94 lines
2.7 KiB
Go
94 lines
2.7 KiB
Go
package stablejson
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import (
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"bytes"
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"fmt"
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"google.golang.org/protobuf/proto"
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"google.golang.org/protobuf/reflect/protopath"
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"google.golang.org/protobuf/reflect/protorange"
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"google.golang.org/protobuf/reflect/protoreflect"
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)
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// Marshal marshals the provided message to JSON with a stable ordering based
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// on ascending field numbers.
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func Marshal(message proto.Message) ([]byte, error) {
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buf := &bytes.Buffer{}
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firstStack := []bool{true}
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err := protorange.Options{
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Stable: true,
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}.Range(message.ProtoReflect(),
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func(p protopath.Values) error {
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// Starting printing the value.
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if !firstStack[len(firstStack)-1] {
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_, _ = fmt.Fprintf(buf, ",")
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}
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firstStack[len(firstStack)-1] = false
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// Print the key.
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var fd protoreflect.FieldDescriptor
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last := p.Index(-1)
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beforeLast := p.Index(-2)
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switch last.Step.Kind() {
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case protopath.FieldAccessStep:
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fd = last.Step.FieldDescriptor()
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_, _ = fmt.Fprintf(buf, "%q:", fd.Name())
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case protopath.ListIndexStep:
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fd = beforeLast.Step.FieldDescriptor() // lists always appear in the context of a repeated field
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case protopath.MapIndexStep:
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fd = beforeLast.Step.FieldDescriptor() // maps always appear in the context of a repeated field
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_, _ = fmt.Fprintf(buf, "%v:", last.Step.MapIndex().Interface())
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case protopath.AnyExpandStep:
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_, _ = fmt.Fprintf(buf, `"@type":%q`, last.Value.Message().Descriptor().FullName())
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return nil
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case protopath.UnknownAccessStep:
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_, _ = fmt.Fprintf(buf, "?: ")
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}
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switch v := last.Value.Interface().(type) {
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case protoreflect.Message:
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_, _ = fmt.Fprintf(buf, "{")
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firstStack = append(firstStack, true)
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case protoreflect.List:
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_, _ = fmt.Fprintf(buf, "[")
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firstStack = append(firstStack, true)
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case protoreflect.Map:
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_, _ = fmt.Fprintf(buf, "{")
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firstStack = append(firstStack, true)
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case protoreflect.EnumNumber:
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var ev protoreflect.EnumValueDescriptor
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if fd != nil {
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ev = fd.Enum().Values().ByNumber(v)
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}
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if ev != nil {
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_, _ = fmt.Fprintf(buf, "%v", ev.Name())
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} else {
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_, _ = fmt.Fprintf(buf, "%v", v)
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}
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case string, []byte:
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_, _ = fmt.Fprintf(buf, "%q", v)
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default:
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_, _ = fmt.Fprintf(buf, "%v", v)
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}
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return nil
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},
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func(p protopath.Values) error {
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last := p.Index(-1)
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switch last.Value.Interface().(type) {
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case protoreflect.Message:
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if last.Step.Kind() != protopath.AnyExpandStep {
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_, _ = fmt.Fprintf(buf, "}")
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}
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case protoreflect.List:
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_, _ = fmt.Fprintf(buf, "]")
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firstStack = firstStack[:len(firstStack)-1]
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case protoreflect.Map:
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_, _ = fmt.Fprintf(buf, "}")
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firstStack = firstStack[:len(firstStack)-1]
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}
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return nil
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},
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)
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return buf.Bytes(), err
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}
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