google.golang.org/protobuf v1.36.4: 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@v1.36.4
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.Marshal

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:sha256:1da99177f545ef8c7187f034a8014541de4ec68c2e2b65f46490b322099ae1a3","contract":["proto.Marshal serializes wrapperspb.String(\"hello\") to wire bytes 0x0a0568656c6c6f without error","proto.Unmarshal round-trips the marshaled wire bytes back to a wrapperspb.StringValue with Value == \"hello\"","proto.Marshal on an empty wrapperspb.StringValue returns an empty byte slice without error"],"goal":"verify google.golang.org/protobuf/proto.Marshal 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.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@v1.36.4"],"schemaVersion":1,"subject":"pkg:golang/google.golang.org/protobuf@v1.36.4","symbols":["google.golang.org/protobuf/proto.Marshal"],"verifierAdapter":"golang@1"}

module sample

go 1.21

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=

{
  "schemaVersion": 1,
  "goal": "verify google.golang.org/protobuf/proto.Marshal 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.Marshal"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"

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

func main() {
	msg := wrapperspb.String("hello")
	data, err := proto.Marshal(msg)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Marshal error: %v\n", err)
		os.Exit(1)
	}
	expected := []byte{0x0a, 0x05, 'h', 'e', 'l', 'l', 'o'}
	if !bytes.Equal(data, expected) {
		fmt.Fprintf(os.Stderr, "unexpected wire bytes: got %x, want %x\n", data, expected)
		os.Exit(1)
	}

	var decoded wrapperspb.StringValue
	if err := proto.Unmarshal(data, &decoded); err != nil {
		fmt.Fprintf(os.Stderr, "Unmarshal error: %v\n", err)
		os.Exit(1)
	}
	if decoded.Value != "hello" {
		fmt.Fprintf(os.Stderr, "unexpected decoded value: got %q, want %q\n", decoded.Value, "hello")
		os.Exit(1)
	}

	emptyData, err := proto.Marshal(&wrapperspb.StringValue{})
	if err != nil {
		fmt.Fprintf(os.Stderr, "Marshal empty error: %v\n", err)
		os.Exit(1)
	}
	if len(emptyData) != 0 {
		fmt.Fprintf(os.Stderr, "expected empty bytes for default message, got %x\n", emptyData)
		os.Exit(1)
	}
}