Method PreVisitSelect

eval/compiler/flat_expr_builder.cc:901–944

  }

  void PreVisitSelect(const cel::Expr& expr,
                      const cel::SelectExpr& select_expr) override {
    if (!progress_status_.ok()) {
      return;
    }
    if (!ValidateOrError(
            !select_expr.field().empty(),
            "invalid expression: select 'field' must not be empty")) {
      return;
    }
    if (!ValidateOrError(
            select_expr.has_operand() &&
                select_expr.operand().kind_case() !=
                    cel::ExprKindCase::kUnspecifiedExpr,
            "invalid expression: select must specify an operand")) {
      return;
    }

    // Not exactly the cleanest solution - we peek into child of
    // select_expr.
    // Chain of multiple SELECT ending with IDENT can represent namespaced
    // entity.
    if (!select_expr.test_only() && (select_expr.operand().has_ident_expr() ||
                                     select_expr.operand().has_select_expr())) {
      // select expressions are pushed in reverse order:
      // google.type.Expr is pushed as:
      // - field: 'Expr'
      // - field: 'type'
      // - id: 'google'
      //
      // The search order though is as follows:
      // - id: 'google.type.Expr'
      // - id: 'google.type', field: 'Expr'
      // - id: 'google', field: 'type', field: 'Expr'
      for (size_t i = 0; i < namespace_stack_.size(); i++) {
        auto ns = namespace_stack_[i];
        namespace_stack_[i] = {
            ns.first, absl::StrCat(select_expr.field(), ".", ns.second)};
      }
      namespace_stack_.push_back({&expr, select_expr.field()});
    } else {
      namespace_stack_.clear();
    }
  }

  // Select node handler.
  // Invoked after child nodes are processed.