[compiler] Inferred deps must match exact optionality of manual deps

To prevent any difference in behavior, we check that the optionality of the inferred deps exactly matches the optionality of the manual dependencies. This required a fix, I was incorrectly inferring optionality of manual deps (they're only optional if OptionalTerminal.optional is true) - for nested cases of mixed optional/non-optional.

[ghstack-poisoned]

Author: josephsavona

compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts

@@ -488,7 +488,7 @@ export function dropManualMemoization(func: HIRFunction): void {
 function findOptionalPlaces(fn: HIRFunction): Set<IdentifierId> {
   const optionals = new Set<IdentifierId>();
   for (const [, block] of fn.body.blocks) {
-    if (block.terminal.kind === 'optional') {
+    if (block.terminal.kind === 'optional' && block.terminal.optional) {
       const optionalTerminal = block.terminal;
       let testBlock = fn.body.blocks.get(block.terminal.test)!;
       loop: while (true) {

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidatePreservedManualMemoization.ts

@@ -170,7 +170,7 @@ function compareDeps(
     if (inferred.path[i].property !== source.path[i].property) {
       isSubpath = false;
       break;
-    } else if (inferred.path[i].optional && !source.path[i].optional) {
+    } else if (inferred.path[i].optional !== source.path[i].optional) {
       /**
        * The inferred path must be at least as precise as the manual path:
        * if the inferred path is optional, then the source path must have

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-optional-member-expression-as-memo-dep-non-optional-in-body.expect.md

@@ -0,0 +1,38 @@
+
+## Input
+
+```javascript
+// @validatePreserveExistingMemoizationGuarantees
+function Component(props) {
+  const data = useMemo(() => {
+    // actual code is non-optional
+    return props.items.edges.nodes ?? [];
+    // deps are optional
+  }, [props.items?.edges?.nodes]);
+  return <Foo data={data} />;
+}
+
+```
+
+
+## Error
+
+```
+   1 | // @validatePreserveExistingMemoizationGuarantees
+   2 | function Component(props) {
+>  3 |   const data = useMemo(() => {
+     |                        ^^^^^^^
+>  4 |     // actual code is non-optional
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>  5 |     return props.items.edges.nodes ?? [];
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>  6 |     // deps are optional
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>  7 |   }, [props.items?.edges?.nodes]);
+     | ^^^^ CannotPreserveMemoization: React Compiler has skipped optimizing this component because the existing manual memoization could not be preserved. The inferred dependencies did not match the manually specified dependencies, which could cause the value to change more or less frequently than expected (3:7)
+   8 |   return <Foo data={data} />;
+   9 | }
+  10 |
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/optional-member-expression-as-memo-dep-non-optional-in-body.js renamed to compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-optional-member-expression-as-memo-dep-non-optional-in-body.js

@@ -10,8 +10,8 @@ function Component(props) {
     x.push(props?.items);
     x.push(props.items);
     return x;
-  }, [props?.items]);
-  return <ValidateMemoization inputs={[props?.items]} output={data} />;
+  }, [props.items]);
+  return <ValidateMemoization inputs={[props.items]} output={data} />;
 }
 
 ```
@@ -23,8 +23,6 @@ import { c as _c } from "react/compiler-runtime"; // @validatePreserveExistingMe
 import { ValidateMemoization } from "shared-runtime";
 function Component(props) {
   const $ = _c(7);
-
-  props?.items;
   let t0;
   let x;
   if ($[0] !== props.items) {
@@ -38,25 +36,24 @@ function Component(props) {
   }
   t0 = x;
   const data = t0;
-  const t1 = props?.items;
-  let t2;
-  if ($[2] !== t1) {
-    t2 = [t1];
-    $[2] = t1;
-    $[3] = t2;
+  let t1;
+  if ($[2] !== props.items) {
+    t1 = [props.items];
+    $[2] = props.items;
+    $[3] = t1;
   } else {
-    t2 = $[3];
+    t1 = $[3];
   }
-  let t3;
-  if ($[4] !== t2 || $[5] !== data) {
-    t3 = <ValidateMemoization inputs={t2} output={data} />;
-    $[4] = t2;
+  let t2;
+  if ($[4] !== t1 || $[5] !== data) {
+    t2 = <ValidateMemoization inputs={t1} output={data} />;
+    $[4] = t1;
     $[5] = data;
-    $[6] = t3;
+    $[6] = t2;
   } else {
-    t3 = $[6];
+    t2 = $[6];
   }
-  return t3;
+  return t2;
 }
 
 ```

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/optional-member-expression-as-memo-dep-non-optional-in-body.expect.md

@@ -6,6 +6,6 @@ function Component(props) {
     x.push(props?.items);
     x.push(props.items);
     return x;
-  }, [props?.items]);
-  return <ValidateMemoization inputs={[props?.items]} output={data} />;
+  }, [props.items]);
+  return <ValidateMemoization inputs={[props.items]} output={data} />;
 }