github.com/google/go-cmp v0.5.1: cmp.Diff, cmp.Equal, cmpopts.EquateEmpty

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@v0.5.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/google/go-cmp@v0.5.1

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:sha256:325a166f7ee7232100de3fc80a7f9a01228e79d7ab8c83867748621aa19aba87","contract":["assert cmp.Equal panics at runtime when comparing structs containing unexported fields without an explicit option","assert cmpopts.IgnoreUnexported prevents unexported field panics while preserving inequality on unordered slices and nil vs empty maps","assert combining cmpopts.IgnoreUnexported, cmpopts.EquateEmpty, and cmpopts.SortSlices makes structs with reordered slices and nil vs empty maps compare equal under cmp.Equal and return an empty string from cmp.Diff","assert cmp.Diff returns a non-empty diff string and cmp.Equal returns false when exported fields genuinely differ under those options"],"goal":"verify pkg:golang/github.com/google/go-cmp@v0.5.1","kind":"HOW","packages":["pkg:golang/github.com/google/go-cmp@v0.5.1"],"schemaVersion":1,"symbols":["cmp.Diff","cmp.Equal","cmpopts.EquateEmpty","cmpopts.IgnoreUnexported","cmpopts.SortSlices"]},"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@v0.5.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/google/go-cmp@v0.5.1","symbols":["cmp.Diff","cmp.Equal","cmpopts.EquateEmpty","cmpopts.IgnoreUnexported","cmpopts.SortSlices"],"verifierAdapter":"golang@1"}

module sample

go 1.21

require github.com/google/go-cmp v0.5.1

require golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 // indirect

github.com/google/go-cmp v0.5.1 h1:JFrFEBb2xKufg6XkJsJr+WbKb4FQlURi5RUcBveYu9k=
github.com/google/go-cmp v0.5.1/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=

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/google/go-cmp@v0.5.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.5.1"
  ]
}

package main

import (
	"fmt"
	"os"

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

type record struct {
	ID       int
	Tags     []string
	Metadata map[string]string
	internal string
}

func panics(fn func()) (panicked bool) {
	defer func() {
		if r := recover(); r != nil {
			panicked = true
		}
	}()
	fn()
	return false
}

func main() {
	a := record{
		ID:       10,
		Tags:     []string{"beta", "alpha"},
		Metadata: nil,
		internal: "secret-a",
	}
	b := record{
		ID:       10,
		Tags:     []string{"alpha", "beta"},
		Metadata: map[string]string{},
		internal: "secret-b",
	}

	// 1. Comparing structs with unexported fields without an option panics at runtime.
	if !panics(func() { cmp.Equal(a, b) }) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal without IgnoreUnexported to panic on unexported fields")
		os.Exit(1)
	}

	// 2. With IgnoreUnexported alone, nil vs empty map and unordered slices still differ.
	ignoreOpt := cmpopts.IgnoreUnexported(record{})
	if cmp.Equal(a, b, ignoreOpt) {
		fmt.Fprintln(os.Stderr, "expected unequal when slices are unordered and map is nil vs empty")
		os.Exit(1)
	}

	// 3. Combining IgnoreUnexported, EquateEmpty, and SortSlices makes them compare equal and produces an empty diff.
	opts := cmp.Options{
		ignoreOpt,
		cmpopts.EquateEmpty(),
		cmpopts.SortSlices(func(x, y string) bool { return x < y }),
	}
	if !cmp.Equal(a, b, opts) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal to return true with combined options")
		os.Exit(1)
	}
	if diff := cmp.Diff(a, b, opts); diff != "" {
		fmt.Fprintf(os.Stderr, "expected empty diff, got:\n%s\n", diff)
		os.Exit(1)
	}

	// 4. When exported fields genuinely differ, cmp.Diff returns a non-empty diff.
	c := b
	c.ID = 20
	if cmp.Equal(a, c, opts) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal to return false when ID differs")
		os.Exit(1)
	}
	if diff := cmp.Diff(a, c, opts); diff == "" {
		fmt.Fprintln(os.Stderr, "expected non-empty diff when ID differs")
		os.Exit(1)
	}
}