[compiler] Repro for imprecise memo due to closure capturing changes

Syncing this stack internally there is a small percentage of files that lose memoization, generally for callbacks. The repro here tries to get at the core pattern, where a parameter escapes into a mutable return value. This makes the callback appear mutable, and means that calls like array.map aren't able to optimize as well — even if the array itself is transitively immutable.

The challenge is that we can't really distinguish between just capturing and true mutation right now — AnalyzeFunctions kind of has to pick one, and consider both a mutation.

ghstack-source-id: 55efdd1b13
Pull Request resolved: https://github.com/facebook/react/pull/33180

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-separate-memoization-due-to-callback-capturing.expect.md

@@ -0,0 +1,171 @@
+
+## Input
+
+```javascript
+import {ValidateMemoization} from 'shared-runtime';
+
+const Codes = {
+  en: {name: 'English'},
+  ja: {name: 'Japanese'},
+  ko: {name: 'Korean'},
+  zh: {name: 'Chinese'},
+};
+
+function Component(a) {
+  let keys;
+  if (a) {
+    keys = Object.keys(Codes);
+  } else {
+    return null;
+  }
+  const options = keys.map(code => {
+    const country = Codes[code];
+    return {
+      name: country.name,
+      code,
+    };
+  });
+  return (
+    <>
+      <ValidateMemoization inputs={[]} output={keys} onlyCheckCompiled={true} />
+      <ValidateMemoization
+        inputs={[]}
+        output={options}
+        onlyCheckCompiled={true}
+      />
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{a: false}],
+  sequentialRenders: [
+    {a: false},
+    {a: true},
+    {a: true},
+    {a: false},
+    {a: true},
+    {a: false},
+  ],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { ValidateMemoization } from "shared-runtime";
+
+const Codes = {
+  en: { name: "English" },
+  ja: { name: "Japanese" },
+  ko: { name: "Korean" },
+  zh: { name: "Chinese" },
+};
+
+function Component(a) {
+  const $ = _c(13);
+  let keys;
+  let t0;
+  let t1;
+  if ($[0] !== a) {
+    t1 = Symbol.for("react.early_return_sentinel");
+    bb0: {
+      if (a) {
+        keys = Object.keys(Codes);
+      } else {
+        t1 = null;
+        break bb0;
+      }
+
+      t0 = keys.map(_temp);
+    }
+    $[0] = a;
+    $[1] = t0;
+    $[2] = t1;
+    $[3] = keys;
+  } else {
+    t0 = $[1];
+    t1 = $[2];
+    keys = $[3];
+  }
+  if (t1 !== Symbol.for("react.early_return_sentinel")) {
+    return t1;
+  }
+  const options = t0;
+  let t2;
+  if ($[4] === Symbol.for("react.memo_cache_sentinel")) {
+    t2 = [];
+    $[4] = t2;
+  } else {
+    t2 = $[4];
+  }
+  let t3;
+  if ($[5] !== keys) {
+    t3 = (
+      <ValidateMemoization inputs={t2} output={keys} onlyCheckCompiled={true} />
+    );
+    $[5] = keys;
+    $[6] = t3;
+  } else {
+    t3 = $[6];
+  }
+  let t4;
+  if ($[7] === Symbol.for("react.memo_cache_sentinel")) {
+    t4 = [];
+    $[7] = t4;
+  } else {
+    t4 = $[7];
+  }
+  let t5;
+  if ($[8] !== options) {
+    t5 = (
+      <ValidateMemoization
+        inputs={t4}
+        output={options}
+        onlyCheckCompiled={true}
+      />
+    );
+    $[8] = options;
+    $[9] = t5;
+  } else {
+    t5 = $[9];
+  }
+  let t6;
+  if ($[10] !== t3 || $[11] !== t5) {
+    t6 = (
+      <>
+        {t3}
+        {t5}
+      </>
+    );
+    $[10] = t3;
+    $[11] = t5;
+    $[12] = t6;
+  } else {
+    t6 = $[12];
+  }
+  return t6;
+}
+function _temp(code) {
+  const country = Codes[code];
+  return { name: country.name, code };
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ a: false }],
+  sequentialRenders: [
+    { a: false },
+    { a: true },
+    { a: true },
+    { a: false },
+    { a: true },
+    { a: false },
+  ],
+};
+
+```
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-separate-memoization-due-to-callback-capturing.js

@@ -0,0 +1,47 @@
+import {ValidateMemoization} from 'shared-runtime';
+
+const Codes = {
+  en: {name: 'English'},
+  ja: {name: 'Japanese'},
+  ko: {name: 'Korean'},
+  zh: {name: 'Chinese'},
+};
+
+function Component(a) {
+  let keys;
+  if (a) {
+    keys = Object.keys(Codes);
+  } else {
+    return null;
+  }
+  const options = keys.map(code => {
+    const country = Codes[code];
+    return {
+      name: country.name,
+      code,
+    };
+  });
+  return (
+    <>
+      <ValidateMemoization inputs={[]} output={keys} onlyCheckCompiled={true} />
+      <ValidateMemoization
+        inputs={[]}
+        output={options}
+        onlyCheckCompiled={true}
+      />
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{a: false}],
+  sequentialRenders: [
+    {a: false},
+    {a: true},
+    {a: true},
+    {a: false},
+    {a: true},
+    {a: false},
+  ],
+};

compiler/packages/snap/src/SproutTodoFilter.ts

@@ -483,6 +483,7 @@ const skipFilter = new Set([
   'todo.lower-context-access-array-destructuring',
   'lower-context-selector-simple',
   'lower-context-acess-multiple',
+  'bug-separate-memoization-due-to-callback-capturing',
 ]);
 
 export default skipFilter;