computeMemoizedIdentifiers() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneNonEscapingScopes.ts lines 280–347

function computeMemoizedIdentifiers(state: State): Set<DeclarationId> {
  const memoized = new Set<DeclarationId>();

  // Visit an identifier, optionally forcing it to be memoized
  function visit(id: DeclarationId, forceMemoize: boolean = false): boolean {
    const node = state.identifiers.get(id);
    CompilerError.invariant(node !== undefined, {
      reason: `Expected a node for all identifiers, none found for \`${id}\``,
      loc: GeneratedSource,
    });
    if (node.seen) {
      return node.memoized;
    }
    node.seen = true;

    /*
     * Note: in case of cycles we temporarily mark the identifier as non-memoized,
     * this is reset later after processing dependencies
     */
    node.memoized = false;

    // Visit dependencies, determine if any of them are memoized
    let hasMemoizedDependency = false;
    for (const dep of node.dependencies) {
      const isDepMemoized = visit(dep);
      hasMemoizedDependency ||= isDepMemoized;
    }

    if (
      node.level === MemoizationLevel.Memoized ||
      (node.level === MemoizationLevel.Conditional &&
        (hasMemoizedDependency || forceMemoize)) ||
      (node.level === MemoizationLevel.Unmemoized && forceMemoize)
    ) {
      node.memoized = true;
      memoized.add(id);
      for (const scope of node.scopes) {
        forceMemoizeScopeDependencies(scope);
      }
    }
    return node.memoized;
  }

  // Force all the scope's optionally-memoizeable dependencies (not "Never") to be memoized
  function forceMemoizeScopeDependencies(id: ScopeId): void {
    const node = state.scopes.get(id);
    CompilerError.invariant(node !== undefined, {
      reason: 'Expected a node for all scopes',
      loc: GeneratedSource,
    });
    if (node.seen) {
      return;
    }
    node.seen = true;

    for (const dep of node.dependencies) {
      visit(dep, true);
    }
    return;
  }

  // Walk from the "roots" aka returned identifiers.
  for (const value of state.escapingValues) {
    visit(value);
  }

  return memoized;
}