github.com/google/go-cmp v0.3.0: cmp.Equal, cmp.Diff, cmp.AllowUnexported

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 pkg:golang/github.com/google/go-cmp@v0.3.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/google/go-cmp@v0.3.0

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:sha256:23e39b57df8ffb72197eb90a35b748ba03cfdd2797ed85907b5ddb902461306e","contract":["assert cmp.Equal returns true and cmp.Diff returns empty string when only ignored fields differ","assert cmp.Equal returns false and cmp.Diff names the differing field when non-ignored fields differ","assert cmp.Equal panics on structs with unexported fields when cmp.AllowUnexported is omitted"],"goal":"verify pkg:golang/github.com/google/go-cmp@v0.3.0","kind":"HOW","packages":["pkg:golang/github.com/google/go-cmp@v0.3.0"],"schemaVersion":1,"symbols":["cmp.Equal","cmp.Diff","cmp.AllowUnexported","cmpopts.IgnoreFields"]},"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/github.com/google/go-cmp@v0.3.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/google/go-cmp@v0.3.0","symbols":["cmp.Equal","cmp.Diff","cmp.AllowUnexported","cmpopts.IgnoreFields"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.21

require github.com/google/go-cmp v0.3.0

github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/google/go-cmp@v0.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.3.0"
  ]
}

package sample

import (
	"github.com/google/go-cmp/cmp"
	"github.com/google/go-cmp/cmp/cmpopts"
)

type Config struct {
	Host     string
	Port     int
	Revision string
	secret   string
}

func NewConfig(host string, port int, revision, secret string) Config {
	return Config{
		Host:     host,
		Port:     port,
		Revision: revision,
		secret:   secret,
	}
}

func EqualIgnoringRevision(a, b Config) bool {
	return cmp.Equal(a, b,
		cmp.AllowUnexported(Config{}),
		cmpopts.IgnoreFields(Config{}, "Revision"),
	)
}

func DiffIgnoringRevision(a, b Config) string {
	return cmp.Diff(a, b,
		cmp.AllowUnexported(Config{}),
		cmpopts.IgnoreFields(Config{}, "Revision"),
	)
}

func EqualDefaultPanics(a, b Config) (panicked bool) {
	defer func() {
		if recover() != nil {
			panicked = true
		}
	}()
	_ = cmp.Equal(a, b)
	return false
}

package main

import (
	"fmt"
	"os"
	"strings"

	sample "example.com/sample/src"
)

func fail(msg string) {
	fmt.Fprintln(os.Stderr, msg)
	os.Exit(1)
}

func main() {
	c1 := sample.NewConfig("localhost", 8080, "rev-1", "k1")
	c2 := sample.NewConfig("localhost", 8080, "rev-2", "k1")
	c3 := sample.NewConfig("localhost", 9090, "rev-1", "k1")

	if !sample.EqualIgnoringRevision(c1, c2) {
		fail("expected configs differing only in ignored Revision field to be equal")
	}

	if d := sample.DiffIgnoringRevision(c1, c2); d != "" {
		fail("expected empty diff when only ignored Revision field differs")
	}

	if sample.EqualIgnoringRevision(c1, c3) {
		fail("expected configs with different Port to be unequal")
	}

	diff := sample.DiffIgnoringRevision(c1, c3)
	if diff == "" || !strings.Contains(diff, "Port") {
		fail("expected non-empty diff mentioning Port")
	}

	if !sample.EqualDefaultPanics(c1, c2) {
		fail("expected cmp.Equal without AllowUnexported to panic on unexported struct field")
	}

	fmt.Println("ok")
}