visitBlock() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/MergeReactiveScopesThatInvalidateTogether.ts lines 145–398

  override visitBlock(
    block: ReactiveBlock,
    state: ReactiveScopeDependencies | null,
  ): void {
    // Pass 1: visit nested blocks to potentially merge their scopes
    this.traverseBlock(block, state);

    // Pass 2: identify scopes for merging
    type MergedScope = {
      block: ReactiveScopeBlock;
      from: number;
      to: number;
      lvalues: Set<DeclarationId>;
    };
    let current: MergedScope | null = null;
    const merged: Array<MergedScope> = [];
    function reset(): void {
      CompilerError.invariant(current !== null, {
        reason:
          'MergeConsecutiveScopes: expected current scope to be non-null if reset()',
        loc: GeneratedSource,
      });
      if (current.to > current.from + 1) {
        merged.push(current);
      }
      current = null;
    }
    for (let i = 0; i < block.length; i++) {
      const instr = block[i]!;
      switch (instr.kind) {
        case 'terminal': {
          // For now we don't merge across terminals
          if (current !== null) {
            log(
              `Reset scope @${current.block.scope.id} from terminal [${instr.terminal.id}]`,
            );
            reset();
          }
          break;
        }
        case 'pruned-scope': {
          // For now we don't merge across pruned scopes
          if (current !== null) {
            log(
              `Reset scope @${current.block.scope.id} from pruned scope @${instr.scope.id}`,
            );
            reset();
          }
          break;
        }
        case 'instruction': {
          switch (instr.instruction.value.kind) {
            case 'BinaryExpression':
            case 'ComputedLoad':
            case 'JSXText':
            case 'LoadGlobal':
            case 'LoadLocal':
            case 'Primitive':
            case 'PropertyLoad':
            case 'TemplateLiteral':
            case 'UnaryExpression': {
              /*
               * We can merge two scopes if there are intervening instructions, but:
               * - Only if the instructions are simple and it's okay to make them
               *   execute conditionally (hence allowing a conservative subset of value kinds)
               * - The values produced are used at or before the next scope. If they are used
               *   later and we move them into the scope, then they wouldn't be accessible to
               *   subsequent code wo expanding the set of declarations, which we want to avoid
               */
              if (current !== null && instr.instruction.lvalue !== null) {
                current.lvalues.add(
                  instr.instruction.lvalue.identifier.declarationId,
                );
                if (instr.instruction.value.kind === 'LoadLocal') {
                  this.temporaries.set(
                    instr.instruction.lvalue.identifier.declarationId,
                    instr.instruction.value.place.identifier.declarationId,
                  );
                }
              }
              break;