Method PostVisitRewrite

extensions/select_optimization.cc:448–490

  }

  bool PostVisitRewrite(Expr& expr) override {
    if (!progress_status_.ok()) {
      return false;
    }
    path_.pop_back();
    auto candidate_iter = candidates_.find(&expr);
    if (candidate_iter == candidates_.end()) {
      return false;
    }

    // On post visit, filter candidates that aren't rooted on a message or a
    // select chain.
    const QualifierInstruction& candidate = candidate_iter->second;
    if (!HasOptimizeableRoot(&expr, candidate)) {
      candidates_.erase(candidate_iter);
      return false;
    }

    if (!path_.empty() && candidates_.find(path_.back()) != candidates_.end()) {
      // parent is optimizeable, defer rewriting until we consider the parent.
      return false;
    }

    SelectPath path = GetSelectPath(&expr);

    // generate the new cel.attribute call.
    absl::string_view fn = path.test_only ? kCelHasField : kCelAttribute;

    Expr operand(std::move(*path.operand));
    Expr call;
    call.set_id(expr.id());
    call.mutable_call_expr().set_function(std::string(fn));
    call.mutable_call_expr().mutable_args().reserve(2);

    call.mutable_call_expr().mutable_args().push_back(std::move(operand));
    call.mutable_call_expr().mutable_args().push_back(
        MakeSelectPathExpr(path.select_instructions));

    // TODO(uncreated-issue/54): support for optionals.
    expr = std::move(call);

    return true;
  }

  absl::Status GetProgressStatus() const { return progress_status_; }