google.golang.org/protobuf v1.35.1: proto.Marshal

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.Marshal in pkg:golang/google.golang.org/protobuf@v1.35.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/google.golang.org/protobuf@v1.35.1
Demonstrate these symbols/APIs:
  - google.golang.org/protobuf/proto.Marshal
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: esm
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:963f3cbc506971cf17eafd8fde9309a95e7d7fed178c0b942f8ff187d6d96745","contract":["proto.Marshal serializes a proto.Message into wire-format bytes and roundtrips with proto.Unmarshal","proto.Marshal produces standard protobuf length-delimited wire encoding for StringValue","proto.Marshal serializes an empty protobuf message into zero bytes","proto.MarshalOptions.Deterministic produces reproducible binary output","proto.MarshalOptions.MarshalAppend appends encoded message to an existing byte buffer","proto.Size returns the exact byte length produced by proto.Marshal","proto.Marshal on nil proto.Message returns empty bytes without error"],"goal":"verify google.golang.org/protobuf/proto.Marshal in pkg:golang/google.golang.org/protobuf@v1.35.1","kind":"HOW","packages":["pkg:golang/google.golang.org/protobuf@v1.35.1"],"schemaVersion":1,"symbols":["google.golang.org/protobuf/proto.Marshal"]},"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@v1.35.1"],"schemaVersion":1,"subject":"pkg:golang/google.golang.org/protobuf@v1.35.1","symbols":["google.golang.org/protobuf/proto.Marshal"],"verifierAdapter":"golang@1"}

module sample-protobuf-marshal

go 1.23.0

require google.golang.org/protobuf v1.35.1

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 v1.35.1 h1:m3LfL6/Ca+fqnjnlqQXNpFPABW1UD7mjh8KO2mKFytA=
google.golang.org/protobuf v1.35.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=

package main

import (
	"fmt"
	"time"

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

func main() {
	// 1. Marshal a string wrapper message
	msg := wrapperspb.String("Hello, Protobuf!")
	data, err := proto.Marshal(msg)
	if err != nil {
		fmt.Printf("marshal error: %v\n", err)
		return
	}
	fmt.Printf("Marshaled string wrapper (%d bytes): %x\n", len(data), data)

	// Unmarshal back to verify roundtrip
	var unmarshaled wrapperspb.StringValue
	if err := proto.Unmarshal(data, &unmarshaled); err != nil {
		fmt.Printf("unmarshal error: %v\n", err)
		return
	}
	fmt.Printf("Unmarshaled value: %s\n", unmarshaled.GetValue())

	// 2. Marshal a Timestamp message
	ts := timestamppb.New(time.Date(2026, 8, 27, 10, 0, 0, 0, time.UTC))
	tsData, err := proto.Marshal(ts)
	if err != nil {
		fmt.Printf("timestamp marshal error: %v\n", err)
		return
	}
	fmt.Printf("Marshaled timestamp (%d bytes)\n", len(tsData))

	// 3. Marshal a dynamic structpb message
	st, err := structpb.NewStruct(map[string]any{
		"name":   "CodeSampleX",
		"active": true,
		"count":  42,
	})
	if err != nil {
		fmt.Printf("structpb creation error: %v\n", err)
		return
	}
	stData, err := proto.Marshal(st)
	if err != nil {
		fmt.Printf("structpb marshal error: %v\n", err)
		return
	}
	fmt.Printf("Marshaled structpb (%d bytes)\n", len(stData))
}

{
  "schemaVersion": 1,
  "goal": "verify google.golang.org/protobuf/proto.Marshal in pkg:golang/google.golang.org/protobuf@v1.35.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/google.golang.org/protobuf@v1.35.1"
  ],
  "symbols": [
    "google.golang.org/protobuf/proto.Marshal"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "esm",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"bytes"
	"fmt"
	"os"

	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/emptypb"
	"google.golang.org/protobuf/types/known/structpb"
	"google.golang.org/protobuf/types/known/wrapperspb"
)

func main() {
	// Assertion 1: proto.Marshal serializes a proto.Message into wire-format bytes and roundtrips with proto.Unmarshal
	{
		msg := wrapperspb.String("test-payload")
		data, err := proto.Marshal(msg)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Marshal failed: %v\n", err)
			os.Exit(1)
		}
		if len(data) == 0 {
			fmt.Fprintln(os.Stderr, "FAIL: proto.Marshal produced empty output for non-empty message")
			os.Exit(1)
		}

		var restored wrapperspb.StringValue
		if err := proto.Unmarshal(data, &restored); err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Unmarshal failed: %v\n", err)
			os.Exit(1)
		}
		if !proto.Equal(msg, &restored) {
			fmt.Fprintf(os.Stderr, "FAIL: restored message not equal to original: got %v, want %v\n", &restored, msg)
			os.Exit(1)
		}
	}

	// Assertion 2: proto.Marshal produces standard protobuf length-delimited wire encoding for StringValue
	{
		msg := wrapperspb.String("hello")
		data, err := proto.Marshal(msg)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Marshal failed: %v\n", err)
			os.Exit(1)
		}
		// StringValue field 1 (tag 1, wire type 2 -> 0x0a), length 5 (0x05), bytes "hello" (0x68, 0x65, 0x6c, 0x6c, 0x6f)
		expected := []byte{0x0a, 0x05, 'h', 'e', 'l', 'l', 'o'}
		if !bytes.Equal(data, expected) {
			fmt.Fprintf(os.Stderr, "FAIL: wire format mismatch: got %x, want %x\n", data, expected)
			os.Exit(1)
		}
	}

	// Assertion 3: proto.Marshal serializes an empty protobuf message into zero bytes
	{
		empty := &emptypb.Empty{}
		data, err := proto.Marshal(empty)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Marshal on empty message failed: %v\n", err)
			os.Exit(1)
		}
		if len(data) != 0 {
			fmt.Fprintf(os.Stderr, "FAIL: expected 0 bytes for Empty message, got %d bytes\n", len(data))
			os.Exit(1)
		}
	}

	// Assertion 4: proto.MarshalOptions.Deterministic produces reproducible binary output
	{
		st, err := structpb.NewStruct(map[string]any{
			"zebra":  1,
			"apple":  2,
			"mango":  3,
			"banana": 4,
		})
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: structpb.NewStruct failed: %v\n", err)
			os.Exit(1)
		}

		opts := proto.MarshalOptions{Deterministic: true}
		data1, err1 := opts.Marshal(st)
		data2, err2 := opts.Marshal(st)
		if err1 != nil || err2 != nil {
			fmt.Fprintf(os.Stderr, "FAIL: deterministic marshal failed: err1=%v, err2=%v\n", err1, err2)
			os.Exit(1)
		}
		if !bytes.Equal(data1, data2) {
			fmt.Fprintln(os.Stderr, "FAIL: Deterministic marshal produced different outputs for same message")
			os.Exit(1)
		}
	}

	// Assertion 5: proto.MarshalOptions.MarshalAppend appends encoded message to an existing byte buffer
	{
		prefix := []byte("HEADER:")
		msg := wrapperspb.Int32(999)
		opts := proto.MarshalOptions{}

		appended, err := opts.MarshalAppend(prefix, msg)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: MarshalAppend failed: %v\n", err)
			os.Exit(1)
		}
		if !bytes.HasPrefix(appended, prefix) {
			fmt.Fprintln(os.Stderr, "FAIL: MarshalAppend did not preserve prefix buffer")
			os.Exit(1)
		}
		expectedBody, _ := proto.Marshal(msg)
		if !bytes.Equal(appended[len(prefix):], expectedBody) {
			fmt.Fprintln(os.Stderr, "FAIL: MarshalAppend appended payload mismatch")
			os.Exit(1)
		}
	}

	// Assertion 6: proto.Size returns the exact byte length produced by proto.Marshal
	{
		msg := wrapperspb.String("size-verification-string-12345")
		data, err := proto.Marshal(msg)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Marshal failed: %v\n", err)
			os.Exit(1)
		}
		size := proto.Size(msg)
		if size != len(data) {
			fmt.Fprintf(os.Stderr, "FAIL: proto.Size mismatch: got %d, wire len %d\n", size, len(data))
			os.Exit(1)
		}
	}

	// Assertion 7: proto.Marshal on nil proto.Message returns empty bytes without error
	{
		data, err := proto.Marshal(nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: expected nil error for nil message, got %v\n", err)
			os.Exit(1)
		}
		if len(data) != 0 {
			fmt.Fprintf(os.Stderr, "FAIL: expected 0 bytes for nil message, got %d bytes\n", len(data))
			os.Exit(1)
		}
	}

	fmt.Println("PASS: google.golang.org/protobuf/proto.Marshal contract passed")
}