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

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/google/go-cmp@v0.3.0
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:sha256:59e7fd3c1c1fe65eba6af4476e312c4e55eb03708514df0853ad8a0242c86594","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.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@v0.3.0","kind":"HOW","packages":["pkg:golang/github.com/google/go-cmp@v0.3.0"],"schemaVersion":1,"symbols":["github.com/google/go-cmp/cmp.Equal"]},"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":["github.com/google/go-cmp/cmp.Equal"],"verifierAdapter":"golang@1"}

module sample

go 1.22

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 github.com/google/go-cmp/cmp.Equal in pkg:golang/github.com/google/go-cmp@v0.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.3.0"
  ],
  "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
	Label    string
	Category string
}

type boxState struct {
	Code     string
	internal int
}

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

func runContract() error {
	// 1. cmp.Equal returns true for identical primitive, slice, and map values and false for differences
	if !cmp.Equal(100, 100) {
		return fmt.Errorf("expected 100 == 100")
	}
	if cmp.Equal(100, 200) {
		return fmt.Errorf("expected 100 != 200")
	}
	if !cmp.Equal([]int{1, 2, 3}, []int{1, 2, 3}) {
		return fmt.Errorf("expected identical int slices to be equal")
	}
	if cmp.Equal([]int{1, 2, 3}, []int{1, 3, 2}) {
		return fmt.Errorf("expected reordered int slices to be unequal by default")
	}
	if !cmp.Equal(map[string]int{"x": 10, "y": 20}, map[string]int{"y": 20, "x": 10}) {
		return fmt.Errorf("expected identical maps to be equal")
	}

	// 2. cmp.Equal returns true for identical structs with exported fields and false for struct field differences
	r1 := itemRecord{ID: 1, Label: "unit-a", Category: "group-1"}
	r2 := itemRecord{ID: 1, Label: "unit-a", Category: "group-1"}
	r3 := itemRecord{ID: 1, Label: "unit-b", Category: "group-1"}
	if !cmp.Equal(r1, r2) {
		return fmt.Errorf("expected identical structs to be equal")
	}
	if cmp.Equal(r1, r3) {
		return fmt.Errorf("expected differing structs to be unequal")
	}

	// 3. cmp.Equal supports cmp.Comparer for custom equality predicates
	closeFloat := cmp.Comparer(func(a, b float64) bool {
		diff := a - b
		if diff < 0 {
			diff = -diff
		}
		return diff < 1e-4
	})
	if !cmp.Equal(10.00001, 10.00002, closeFloat) {
		return fmt.Errorf("expected custom comparer to match within tolerance")
	}
	if cmp.Equal(10.0, 10.5, closeFloat) {
		return fmt.Errorf("expected custom comparer to reject values outside tolerance")
	}

	// 4. cmpopts.IgnoreFields excludes specified struct fields from comparison in cmp.Equal
	r4 := itemRecord{ID: 5, Label: "unit-c", Category: "cat-a"}
	r5 := itemRecord{ID: 5, Label: "unit-c", Category: "cat-b"}
	if cmp.Equal(r4, r5) {
		return fmt.Errorf("expected structs with different Category to differ without options")
	}
	if !cmp.Equal(r4, r5, cmpopts.IgnoreFields(itemRecord{}, "Category")) {
		return fmt.Errorf("expected IgnoreFields to ignore Category field")
	}

	// 5. cmpopts.IgnoreUnexported and cmp.AllowUnexported handle structs with unexported fields in cmp.Equal
	b1 := boxState{Code: "s1", internal: 10}
	b2 := boxState{Code: "s1", internal: 20}
	if !cmp.Equal(b1, b2, cmpopts.IgnoreUnexported(boxState{})) {
		return fmt.Errorf("expected IgnoreUnexported to ignore unexported fields")
	}
	b3 := boxState{Code: "s1", internal: 10}
	if !cmp.Equal(b1, b3, cmp.AllowUnexported(boxState{})) {
		return fmt.Errorf("expected AllowUnexported to compare equal unexported fields")
	}
	if cmp.Equal(b1, b2, cmp.AllowUnexported(boxState{})) {
		return fmt.Errorf("expected AllowUnexported to detect differing unexported fields")
	}

	// 6. cmp.Transformer applies value transformations before comparison in cmp.Equal
	trimAndLower := cmp.Transformer("NormalizeString", func(s string) string {
		return strings.ToLower(strings.TrimSpace(s))
	})
	if !cmp.Equal("   SampleValue ", "samplevalue", trimAndLower) {
		return fmt.Errorf("expected Transformer to normalize strings before comparison")
	}

	// 7. cmpopts.EquateEmpty treats nil and empty slices or maps as equal in cmp.Equal
	var nilSlice []int
	emptySlice := []int{}
	if cmp.Equal(nilSlice, emptySlice) {
		return fmt.Errorf("expected nil and empty slice to differ by default")
	}
	if !cmp.Equal(nilSlice, emptySlice, cmpopts.EquateEmpty()) {
		return fmt.Errorf("expected EquateEmpty to equate nil and empty slice")
	}

	return nil
}