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fieldmask.go
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fieldmask.go
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package runtime
import (
"encoding/json"
"errors"
"fmt"
"io"
"sort"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protoreflect"
field_mask "google.golang.org/protobuf/types/known/fieldmaskpb"
)
func getFieldByName(fields protoreflect.FieldDescriptors, name string) protoreflect.FieldDescriptor {
fd := fields.ByName(protoreflect.Name(name))
if fd != nil {
return fd
}
return fields.ByJSONName(name)
}
// FieldMaskFromRequestBody creates a FieldMask printing all complete paths from the JSON body.
func FieldMaskFromRequestBody(r io.Reader, msg proto.Message) (*field_mask.FieldMask, error) {
fm := &field_mask.FieldMask{}
var root interface{}
if err := json.NewDecoder(r).Decode(&root); err != nil {
if errors.Is(err, io.EOF) {
return fm, nil
}
return nil, err
}
queue := []fieldMaskPathItem{{node: root, msg: msg.ProtoReflect()}}
for len(queue) > 0 {
// dequeue an item
item := queue[0]
queue = queue[1:]
m, ok := item.node.(map[string]interface{})
switch {
case ok && len(m) > 0:
// if the item is an object, then enqueue all of its children
for k, v := range m {
if item.msg == nil {
return nil, errors.New("JSON structure did not match request type")
}
fd := getFieldByName(item.msg.Descriptor().Fields(), k)
if fd == nil {
return nil, fmt.Errorf("could not find field %q in %q", k, item.msg.Descriptor().FullName())
}
if isDynamicProtoMessage(fd.Message()) {
for _, p := range buildPathsBlindly(string(fd.FullName().Name()), v) {
newPath := p
if item.path != "" {
newPath = item.path + "." + newPath
}
queue = append(queue, fieldMaskPathItem{path: newPath})
}
continue
}
if isProtobufAnyMessage(fd.Message()) && !fd.IsList() {
_, hasTypeField := v.(map[string]interface{})["@type"]
if hasTypeField {
queue = append(queue, fieldMaskPathItem{path: k})
continue
} else {
return nil, fmt.Errorf("could not find field @type in %q in message %q", k, item.msg.Descriptor().FullName())
}
}
child := fieldMaskPathItem{
node: v,
}
if item.path == "" {
child.path = string(fd.FullName().Name())
} else {
child.path = item.path + "." + string(fd.FullName().Name())
}
switch {
case fd.IsList(), fd.IsMap():
// As per: https://github.com/protocolbuffers/protobuf/blob/master/src/google/protobuf/field_mask.proto#L85-L86
// Do not recurse into repeated fields. The repeated field goes on the end of the path and we stop.
fm.Paths = append(fm.Paths, child.path)
case fd.Message() != nil:
child.msg = item.msg.Get(fd).Message()
fallthrough
default:
queue = append(queue, child)
}
}
case ok && len(m) == 0:
fallthrough
case len(item.path) > 0:
// otherwise, it's a leaf node so print its path
fm.Paths = append(fm.Paths, item.path)
}
}
// Sort for deterministic output in the presence
// of repeated fields.
sort.Strings(fm.Paths)
return fm, nil
}
func isProtobufAnyMessage(md protoreflect.MessageDescriptor) bool {
return md != nil && (md.FullName() == "google.protobuf.Any")
}
func isDynamicProtoMessage(md protoreflect.MessageDescriptor) bool {
return md != nil && (md.FullName() == "google.protobuf.Struct" || md.FullName() == "google.protobuf.Value")
}
// buildPathsBlindly does not attempt to match proto field names to the
// json value keys. Instead it relies completely on the structure of
// the unmarshalled json contained within in.
// Returns a slice containing all subpaths with the root at the
// passed in name and json value.
func buildPathsBlindly(name string, in interface{}) []string {
m, ok := in.(map[string]interface{})
if !ok {
return []string{name}
}
var paths []string
queue := []fieldMaskPathItem{{path: name, node: m}}
for len(queue) > 0 {
cur := queue[0]
queue = queue[1:]
m, ok := cur.node.(map[string]interface{})
if !ok {
// This should never happen since we should always check that we only add
// nodes of type map[string]interface{} to the queue.
continue
}
for k, v := range m {
if mi, ok := v.(map[string]interface{}); ok {
queue = append(queue, fieldMaskPathItem{path: cur.path + "." + k, node: mi})
} else {
// This is not a struct, so there are no more levels to descend.
curPath := cur.path + "." + k
paths = append(paths, curPath)
}
}
}
return paths
}
// fieldMaskPathItem stores an in-progress deconstruction of a path for a fieldmask
type fieldMaskPathItem struct {
// the list of prior fields leading up to node connected by dots
path string
// a generic decoded json object the current item to inspect for further path extraction
node interface{}
// parent message
msg protoreflect.Message
}