discard.go

Documentation: github.com/golang/protobuf/proto

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package proto
     6  
     7  import (
     8  	"google.golang.org/protobuf/reflect/protoreflect"
     9  )
    10  
    11  // DiscardUnknown recursively discards all unknown fields from this message
    12  // and all embedded messages.
    13  //
    14  // When unmarshaling a message with unrecognized fields, the tags and values
    15  // of such fields are preserved in the Message. This allows a later call to
    16  // marshal to be able to produce a message that continues to have those
    17  // unrecognized fields. To avoid this, DiscardUnknown is used to
    18  // explicitly clear the unknown fields after unmarshaling.
    19  func DiscardUnknown(m Message) {
    20  	if m != nil {
    21  		discardUnknown(MessageReflect(m))
    22  	}
    23  }
    24  
    25  func discardUnknown(m protoreflect.Message) {
    26  	m.Range(func(fd protoreflect.FieldDescriptor, val protoreflect.Value) bool {
    27  		switch {
    28  		// Handle singular message.
    29  		case fd.Cardinality() != protoreflect.Repeated:
    30  			if fd.Message() != nil {
    31  				discardUnknown(m.Get(fd).Message())
    32  			}
    33  		// Handle list of messages.
    34  		case fd.IsList():
    35  			if fd.Message() != nil {
    36  				ls := m.Get(fd).List()
    37  				for i := 0; i < ls.Len(); i++ {
    38  					discardUnknown(ls.Get(i).Message())
    39  				}
    40  			}
    41  		// Handle map of messages.
    42  		case fd.IsMap():
    43  			if fd.MapValue().Message() != nil {
    44  				ms := m.Get(fd).Map()
    45  				ms.Range(func(_ protoreflect.MapKey, v protoreflect.Value) bool {
    46  					discardUnknown(v.Message())
    47  					return true
    48  				})
    49  			}
    50  		}
    51  		return true
    52  	})
    53  
    54  	// Discard unknown fields.
    55  	if len(m.GetUnknown()) > 0 {
    56  		m.SetUnknown(nil)
    57  	}
    58  }
    59
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