update.go

Documentation: go.einride.tech/aip/fieldmask

     1  package fieldmask
     2  
     3  import (
     4  	"fmt"
     5  	"strings"
     6  
     7  	"google.golang.org/protobuf/proto"
     8  	"google.golang.org/protobuf/reflect/protoreflect"
     9  	"google.golang.org/protobuf/types/known/fieldmaskpb"
    10  )
    11  
    12  // Update updates fields in dst with values from src according to the provided field mask.
    13  // Nested messages are recursively updated in the same manner.
    14  // Repeated fields and maps are copied by reference from src to dst.
    15  // Field mask paths referring to Individual entries in maps or
    16  // repeated fields are ignored.
    17  //
    18  // If no update mask is provided, only non-zero values of src are copied to dst.
    19  // If the special value "*" is provided as the field mask, a full replacement of all fields in dst is done.
    20  //
    21  // See: https://google.aip.dev/134 (Standard methods: Update).
    22  func Update(mask *fieldmaskpb.FieldMask, dst, src proto.Message) {
    23  	dstReflect := dst.ProtoReflect()
    24  	srcReflect := src.ProtoReflect()
    25  	if dstReflect.Descriptor() != srcReflect.Descriptor() {
    26  		panic(fmt.Sprintf(
    27  			"dst (%s) and src (%s) messages have different types",
    28  			dstReflect.Descriptor().FullName(),
    29  			srcReflect.Descriptor().FullName(),
    30  		))
    31  	}
    32  	switch {
    33  	// Special-case: No update mask.
    34  	// Update all fields of src that are set on the wire.
    35  	case len(mask.GetPaths()) == 0:
    36  		updateWireSetFields(dstReflect, srcReflect)
    37  	// Special-case: Update mask is [*].
    38  	// Do a full replacement of all fields.
    39  	case IsFullReplacement(mask):
    40  		proto.Reset(dst)
    41  		proto.Merge(dst, src)
    42  	default:
    43  		for _, path := range mask.GetPaths() {
    44  			segments := strings.Split(path, ".")
    45  			updateNamedField(dstReflect, srcReflect, segments)
    46  		}
    47  	}
    48  }
    49  
    50  func updateWireSetFields(dst, src protoreflect.Message) {
    51  	src.Range(func(field protoreflect.FieldDescriptor, value protoreflect.Value) bool {
    52  		switch {
    53  		case field.IsList():
    54  			dst.Set(field, value)
    55  		case field.IsMap():
    56  			dst.Set(field, value)
    57  		case field.Message() != nil && !dst.Has(field):
    58  			dst.Set(field, value)
    59  		case field.Message() != nil:
    60  			updateWireSetFields(dst.Get(field).Message(), value.Message())
    61  		default:
    62  			dst.Set(field, value)
    63  		}
    64  		return true
    65  	})
    66  }
    67  
    68  func updateNamedField(dst, src protoreflect.Message, segments []string) {
    69  	if len(segments) == 0 {
    70  		return
    71  	}
    72  	field := src.Descriptor().Fields().ByName(protoreflect.Name(segments[0]))
    73  	if field == nil {
    74  		// no known field by that name
    75  		return
    76  	}
    77  	// a named field in this message
    78  	if len(segments) == 1 {
    79  		if !src.Has(field) {
    80  			dst.Clear(field)
    81  		} else {
    82  			dst.Set(field, src.Get(field))
    83  		}
    84  		return
    85  	}
    86  
    87  	// a named field in a nested message
    88  	switch {
    89  	case field.IsList(), field.IsMap():
    90  		// nested fields in repeated or map not supported
    91  		return
    92  	case field.Message() != nil:
    93  		// if message field is not set, allocate an empty value
    94  		if !dst.Has(field) {
    95  			dst.Set(field, dst.NewField(field))
    96  		}
    97  		if !src.Has(field) {
    98  			src.Set(field, src.NewField(field))
    99  		}
   100  		updateNamedField(dst.Get(field).Message(), src.Get(field).Message(), segments[1:])
   101  	default:
   102  		return
   103  	}
   104  }
   105
View as plain text