github.com/google/go-cmp v0.5.1: cmp.Equal

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 github.com/google/go-cmp/cmp.Equal in 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
Demonstrate these symbols/APIs:
  - github.com/google/go-cmp/cmp.Equal

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:sha256:284f46d4569fef23d0919baa19802d095a03078cf995149e7da0f630e9ab6ed3","contract":["cmp.Equal returns true for identical primitive, slice, and map values and false for differences","cmp.Equal returns true for identical structs with exported fields and false for struct field differences","cmp.Equal supports cmp.Comparer for custom equality predicates","cmpopts.IgnoreFields excludes specified struct fields from comparison in cmp.Equal","cmpopts.SortSlices compares unordered slices in cmp.Equal","cmpopts.IgnoreUnexported and cmp.AllowUnexported handle structs with unexported fields in cmp.Equal","cmp.Transformer applies value transformations before comparison in cmp.Equal","cmpopts.EquateEmpty treats nil and empty slices or maps as equal in cmp.Equal"],"goal":"verify github.com/google/go-cmp/cmp.Equal in 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":["github.com/google/go-cmp/cmp.Equal"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","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":["github.com/google/go-cmp/cmp.Equal"],"verifierAdapter":"golang@1"}

module sample

go 1.22

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 github.com/google/go-cmp/cmp.Equal in pkg:golang/github.com/google/go-cmp@v0.5.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.5.1"
  ],
  "symbols": [
    "github.com/google/go-cmp/cmp.Equal"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

type itemRecord struct {
	ID       int
	Category string
	Revision string
}

type stateHolder struct {
	Label  string
	hidden string
}

func main() {
	if err := verifyCmpEqual(); err != nil {
		fmt.Fprintf(os.Stderr, "contract failure: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("contract verified")
}

func verifyCmpEqual() error {
	// 1. Primitive, slice, and map equality
	if !cmp.Equal(100, 100) {
		return fmt.Errorf("expected equal integers to return true")
	}
	if cmp.Equal(100, 101) {
		return fmt.Errorf("expected distinct integers to return false")
	}
	if !cmp.Equal([]string{"one", "two"}, []string{"one", "two"}) {
		return fmt.Errorf("expected identical slices to return true")
	}
	if cmp.Equal([]string{"one", "two"}, []string{"two", "one"}) {
		return fmt.Errorf("expected differently ordered slices to return false")
	}
	if !cmp.Equal(map[string]int{"k1": 10, "k2": 20}, map[string]int{"k2": 20, "k1": 10}) {
		return fmt.Errorf("expected identical maps to return true")
	}

	// 2. Structs with exported fields
	r1 := itemRecord{ID: 7, Category: "books", Revision: "v1"}
	r2 := itemRecord{ID: 7, Category: "books", Revision: "v1"}
	r3 := itemRecord{ID: 7, Category: "music", Revision: "v1"}
	if !cmp.Equal(r1, r2) {
		return fmt.Errorf("expected identical structs to return true")
	}
	if cmp.Equal(r1, r3) {
		return fmt.Errorf("expected differing structs to return false")
	}

	// 3. Custom equality via cmp.Comparer
	floatTolerance := cmp.Comparer(func(a, b float64) bool {
		diff := a - b
		if diff < 0 {
			diff = -diff
		}
		return diff < 1e-3
	})
	if !cmp.Equal(3.1415, 3.1419, floatTolerance) {
		return fmt.Errorf("expected floats within tolerance to be equal")
	}
	if cmp.Equal(3.14, 3.20, floatTolerance) {
		return fmt.Errorf("expected floats outside tolerance to be unequal")
	}

	// 4. Ignoring specific struct fields with cmpopts.IgnoreFields
	r4 := itemRecord{ID: 9, Category: "tools", Revision: "v1"}
	r5 := itemRecord{ID: 9, Category: "tools", Revision: "v2"}
	if cmp.Equal(r4, r5) {
		return fmt.Errorf("expected structs with different Revision to be unequal by default")
	}
	if !cmp.Equal(r4, r5, cmpopts.IgnoreFields(itemRecord{}, "Revision")) {
		return fmt.Errorf("expected IgnoreFields to ignore Revision field")
	}

	// 5. Order-independent slice comparison with cmpopts.SortSlices
	numsA := []int{9, 3, 7, 1}
	numsB := []int{1, 3, 7, 9}
	less := func(x, y int) bool { return x < y }
	if cmp.Equal(numsA, numsB) {
		return fmt.Errorf("expected unsorted slices to be unequal without SortSlices")
	}
	if !cmp.Equal(numsA, numsB, cmpopts.SortSlices(less)) {
		return fmt.Errorf("expected SortSlices to equate unordered slices")
	}

	// 6. Handling unexported struct fields with cmpopts.IgnoreUnexported and cmp.AllowUnexported
	s1 := stateHolder{Label: "active", hidden: "alpha"}
	s2 := stateHolder{Label: "active", hidden: "beta"}
	if !cmp.Equal(s1, s2, cmpopts.IgnoreUnexported(stateHolder{})) {
		return fmt.Errorf("expected IgnoreUnexported to ignore unexported fields")
	}
	s3 := stateHolder{Label: "active", hidden: "alpha"}
	if !cmp.Equal(s1, s3, cmp.AllowUnexported(stateHolder{})) {
		return fmt.Errorf("expected AllowUnexported to compare matching unexported fields")
	}
	if cmp.Equal(s1, s2, cmp.AllowUnexported(stateHolder{})) {
		return fmt.Errorf("expected AllowUnexported to detect differing unexported fields")
	}

	// 7. Value transformation with cmp.Transformer
	normalizeCase := cmp.Transformer("Lower", strings.ToLower)
	if !cmp.Equal("GoCmpEqual", "gocmpequal", normalizeCase) {
		return fmt.Errorf("expected Transformer to normalize case before comparison")
	}

	// 8. Equating nil and empty slices/maps with cmpopts.EquateEmpty
	var nilSlice []int
	emptySlice := []int{}
	if cmp.Equal(nilSlice, emptySlice) {
		return fmt.Errorf("expected nil and empty slice to be unequal by default")
	}
	if !cmp.Equal(nilSlice, emptySlice, cmpopts.EquateEmpty()) {
		return fmt.Errorf("expected EquateEmpty to equate nil and empty slice")
	}

	return nil
}