github.com/google/go-cmp v0.5.7: cmp.Option

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.Option in pkg:golang/github.com/google/go-cmp@v0.5.7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/google/go-cmp@v0.5.7
Demonstrate these symbols/APIs:
  - github.com/google/go-cmp/cmp.Option

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:aae5874e72dfec9deb055c17e4fc69fa54cbd1142264de828a2d8d201651b9ba","contract":["cmp.Comparer returns a cmp.Option that customizes equality comparison","cmp.Transformer returns a cmp.Option that transforms values prior to comparison","cmp.Options satisfies cmp.Option and combines multiple Option values","cmp.FilterPath with cmp.Ignore produces a cmp.Option that ignores matching paths","cmp.AllowUnexported returns a cmp.Option permitting comparison of unexported struct fields"],"goal":"verify github.com/google/go-cmp/cmp.Option in pkg:golang/github.com/google/go-cmp@v0.5.7","kind":"HOW","packages":["pkg:golang/github.com/google/go-cmp@v0.5.7"],"schemaVersion":1,"symbols":["github.com/google/go-cmp/cmp.Option"]},"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@v0.5.7"],"schemaVersion":1,"subject":"pkg:golang/github.com/google/go-cmp@v0.5.7","symbols":["github.com/google/go-cmp/cmp.Option"],"verifierAdapter":"golang@1"}

module sample

go 1.22

require github.com/google/go-cmp v0.5.7

github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
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=

package main

import (
	"fmt"
	"math"
	"strings"

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

type Reading struct {
	Label string
	Level float64
}

type hiddenConfig struct {
	Port  int
	token string
}

func main() {
	var lowerOpt cmp.Option = cmp.Transformer("LowerLabel", strings.ToLower)
	var floatOpt cmp.Option = cmp.Comparer(func(x, y float64) bool {
		return math.Abs(x-y) < 1e-4
	})
	var combinedOpt cmp.Option = cmp.Options{lowerOpt, floatOpt}

	r1 := Reading{Label: "PRESSURE", Level: 101.3251}
	r2 := Reading{Label: "pressure", Level: 101.3252}

	if cmp.Equal(r1, r2, combinedOpt) {
		fmt.Println("Readings match with composite cmp.Option")
	}

	c1 := hiddenConfig{Port: 8080, token: "internal"}
	c2 := hiddenConfig{Port: 8080, token: "internal"}
	var exportOpt cmp.Option = cmp.AllowUnexported(hiddenConfig{})
	if cmp.Equal(c1, c2, exportOpt) {
		fmt.Println("Hidden configs match with AllowUnexported cmp.Option")
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/google/go-cmp/cmp.Option in pkg:golang/github.com/google/go-cmp@v0.5.7",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/google/go-cmp@v0.5.7"
  ],
  "symbols": [
    "github.com/google/go-cmp/cmp.Option"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"
	"strings"

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

type Reading struct {
	Label string
	Level float64
}

type AuditItem struct {
	ID       int
	Revision int64
}

type unexportedHolder struct {
	Code   int
	detail string
}

func main() {
	// 1. cmp.Comparer returns a cmp.Option that customizes equality comparison
	{
		type bucketVal int
		var opt cmp.Option = cmp.Comparer(func(a, b bucketVal) bool {
			return a/10 == b/10
		})
		if !cmp.Equal(bucketVal(31), bucketVal(38), opt) {
			fmt.Fprintln(os.Stderr, "cmp.Comparer option failed to equate values in the same range")
			os.Exit(1)
		}
		if cmp.Equal(bucketVal(31), bucketVal(41), opt) {
			fmt.Fprintln(os.Stderr, "cmp.Comparer option equated values in different ranges")
			os.Exit(1)
		}
	}

	// 2. cmp.Transformer returns a cmp.Option that transforms values prior to comparison
	{
		var opt cmp.Option = cmp.Transformer("NormalizeText", func(s string) string {
			return strings.ToLower(strings.TrimSpace(s))
		})
		if !cmp.Equal("  Alpha ", "alpha", opt) {
			fmt.Fprintln(os.Stderr, "cmp.Transformer option failed to equate normalized strings")
			os.Exit(1)
		}
		if cmp.Equal("  Alpha ", "beta", opt) {
			fmt.Fprintln(os.Stderr, "cmp.Transformer option equated distinct strings")
			os.Exit(1)
		}
	}

	// 3. cmp.Options satisfies cmp.Option and combines multiple Option values
	{
		var labelOpt cmp.Option = cmp.Transformer("Lower", strings.ToLower)
		var levelOpt cmp.Option = cmp.Comparer(func(a, b float64) bool {
			return math.Abs(a-b) < 1e-3
		})
		var composite cmp.Option = cmp.Options{labelOpt, levelOpt}

		a := Reading{Label: "VOLTAGE", Level: 5.0001}
		b := Reading{Label: "voltage", Level: 5.0002}
		c := Reading{Label: "voltage", Level: 6.0}

		if !cmp.Equal(a, b, composite) {
			fmt.Fprintln(os.Stderr, "cmp.Options composite failed to equate matching readings")
			os.Exit(1)
		}
		if cmp.Equal(a, c, composite) {
			fmt.Fprintln(os.Stderr, "cmp.Options composite equated distinct readings")
			os.Exit(1)
		}
	}

	// 4. cmp.FilterPath with cmp.Ignore produces a cmp.Option that ignores matching paths
	{
		var ignoreRev cmp.Option = cmp.FilterPath(func(p cmp.Path) bool {
			return p.Last().String() == ".Revision"
		}, cmp.Ignore())

		x1 := AuditItem{ID: 5, Revision: 1}
		x2 := AuditItem{ID: 5, Revision: 42}
		x3 := AuditItem{ID: 9, Revision: 1}

		if !cmp.Equal(x1, x2, ignoreRev) {
			fmt.Fprintln(os.Stderr, "cmp.FilterPath with cmp.Ignore failed to ignore Revision field")
			os.Exit(1)
		}
		if cmp.Equal(x1, x3, ignoreRev) {
			fmt.Fprintln(os.Stderr, "cmp.FilterPath with cmp.Ignore equated items with different IDs")
			os.Exit(1)
		}
	}

	// 5. cmp.AllowUnexported returns a cmp.Option permitting comparison of unexported struct fields
	{
		u1 := unexportedHolder{Code: 1, detail: "alpha"}
		u2 := unexportedHolder{Code: 1, detail: "alpha"}
		u3 := unexportedHolder{Code: 1, detail: "beta"}

		var allowOpt cmp.Option = cmp.AllowUnexported(unexportedHolder{})
		if !cmp.Equal(u1, u2, allowOpt) {
			fmt.Fprintln(os.Stderr, "cmp.AllowUnexported failed to equate matching unexported fields")
			os.Exit(1)
		}
		if cmp.Equal(u1, u3, allowOpt) {
			fmt.Fprintln(os.Stderr, "cmp.AllowUnexported equated differing unexported fields")
			os.Exit(1)
		}
	}

	fmt.Println("contract ok")
}