github.com/google/go-cmp v0.5.0

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@v0.5.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/google/go-cmp@v0.5.0

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:bab791a450ccfaaeb057e8efa4f278314cc6c314c30a87d4d17fdf1d02832ca2","contract":["assert cmp.Equal panics at runtime when comparing structs with unexported fields without an explicit option","assert cmp.AllowUnexported permits comparing unexported struct fields and returns false when unexported values differ","assert combining cmp.AllowUnexported, cmp.Transformer, cmpopts.EquateEmpty, and cmpopts.SortSlices makes structs with normalized strings, reordered slices, and nil vs empty maps compare equal under cmp.Equal and return an empty diff from cmp.Diff","assert cmp.Diff returns a non-empty diff string and cmp.Equal returns false when normalized exported fields differ"],"goal":"verify pkg:golang/github.com/google/go-cmp@v0.5.0","kind":"HOW","packages":["pkg:golang/github.com/google/go-cmp@v0.5.0"],"schemaVersion":1},"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@v0.5.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/google/go-cmp@v0.5.0","verifierAdapter":"golang@1"}

module sample

go 1.21

require github.com/google/go-cmp v0.5.0

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

github.com/google/go-cmp v0.5.0 h1:/QaMHBdZ26BB3SSst0Iwl10Epc+xhTquomWX0oZEB6w=
github.com/google/go-cmp v0.5.0/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@v0.5.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.5.0"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

type item struct {
	Name   string
	Labels []string
	Attrs  map[string]int
	note   string
}

func didPanic(fn func()) (panicked bool) {
	defer func() {
		if recover() != nil {
			panicked = true
		}
	}()
	fn()
	return false
}

func main() {
	left := item{
		Name:   "Widget",
		Labels: []string{"b", "a"},
		Attrs:  nil,
		note:   "hidden-1",
	}
	right := item{
		Name:   " widget ",
		Labels: []string{"a", "b"},
		Attrs:  map[string]int{},
		note:   "hidden-1",
	}

	// 1. cmp.Equal panics when comparing structs with unexported fields and no option handling them.
	if !didPanic(func() { cmp.Equal(left, right) }) {
		fmt.Fprintln(os.Stderr, "expected panic on unexported field without options")
		os.Exit(1)
	}

	// 2. cmp.AllowUnexported permits comparing unexported fields; differing unexported values return false.
	diffNote := right
	diffNote.Name = left.Name
	diffNote.Labels = left.Labels
	diffNote.Attrs = left.Attrs
	diffNote.note = "hidden-2"
	if cmp.Equal(left, diffNote, cmp.AllowUnexported(item{})) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal to return false when unexported field differs")
		os.Exit(1)
	}

	// 3. Combining cmp.AllowUnexported, cmp.Transformer, cmpopts.EquateEmpty, and cmpopts.SortSlices makes left and right equal and cmp.Diff empty.
	normStr := cmp.Transformer("TrimLower", func(s string) string {
		return strings.ToLower(strings.TrimSpace(s))
	})
	opts := cmp.Options{
		cmp.AllowUnexported(item{}),
		normStr,
		cmpopts.EquateEmpty(),
		cmpopts.SortSlices(func(a, b string) bool { return a < b }),
	}
	if !cmp.Equal(left, right, opts) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal to return true with combined options")
		os.Exit(1)
	}
	if diff := cmp.Diff(left, right, opts); diff != "" {
		fmt.Fprintf(os.Stderr, "expected empty diff, got:\n%s\n", diff)
		os.Exit(1)
	}

	// 4. cmp.Diff reports a non-empty diff when an exported field differs even after normalization.
	mismatch := right
	mismatch.Name = "Gadget"
	if cmp.Equal(left, mismatch, opts) {
		fmt.Fprintln(os.Stderr, "expected cmp.Equal to return false for mismatched Name")
		os.Exit(1)
	}
	if diff := cmp.Diff(left, mismatch, opts); diff == "" {
		fmt.Fprintln(os.Stderr, "expected non-empty diff for mismatched Name")
		os.Exit(1)
	}
}