go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/proto/protowalk/processor_output_only.go (about)

     1  // Copyright 2022 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package protowalk
    16  
    17  import (
    18  	"google.golang.org/genproto/googleapis/api/annotations"
    19  	"google.golang.org/protobuf/proto"
    20  	"google.golang.org/protobuf/reflect/protoreflect"
    21  	"google.golang.org/protobuf/types/descriptorpb"
    22  )
    23  
    24  // OutputOnlyProcessor implements the recommended behavior of
    25  // aip.dev/203#output-only, namely that fields marked like:
    26  //
    27  //	type name = <tag> [(google.api.field_behavior) = OUTPUT_ONLY];
    28  //
    29  // Should be cleared by the server (without raising an error) if
    30  // a user request includes a value for them.
    31  type OutputOnlyProcessor struct{}
    32  
    33  var _ FieldProcessor = (*OutputOnlyProcessor)(nil)
    34  
    35  // Process implements FieldProcessor.
    36  //
    37  // This will clear (zero) the field in `msg`.
    38  func (OutputOnlyProcessor) Process(field protoreflect.FieldDescriptor, msg protoreflect.Message) (data ResultData, applied bool) {
    39  	msg.Clear(field)
    40  	return ResultData{Message: "cleared OUTPUT_ONLY field"}, true
    41  }
    42  
    43  func init() {
    44  	RegisterFieldProcessor(&OutputOnlyProcessor{}, func(field protoreflect.FieldDescriptor) ProcessAttr {
    45  		if fo := field.Options().(*descriptorpb.FieldOptions); fo != nil {
    46  			for _, fb := range proto.GetExtension(fo, annotations.E_FieldBehavior).([]annotations.FieldBehavior) {
    47  				if fb == annotations.FieldBehavior_OUTPUT_ONLY {
    48  					return ProcessIfSet
    49  				}
    50  			}
    51  		}
    52  		return ProcessNever
    53  	})
    54  }