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null.go
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null.go
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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package types
import (
"github.com/golang/protobuf/proto"
"github.com/golang/protobuf/ptypes"
"github.com/golang/protobuf/ptypes/struct"
"github.com/google/cel-go/common/types/ref"
"reflect"
)
// Null type implementation.
type Null structpb.NullValue
var (
// NullType singleton.
NullType = NewTypeValue("null_type")
// NullValue singleton.
NullValue = Null(structpb.NullValue_NULL_VALUE)
)
func (n Null) ConvertToNative(typeDesc reflect.Type) (interface{}, error) {
switch typeDesc.Kind() {
case reflect.Ptr:
switch typeDesc {
case jsonValueType:
return &structpb.Value{
Kind: &structpb.Value_NullValue{
NullValue: structpb.NullValue_NULL_VALUE}}, nil
case anyValueType:
pb, err := n.ConvertToNative(jsonValueType)
if err != nil {
return nil, err
}
return ptypes.MarshalAny(pb.(proto.Message))
}
case reflect.Interface:
if reflect.TypeOf(n).Implements(typeDesc) {
return n, nil
}
}
// By default return 'null'.
// TODO: determine whether there are other valid conversions for `null`.
return structpb.NullValue_NULL_VALUE, nil
}
func (n Null) ConvertToType(typeVal ref.Type) ref.Value {
if typeVal == StringType {
return String("null")
}
if typeVal == NullType {
return n
}
return NewErr("type conversion error from '%s' to '%s'", NullType, typeVal)
}
func (n Null) Equal(other ref.Value) ref.Value {
return Bool(NullType == other.Type())
}
func (n Null) Type() ref.Type {
return NullType
}
func (n Null) Value() interface{} {
return structpb.NullValue_NULL_VALUE
}