google.golang.org/protobuf v1.36.4: proto.Clone

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify google.golang.org/protobuf/proto.Clone in pkg:golang/google.golang.org/protobuf@v1.36.4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/google.golang.org/protobuf@v1.36.4
Demonstrate these symbols/APIs:
  - google.golang.org/protobuf/proto.Clone

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:c9d6f64a4e69e885dafd5cae90c5e3ef281853c0a8b5337b91afdc8366d6908a","contract":["proto.Clone creates an isolated deep copy across nested messages, repeated lists, and map entries where mutating the clone does not affect the original","proto.Clone(nil) returns untyped nil for an untyped nil proto.Message and returns a typed nil pointer whose ProtoReflect().IsValid() is false for a typed nil pointer","proto.Clone preserves explicit field presence on proto3_optional fields set to zero values while leaving unpopulated implicit scalar fields unpopulated","proto.Clone preserves unknown wire fields on the cloned message"],"goal":"verify google.golang.org/protobuf/proto.Clone in pkg:golang/google.golang.org/protobuf@v1.36.4","kind":"HOW","packages":["pkg:golang/google.golang.org/protobuf@v1.36.4"],"schemaVersion":1,"symbols":["google.golang.org/protobuf/proto.Clone"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/google.golang.org/protobuf@v1.36.4"],"schemaVersion":1,"subject":"pkg:golang/google.golang.org/protobuf@v1.36.4","symbols":["google.golang.org/protobuf/proto.Clone"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require google.golang.org/protobuf v1.36.4

github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
google.golang.org/protobuf v1.36.4 h1:6A3ZDJHn/eNqc1i+IdefRzy/9PokBTPvcqMySR7NNIM=
google.golang.org/protobuf v1.36.4/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=

package main

import (
	"fmt"
	"os"

	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
)

func cloneTimestamp(src *timestamppb.Timestamp) *timestamppb.Timestamp {
	cloned := proto.Clone(src)
	if cloned == nil {
		return nil
	}
	return cloned.(*timestamppb.Timestamp)
}

func main() {
	orig := &timestamppb.Timestamp{Seconds: 1700000000, Nanos: 250}
	copyMsg := cloneTimestamp(orig)
	if !proto.Equal(orig, copyMsg) {
		fmt.Fprintln(os.Stderr, "cloned message does not equal original")
		os.Exit(1)
	}
	copyMsg.Seconds = 1700000099
	if orig.Seconds != 1700000000 {
		fmt.Fprintln(os.Stderr, "mutating clone affected original")
		os.Exit(1)
	}
	fmt.Printf("Verified proto.Clone: original=%d cloned=%d\n", orig.Seconds, copyMsg.Seconds)
}

{
  "schemaVersion": 1,
  "goal": "verify google.golang.org/protobuf/proto.Clone in pkg:golang/google.golang.org/protobuf@v1.36.4",
  "kind": "HOW",
  "packages": [
    "pkg:golang/google.golang.org/protobuf@v1.36.4"
  ],
  "symbols": [
    "google.golang.org/protobuf/proto.Clone"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"
	"reflect"

	"google.golang.org/protobuf/encoding/protowire"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/reflect/protodesc"
	"google.golang.org/protobuf/reflect/protoreflect"
	"google.golang.org/protobuf/reflect/protoregistry"
	"google.golang.org/protobuf/types/descriptorpb"
	"google.golang.org/protobuf/types/dynamicpb"
	"google.golang.org/protobuf/types/known/structpb"
	"google.golang.org/protobuf/types/known/timestamppb"
)

func main() {
	// Assertion 1: proto.Clone creates an isolated deep copy across nested messages, repeated lists, and map entries
	{
		orig, err := structpb.NewStruct(map[string]any{
			"name": "service-a",
			"tags": []any{"v1", "production"},
			"nested": map[string]any{
				"port": 8080,
			},
		})
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: NewStruct error: %v\n", err)
			os.Exit(1)
		}

		clonedMsg := proto.Clone(orig)
		cloned, ok := clonedMsg.(*structpb.Struct)
		if !ok {
			fmt.Fprintln(os.Stderr, "assertion 1 failed: unexpected concrete type from proto.Clone")
			os.Exit(1)
		}
		if !proto.Equal(orig, cloned) {
			fmt.Fprintln(os.Stderr, "assertion 1 failed: cloned struct does not equal original")
			os.Exit(1)
		}

		// Mutate map entry, repeated list element, and nested struct in the clone
		cloned.Fields["name"] = structpb.NewStringValue("service-b")
		cloned.Fields["tags"].GetListValue().Values[0] = structpb.NewStringValue("v2")
		cloned.Fields["nested"].GetStructValue().Fields["port"] = structpb.NewNumberValue(9090)

		if orig.Fields["name"].GetStringValue() != "service-a" {
			fmt.Fprintln(os.Stderr, "assertion 1 failed: mutating cloned map entry modified original")
			os.Exit(1)
		}
		if orig.Fields["tags"].GetListValue().Values[0].GetStringValue() != "v1" {
			fmt.Fprintln(os.Stderr, "assertion 1 failed: mutating cloned list modified original")
			os.Exit(1)
		}
		if orig.Fields["nested"].GetStructValue().Fields["port"].GetNumberValue() != 8080 {
			fmt.Fprintln(os.Stderr, "assertion 1 failed: mutating cloned nested message modified original")
			os.Exit(1)
		}
	}

	// Assertion 2: proto.Clone(nil) returns untyped nil for untyped nil and a typed nil pointer with invalid reflection for typed nil
	{
		var untypedNil proto.Message
		if got := proto.Clone(untypedNil); got != nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected untyped nil, got %v\n", got)
			os.Exit(1)
		}

		var typedNil *timestamppb.Timestamp
		gotTyped := proto.Clone(typedNil)
		if gotTyped == nil {
			fmt.Fprintln(os.Stderr, "assertion 2 failed: expected typed nil interface, got untyped nil")
			os.Exit(1)
		}
		if !reflect.ValueOf(gotTyped).IsNil() {
			fmt.Fprintln(os.Stderr, "assertion 2 failed: expected concrete value of cloned typed nil to be nil")
			os.Exit(1)
		}
		if gotTyped.ProtoReflect().IsValid() {
			fmt.Fprintln(os.Stderr, "assertion 2 failed: expected ProtoReflect().IsValid() to be false for typed nil clone")
			os.Exit(1)
		}
	}

	// Assertion 3: proto.Clone preserves explicit field presence on proto3_optional zero values while keeping unpopulated implicit fields unpopulated
	{
		fdp := &descriptorpb.FileDescriptorProto{
			Name:    proto.String("presence.proto"),
			Package: proto.String("sample.presence"),
			Syntax:  proto.String("proto3"),
			MessageType: []*descriptorpb.DescriptorProto{
				{
					Name: proto.String("Record"),
					Field: []*descriptorpb.FieldDescriptorProto{
						{
							Name:     proto.String("implicit_text"),
							Number:   proto.Int32(1),
							Type:     descriptorpb.FieldDescriptorProto_TYPE_STRING.Enum(),
							JsonName: proto.String("implicitText"),
						},
						{
							Name:           proto.String("optional_zero"),
							Number:         proto.Int32(2),
							Type:           descriptorpb.FieldDescriptorProto_TYPE_INT32.Enum(),
							JsonName:       proto.String("optionalZero"),
							Proto3Optional: proto.Bool(true),
							OneofIndex:     proto.Int32(0),
						},
					},
					OneofDecl: []*descriptorpb.OneofDescriptorProto{
						{Name: proto.String("_optional_zero")},
					},
				},
			},
		}
		fileDesc, err := protodesc.NewFile(fdp, protoregistry.GlobalFiles)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: NewFile error: %v\n", err)
			os.Exit(1)
		}
		msgDesc := fileDesc.Messages().ByName("Record")
		implicitField := msgDesc.Fields().ByName("implicit_text")
		optField := msgDesc.Fields().ByName("optional_zero")

		origDyn := dynamicpb.NewMessage(msgDesc)
		origDyn.Set(optField, protoreflect.ValueOfInt32(0))

		clonedDyn := proto.Clone(origDyn).(*dynamicpb.Message)
		if !clonedDyn.Has(optField) || clonedDyn.Get(optField).Int() != 0 {
			fmt.Fprintln(os.Stderr, "assertion 3 failed: proto.Clone lost explicit presence for proto3_optional field set to 0")
			os.Exit(1)
		}
		if clonedDyn.Has(implicitField) {
			fmt.Fprintln(os.Stderr, "assertion 3 failed: proto.Clone populated unpopulated implicit scalar field")
			os.Exit(1)
		}
	}

	// Assertion 4: proto.Clone preserves unknown wire fields on the cloned message
	{
		orig := &timestamppb.Timestamp{Seconds: 100, Nanos: 200}
		var unknownRaw []byte
		unknownRaw = protowire.AppendTag(unknownRaw, 99, protowire.VarintType)
		unknownRaw = protowire.AppendVarint(unknownRaw, 4242)
		orig.ProtoReflect().SetUnknown(protoreflect.RawFields(unknownRaw))

		cloned := proto.Clone(orig).(*timestamppb.Timestamp)
		gotUnknown := []byte(cloned.ProtoReflect().GetUnknown())
		if !bytes.Equal(gotUnknown, unknownRaw) {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: unknown fields mismatch: got %x want %x\n", gotUnknown, unknownRaw)
			os.Exit(1)
		}
	}

	fmt.Println("All proto.Clone contract assertions passed.")
}