23 | describe('useMemoCache()', () => { |
| 24 | beforeEach(() => { |
| 25 | jest.resetModules(); |
| 26 | |
| 27 | React = require('react'); |
| 28 | ReactNoop = require('react-noop-renderer'); |
| 29 | Scheduler = require('scheduler'); |
| 30 | const InternalTestUtils = require('internal-test-utils'); |
| 31 | act = InternalTestUtils.act; |
| 32 | assertConsoleErrorDev = InternalTestUtils.assertConsoleErrorDev; |
| 33 | assertLog = InternalTestUtils.assertLog; |
| 34 | useMemo = React.useMemo; |
| 35 | useMemoCache = require('react/compiler-runtime').c; |
| 36 | useState = React.useState; |
| 37 | MemoCacheSentinel = Symbol.for('react.memo_cache_sentinel'); |
| 38 | |
| 39 | class _ErrorBoundary extends React.Component { |
| 40 | constructor(props) { |
| 41 | super(props); |
| 42 | this.state = {hasError: false}; |
| 43 | } |
| 44 | |
| 45 | static getDerivedStateFromError(error) { |
| 46 | // Update state so the next render will show the fallback UI. |
| 47 | return {hasError: true}; |
| 48 | } |
| 49 | |
| 50 | componentDidCatch(error, errorInfo) {} |
| 51 | |
| 52 | render() { |
| 53 | if (this.state.hasError) { |
| 54 | // You can render any custom fallback UI |
| 55 | return <h1>Something went wrong.</h1>; |
| 56 | } |
| 57 | |
| 58 | return this.props.children; |
| 59 | } |
| 60 | } |
| 61 | ErrorBoundary = _ErrorBoundary; |
| 62 | }); |
| 63 | |
| 64 | it('render component using cache', async () => { |
| 65 | function Component(props) { |
| 66 | const cache = useMemoCache(1); |
| 67 | expect(Array.isArray(cache)).toBe(true); |
| 68 | expect(cache.length).toBe(1); |
| 69 | expect(cache[0]).toBe(MemoCacheSentinel); |
| 70 | |
| 71 | return 'Ok'; |
| 72 | } |
| 73 | const root = ReactNoop.createRoot(); |
| 74 | await act(() => { |
| 75 | root.render(<Component />); |
| 76 | }); |
| 77 | expect(root).toMatchRenderedOutput('Ok'); |
| 78 | }); |
| 79 | |
| 80 | it('update component using cache', async () => { |
| 81 | let setX; |
| 82 | let forceUpdate; |
| 83 | function Component(props) { |
| 84 | const cache = useMemoCache(5); |
| 85 | |
| 86 | // x is used to produce a `data` object passed to the child |
| 87 | const [x, _setX] = useState(0); |
| 88 | setX = _setX; |
| 89 | |
| 90 | // n is passed as-is to the child as a cache breaker |
| 91 | const [n, setN] = useState(0); |
| 92 | forceUpdate = () => setN(a => a + 1); |
| 93 | |
| 94 | const c_0 = x !== cache[0]; |
| 95 | let data; |
| 96 | if (c_0) { |
| 97 | data = {text: `Count ${x}`}; |
| 98 | cache[0] = x; |
| 99 | cache[1] = data; |
| 100 | } else { |
| 101 | data = cache[1]; |
| 102 | } |
| 103 | const c_2 = x !== cache[2]; |
| 104 | const c_3 = n !== cache[3]; |
| 105 | let t0; |
| 106 | if (c_2 || c_3) { |
| 107 | t0 = <Text data={data} n={n} />; |
| 108 | cache[2] = x; |
| 109 | cache[3] = n; |
| 110 | cache[4] = t0; |
| 111 | } else { |
| 112 | t0 = cache[4]; |
| 113 | } |
| 114 | return t0; |
| 115 | } |
| 116 | let data; |
| 117 | const Text = jest.fn(function Text(props) { |
| 118 | data = props.data; |
| 119 | return data.text; |
| 120 | }); |
| 121 | |
| 122 | const root = ReactNoop.createRoot(); |
| 123 | await act(() => { |
| 124 | root.render(<Component />); |
| 125 | }); |
| 126 | expect(root).toMatchRenderedOutput('Count 0'); |
| 127 | expect(Text).toHaveBeenCalledTimes(1); |
| 128 | const data0 = data; |
| 129 | |
| 130 | // Changing x should reset the data object |
| 131 | await act(() => { |
| 132 | setX(1); |
| 133 | }); |
| 134 | expect(root).toMatchRenderedOutput('Count 1'); |
| 135 | expect(Text).toHaveBeenCalledTimes(2); |
| 136 | expect(data).not.toBe(data0); |
| 137 | const data1 = data; |
| 138 | |
| 139 | // Forcing an unrelated update shouldn't recreate the |
| 140 | // data object. |
| 141 | await act(() => { |
| 142 | forceUpdate(); |
| 143 | }); |
| 144 | expect(root).toMatchRenderedOutput('Count 1'); |
| 145 | expect(Text).toHaveBeenCalledTimes(3); |
| 146 | expect(data).toBe(data1); // confirm that the cache persisted across renders |
| 147 | }); |
| 148 | |
| 149 | it('update component using cache with setstate during render', async () => { |
| 150 | let setN; |
| 151 | function Component(props) { |
| 152 | const cache = useMemoCache(5); |
| 153 | |
| 154 | // x is used to produce a `data` object passed to the child |
| 155 | const [x] = useState(0); |
| 156 | |
| 157 | const c_0 = x !== cache[0]; |
| 158 | let data; |
| 159 | if (c_0) { |
| 160 | data = {text: `Count ${x}`}; |
| 161 | cache[0] = x; |
| 162 | cache[1] = data; |
| 163 | } else { |
| 164 | data = cache[1]; |
| 165 | } |
| 166 | |
| 167 | // n is passed as-is to the child as a cache breaker |
| 168 | const [n, _setN] = useState(0); |
| 169 | setN = _setN; |
| 170 | |
| 171 | if (n === 1) { |
| 172 | setN(2); |
| 173 | return; |
| 174 | } |
| 175 | |
| 176 | const c_2 = x !== cache[2]; |
| 177 | const c_3 = n !== cache[3]; |
| 178 | let t0; |
| 179 | if (c_2 || c_3) { |
| 180 | t0 = <Text data={data} n={n} />; |
| 181 | cache[2] = x; |
| 182 | cache[3] = n; |
| 183 | cache[4] = t0; |
| 184 | } else { |
| 185 | t0 = cache[4]; |
| 186 | } |
| 187 | return t0; |
| 188 | } |
| 189 | let data; |
| 190 | const Text = jest.fn(function Text(props) { |
| 191 | data = props.data; |
| 192 | return `${data.text} (n=${props.n})`; |
| 193 | }); |
| 194 | |
| 195 | const root = ReactNoop.createRoot(); |
| 196 | await act(() => { |
| 197 | root.render(<Component />); |
| 198 | }); |
| 199 | expect(root).toMatchRenderedOutput('Count 0 (n=0)'); |
| 200 | expect(Text).toHaveBeenCalledTimes(1); |
| 201 | const data0 = data; |
| 202 | |
| 203 | // Trigger an update that will cause a setState during render. The `data` prop |
| 204 | // does not depend on `n`, and should remain cached. |
| 205 | await act(() => { |
| 206 | setN(1); |
| 207 | }); |
| 208 | expect(root).toMatchRenderedOutput('Count 0 (n=2)'); |
| 209 | expect(Text).toHaveBeenCalledTimes(2); |
| 210 | expect(data).toBe(data0); |
| 211 | }); |
| 212 | |
| 213 | it('update component using cache with throw during render', async () => { |
| 214 | let setN; |
| 215 | let shouldFail = true; |
| 216 | function Component(props) { |
| 217 | const cache = useMemoCache(5); |
| 218 | |
| 219 | // x is used to produce a `data` object passed to the child |
| 220 | const [x] = useState(0); |
| 221 | |
| 222 | const c_0 = x !== cache[0]; |
| 223 | let data; |
| 224 | if (c_0) { |
| 225 | data = {text: `Count ${x}`}; |
| 226 | cache[0] = x; |
| 227 | cache[1] = data; |
| 228 | } else { |
| 229 | data = cache[1]; |
| 230 | } |
| 231 | |
| 232 | // n is passed as-is to the child as a cache breaker |
| 233 | const [n, _setN] = useState(0); |
| 234 | setN = _setN; |
| 235 | |
| 236 | if (n === 1) { |
| 237 | if (shouldFail) { |
| 238 | shouldFail = false; |
| 239 | throw new Error('failed'); |
| 240 | } |
| 241 | } |
| 242 | |
| 243 | const c_2 = x !== cache[2]; |
| 244 | const c_3 = n !== cache[3]; |
| 245 | let t0; |
| 246 | if (c_2 || c_3) { |
| 247 | t0 = <Text data={data} n={n} />; |
| 248 | cache[2] = x; |
| 249 | cache[3] = n; |
| 250 | cache[4] = t0; |
| 251 | } else { |
| 252 | t0 = cache[4]; |
| 253 | } |
| 254 | return t0; |
| 255 | } |
| 256 | let data; |
| 257 | const Text = jest.fn(function Text(props) { |
| 258 | data = props.data; |
| 259 | return `${data.text} (n=${props.n})`; |
| 260 | }); |
| 261 | |
| 262 | const root = ReactNoop.createRoot(); |
| 263 | await act(() => { |
| 264 | root.render( |
| 265 | <ErrorBoundary> |
| 266 | <Component /> |
| 267 | </ErrorBoundary>, |
| 268 | ); |
| 269 | }); |
| 270 | expect(root).toMatchRenderedOutput('Count 0 (n=0)'); |
| 271 | expect(Text).toHaveBeenCalledTimes(1); |
| 272 | const data0 = data; |
| 273 | |
| 274 | await act(() => { |
| 275 | // this triggers a throw. |
| 276 | setN(1); |
| 277 | }); |
| 278 | assertConsoleErrorDev([ |
| 279 | 'Error: There was an error during concurrent rendering but React was able to recover by instead synchronously rendering the entire root.' + |
| 280 | '\n in <stack>', |
| 281 | ]); |
| 282 | expect(root).toMatchRenderedOutput('Count 0 (n=1)'); |
| 283 | expect(Text).toHaveBeenCalledTimes(2); |
| 284 | expect(data).toBe(data0); |
| 285 | const data1 = data; |
| 286 | |
| 287 | // Forcing an unrelated update shouldn't recreate the |
| 288 | // data object. |
| 289 | await act(() => { |
| 290 | setN(2); |
| 291 | }); |
| 292 | expect(root).toMatchRenderedOutput('Count 0 (n=2)'); |
| 293 | expect(Text).toHaveBeenCalledTimes(3); |
| 294 | expect(data).toBe(data1); // confirm that the cache persisted across renders |
| 295 | }); |
| 296 | |
| 297 | it('update component and custom hook with caches', async () => { |
| 298 | let setX; |
| 299 | let forceUpdate; |
| 300 | function Component(props) { |
| 301 | const cache = useMemoCache(4); |
| 302 | |
| 303 | // x is used to produce a `data` object passed to the child |
| 304 | const [x, _setX] = useState(0); |
| 305 | setX = _setX; |
| 306 | const c_x = x !== cache[0]; |
| 307 | cache[0] = x; |
| 308 | |
| 309 | // n is passed as-is to the child as a cache breaker |
| 310 | const [n, setN] = useState(0); |
| 311 | forceUpdate = () => setN(a => a + 1); |
| 312 | const c_n = n !== cache[1]; |
| 313 | cache[1] = n; |
| 314 | |
| 315 | let _data; |
| 316 | if (c_x) { |
| 317 | _data = cache[2] = {text: `Count ${x}`}; |
| 318 | } else { |
| 319 | _data = cache[2]; |
| 320 | } |
| 321 | const data = useData(_data); |
| 322 | if (c_x || c_n) { |
| 323 | return (cache[3] = <Text data={data} n={n} />); |
| 324 | } else { |
| 325 | return cache[3]; |
| 326 | } |
| 327 | } |
| 328 | function useData(data) { |
| 329 | const cache = useMemoCache(2); |
| 330 | const c_data = data !== cache[0]; |
| 331 | cache[0] = data; |
| 332 | let nextData; |
| 333 | if (c_data) { |
| 334 | nextData = cache[1] = {text: data.text.toLowerCase()}; |
| 335 | } else { |
| 336 | nextData = cache[1]; |
| 337 | } |
| 338 | return nextData; |
| 339 | } |
| 340 | let data; |
| 341 | const Text = jest.fn(function Text(props) { |
| 342 | data = props.data; |
| 343 | return data.text; |
| 344 | }); |
| 345 | |
| 346 | const root = ReactNoop.createRoot(); |
| 347 | await act(() => { |
| 348 | root.render(<Component />); |
| 349 | }); |
| 350 | expect(root).toMatchRenderedOutput('count 0'); |
| 351 | expect(Text).toHaveBeenCalledTimes(1); |
| 352 | const data0 = data; |
| 353 | |
| 354 | // Changing x should reset the data object |
| 355 | await act(() => { |
| 356 | setX(1); |
| 357 | }); |
| 358 | expect(root).toMatchRenderedOutput('count 1'); |
| 359 | expect(Text).toHaveBeenCalledTimes(2); |
| 360 | expect(data).not.toBe(data0); |
| 361 | const data1 = data; |
| 362 | |
| 363 | // Forcing an unrelated update shouldn't recreate the |
| 364 | // data object. |
| 365 | await act(() => { |
| 366 | forceUpdate(); |
| 367 | }); |
| 368 | expect(root).toMatchRenderedOutput('count 1'); |
| 369 | expect(Text).toHaveBeenCalledTimes(3); |
| 370 | expect(data).toBe(data1); // confirm that the cache persisted across renders |
| 371 | }); |
| 372 | |
| 373 | it('reuses computations from suspended/interrupted render attempts during an update', async () => { |
| 374 | // This test demonstrates the benefit of a shared memo cache. By "shared" I |
| 375 | // mean multiple concurrent render attempts of the same component/hook use |
| 376 | // the same cache. (When the feature flag is off, we don't do this — the |
| 377 | // cache is copy-on-write.) |
| 378 | // |
| 379 | // If an update is interrupted, either because it suspended or because of |
| 380 | // another update, we can reuse the memoized computations from the previous |
| 381 | // attempt. We can do this because the React Compiler performs atomic writes |
| 382 | // to the memo cache, i.e. it will not record the inputs to a memoization |
| 383 | // without also recording its output. |
| 384 | // |
| 385 | // This gives us a form of "resuming" within components and hooks. |
| 386 | // |
| 387 | // This only works when updating a component that already mounted. It has no |
| 388 | // impact during initial render, because the memo cache is stored on the |
| 389 | // fiber, and since we have not implemented resuming for fibers, it's always |
| 390 | // a fresh memo cache, anyway. |
| 391 | // |
| 392 | // However, this alone is pretty useful — it happens whenever you update the |
| 393 | // UI with fresh data after a mutation/action, which is extremely common in |
| 394 | // a Suspense-driven (e.g. RSC or Relay) app. That's the scenario that this |
| 395 | // test simulates. |
| 396 | // |
| 397 | // So the impact of this feature is faster data mutations/actions. |
| 398 | |
| 399 | function someExpensiveProcessing(t) { |
| 400 | Scheduler.log(`Some expensive processing... [${t}]`); |
| 401 | return t; |
| 402 | } |
| 403 | |
| 404 | function useWithLog(t, msg) { |
| 405 | try { |
| 406 | return React.use(t); |
| 407 | } catch (x) { |
| 408 | Scheduler.log(`Suspend! [${msg}]`); |
| 409 | throw x; |
| 410 | } |
| 411 | } |
| 412 | |
| 413 | // Original code: |
| 414 | // |
| 415 | // function Data({chunkA, chunkB}) { |
| 416 | // const a = someExpensiveProcessing(useWithLog(chunkA, 'chunkA')); |
| 417 | // const b = useWithLog(chunkB, 'chunkB'); |
| 418 | // return ( |
| 419 | // <> |
| 420 | // {a} |
| 421 | // {b} |
| 422 | // </> |
| 423 | // ); |
| 424 | // } |
| 425 | // |
| 426 | // function Input() { |
| 427 | // const [input, _setText] = useState(''); |
| 428 | // return input; |
| 429 | // } |
| 430 | // |
| 431 | // function App({chunkA, chunkB}) { |
| 432 | // return ( |
| 433 | // <> |
| 434 | // <div> |
| 435 | // Input: <Input /> |
| 436 | // </div> |
| 437 | // <div> |
| 438 | // Data: <Data chunkA={chunkA} chunkB={chunkB} /> |
| 439 | // </div> |
| 440 | // </> |
| 441 | // ); |
| 442 | // } |
| 443 | function Data(t0) { |
| 444 | const $ = useMemoCache(5); |
| 445 | const {chunkA, chunkB} = t0; |
| 446 | const t1 = useWithLog(chunkA, 'chunkA'); |
| 447 | let t2; |
| 448 | |
| 449 | if ($[0] !== t1) { |
| 450 | t2 = someExpensiveProcessing(t1); |
| 451 | $[0] = t1; |
| 452 | $[1] = t2; |
| 453 | } else { |
| 454 | t2 = $[1]; |
| 455 | } |
| 456 | |
| 457 | const a = t2; |
| 458 | const b = useWithLog(chunkB, 'chunkB'); |
| 459 | let t3; |
| 460 | |
| 461 | if ($[2] !== a || $[3] !== b) { |
| 462 | t3 = ( |
| 463 | <> |
| 464 | {a} |
| 465 | {b} |
| 466 | </> |
| 467 | ); |
| 468 | $[2] = a; |
| 469 | $[3] = b; |
| 470 | $[4] = t3; |
| 471 | } else { |
| 472 | t3 = $[4]; |
| 473 | } |
| 474 | |
| 475 | return t3; |
| 476 | } |
| 477 | |
| 478 | let setInput; |
| 479 | function Input() { |
| 480 | const [input, _set] = useState(''); |
| 481 | setInput = _set; |
| 482 | return input; |
| 483 | } |
| 484 | |
| 485 | function App(t0) { |
| 486 | const $ = useMemoCache(4); |
| 487 | const {chunkA, chunkB} = t0; |
| 488 | let t1; |
| 489 | |
| 490 | if ($[0] === Symbol.for('react.memo_cache_sentinel')) { |
| 491 | t1 = ( |
| 492 | <div> |
| 493 | Input: <Input /> |
| 494 | </div> |
| 495 | ); |
| 496 | $[0] = t1; |
| 497 | } else { |
| 498 | t1 = $[0]; |
| 499 | } |
| 500 | |
| 501 | let t2; |
| 502 | |
| 503 | if ($[1] !== chunkA || $[2] !== chunkB) { |
| 504 | t2 = ( |
| 505 | <> |
| 506 | {t1} |
| 507 | <div> |
| 508 | Data: <Data chunkA={chunkA} chunkB={chunkB} /> |
| 509 | </div> |
| 510 | </> |
| 511 | ); |
| 512 | $[1] = chunkA; |
| 513 | $[2] = chunkB; |
| 514 | $[3] = t2; |
| 515 | } else { |
| 516 | t2 = $[3]; |
| 517 | } |
| 518 | |
| 519 | return t2; |
| 520 | } |
| 521 | |
| 522 | function createInstrumentedResolvedPromise(value) { |
| 523 | return { |
| 524 | then() {}, |
| 525 | status: 'fulfilled', |
| 526 | value, |
| 527 | }; |
| 528 | } |
| 529 | |
| 530 | function createDeferred() { |
| 531 | let resolve; |
| 532 | const p = new Promise(res => { |
| 533 | resolve = res; |
| 534 | }); |
| 535 | p.resolve = resolve; |
| 536 | return p; |
| 537 | } |
| 538 | |
| 539 | // Initial render. We pass the data in as two separate "chunks" to simulate |
| 540 | // a stream (e.g. RSC). |
| 541 | const root = ReactNoop.createRoot(); |
| 542 | const initialChunkA = createInstrumentedResolvedPromise('A1'); |
| 543 | const initialChunkB = createInstrumentedResolvedPromise('B1'); |
| 544 | await act(() => |
| 545 | root.render(<App chunkA={initialChunkA} chunkB={initialChunkB} />), |
| 546 | ); |
| 547 | assertLog(['Some expensive processing... [A1]']); |
| 548 | expect(root).toMatchRenderedOutput( |
| 549 | <> |
| 550 | <div>Input: </div> |
| 551 | <div>Data: A1B1</div> |
| 552 | </>, |
| 553 | ); |
| 554 | |
| 555 | // Update the UI in a transition. This would happen after a data mutation. |
| 556 | const updatedChunkA = createDeferred(); |
| 557 | const updatedChunkB = createDeferred(); |
| 558 | await act(() => { |
| 559 | React.startTransition(() => { |
| 560 | root.render(<App chunkA={updatedChunkA} chunkB={updatedChunkB} />); |
| 561 | }); |
| 562 | }); |
| 563 | assertLog(['Suspend! [chunkA]']); |
| 564 | |
| 565 | // The data starts to stream in. Loading the data in the first chunk |
| 566 | // triggers an expensive computation in the UI. Later, we'll test whether |
| 567 | // this computation is reused. |
| 568 | await act(() => updatedChunkA.resolve('A2')); |
| 569 | assertLog(['Some expensive processing... [A2]', 'Suspend! [chunkB]']); |
| 570 | |
| 571 | // The second chunk hasn't loaded yet, so we're still showing the |
| 572 | // initial UI. |
| 573 | expect(root).toMatchRenderedOutput( |
| 574 | <> |
| 575 | <div>Input: </div> |
| 576 | <div>Data: A1B1</div> |
| 577 | </>, |
| 578 | ); |
| 579 | |
| 580 | // While waiting for the data to finish loading, update a different part of |
| 581 | // the screen. This interrupts the refresh transition. |
| 582 | // |
| 583 | // In a real app, this might be an input or hover event. |
| 584 | await act(() => setInput('hi!')); |
| 585 | |
| 586 | // Once the input has updated, we go back to rendering the transition. |
| 587 | if (gate(flags => flags.enableNoCloningMemoCache)) { |
| 588 | // We did not have process the first chunk again. We reused the |
| 589 | // computation from the earlier attempt. |
| 590 | assertLog(['Suspend! [chunkB]']); |
| 591 | } else { |
| 592 | // Because we clone/reset the memo cache after every aborted attempt, we |
| 593 | // must process the first chunk again. |
| 594 | assertLog(['Some expensive processing... [A2]', 'Suspend! [chunkB]']); |
| 595 | } |
| 596 | |
| 597 | expect(root).toMatchRenderedOutput( |
| 598 | <> |
| 599 | <div>Input: hi!</div> |
| 600 | <div>Data: A1B1</div> |
| 601 | </>, |
| 602 | ); |
| 603 | |
| 604 | // Finish loading the data. |
| 605 | await act(() => updatedChunkB.resolve('B2')); |
| 606 | if (gate(flags => flags.enableNoCloningMemoCache)) { |
| 607 | // We did not have process the first chunk again. We reused the |
| 608 | // computation from the earlier attempt. |
| 609 | assertLog([]); |
| 610 | } else { |
| 611 | // Because we clone/reset the memo cache after every aborted attempt, we |
| 612 | // must process the first chunk again. |
| 613 | // |
| 614 | // That's three total times we've processed the first chunk, compared to |
| 615 | // just once when enableNoCloningMemoCache is on. |
| 616 | assertLog(['Some expensive processing... [A2]']); |
| 617 | } |
| 618 | expect(root).toMatchRenderedOutput( |
| 619 | <> |
| 620 | <div>Input: hi!</div> |
| 621 | <div>Data: A2B2</div> |
| 622 | </>, |
| 623 | ); |
| 624 | }); |
| 625 | |
| 626 | it('(repro) infinite renders when used with setState during render', async () => { |
| 627 | // Output of react compiler on `useUserMemo` |
| 628 | function useCompilerMemo(value) { |
| 629 | let arr; |
| 630 | const $ = useMemoCache(2); |
| 631 | if ($[0] !== value) { |
| 632 | arr = [value]; |
| 633 | $[0] = value; |
| 634 | $[1] = arr; |
| 635 | } else { |
| 636 | arr = $[1]; |
| 637 | } |
| 638 | return arr; |
| 639 | } |
| 640 | |
| 641 | // Baseline / source code |
| 642 | function useManualMemo(value) { |
| 643 | return useMemo(() => [value], [value]); |
| 644 | } |
| 645 | |
| 646 | function makeComponent(hook) { |
| 647 | return function Component({value}) { |
| 648 | const state = hook(value); |
| 649 | const [prevState, setPrevState] = useState(null); |
| 650 | if (state !== prevState) { |
| 651 | setPrevState(state); |
| 652 | } |
| 653 | return <div>{state.join(',')}</div>; |
| 654 | }; |
| 655 | } |
| 656 | |
| 657 | /** |
| 658 | * Test with useMemoCache |
| 659 | */ |
| 660 | let root = ReactNoop.createRoot(); |
| 661 | const CompilerMemoComponent = makeComponent(useCompilerMemo); |
| 662 | await act(() => { |
| 663 | root.render(<CompilerMemoComponent value={2} />); |
| 664 | }); |
| 665 | expect(root).toMatchRenderedOutput(<div>2</div>); |
| 666 | |
| 667 | /** |
| 668 | * Test with useMemo |
| 669 | */ |
| 670 | root = ReactNoop.createRoot(); |
| 671 | const HookMemoComponent = makeComponent(useManualMemo); |
| 672 | await act(() => { |
| 673 | root.render(<HookMemoComponent value={2} />); |
| 674 | }); |
| 675 | expect(root).toMatchRenderedOutput(<div>2</div>); |
| 676 | }); |
| 677 | }); |