github.com/cenkalti/backoff/v5 v5.0.3: Permanent

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/cenkalti/backoff/v5.Permanent in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Demonstrate these symbols/APIs:
  - github.com/cenkalti/backoff/v5.Permanent

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:sha256:7f24a9483bb00e4addd096c35d5e3da87b5ce98d41a42d607a2eb17a501c32ba","contract":["Permanent wraps a non-nil error into a PermanentError matching errors.As","Permanent returns nil when provided error is nil","Permanent error unwrap returns the original underlying error and matches errors.Is","Permanent error delegates Error string representation to the wrapped error","Permanent error returned from operation stops backoff.Retry immediately without subsequent retries"],"goal":"verify github.com/cenkalti/backoff/v5.Permanent in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","kind":"HOW","packages":["pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"symbols":["github.com/cenkalti/backoff/v5.Permanent"]},"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/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"subject":"pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","symbols":["github.com/cenkalti/backoff/v5.Permanent"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/cenkalti/backoff/v5 v5.0.3

github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=

package main

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/cenkalti/backoff/v5"
)

var (
	errTransient = errors.New("temporary connection glitch")
	errPermanent = errors.New("invalid request parameters")
)

func performOperation(attempt int) (string, error) {
	if attempt < 2 {
		return "", errTransient
	}
	return "", backoff.Permanent(errPermanent)
}

func main() {
	ctx := context.Background()
	attemptCount := 0

	op := func() (string, error) {
		attemptCount++
		fmt.Printf("Attempt %d...\n", attemptCount)
		return performOperation(attemptCount)
	}

	result, err := backoff.Retry(
		ctx,
		op,
		backoff.WithBackOff(backoff.NewConstantBackOff(10*time.Millisecond)),
		backoff.WithMaxTries(5),
	)

	if err != nil {
		fmt.Printf("Operation stopped with error: %v\n", err)
		if errors.Is(err, errPermanent) {
			fmt.Println("Permanent error encountered; retries halted as expected.")
		}
	} else {
		fmt.Printf("Operation succeeded with result: %s\n", result)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/cenkalti/backoff/v5.Permanent in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"
  ],
  "symbols": [
    "github.com/cenkalti/backoff/v5.Permanent"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/cenkalti/backoff/v5"
)

func main() {
	// Assertion 1: Permanent wraps a non-nil error into a PermanentError matching errors.As
	{
		origErr := errors.New("underlying sentinel failure")
		pErr := backoff.Permanent(origErr)
		if pErr == nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: Permanent(origErr) returned nil\n")
			os.Exit(1)
		}

		var target *backoff.PermanentError
		if !errors.As(pErr, &target) {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: errors.As did not match *backoff.PermanentError\n")
			os.Exit(1)
		}
		if target.Err != origErr {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: target.Err mismatch, expected %v, got %v\n", origErr, target.Err)
			os.Exit(1)
		}
	}

	// Assertion 2: Permanent returns nil when provided error is nil
	{
		nilResult := backoff.Permanent(nil)
		if nilResult != nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: Permanent(nil) did not return nil: %v\n", nilResult)
			os.Exit(1)
		}
	}

	// Assertion 3: Permanent error unwrap returns the original underlying error and matches errors.Is
	{
		origErr := errors.New("wrapped custom error")
		pErr := backoff.Permanent(origErr)

		if !errors.Is(pErr, origErr) {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: errors.Is(pErr, origErr) returned false\n")
			os.Exit(1)
		}

		unwrapped := errors.Unwrap(pErr)
		if unwrapped != origErr {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: errors.Unwrap(pErr) did not return origErr\n")
			os.Exit(1)
		}
	}

	// Assertion 4: Permanent error delegates Error string representation to the wrapped error
	{
		msg := "non-recoverable hardware fault"
		origErr := errors.New(msg)
		pErr := backoff.Permanent(origErr)

		if pErr.Error() != msg {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: pErr.Error() = %q, expected %q\n", pErr.Error(), msg)
			os.Exit(1)
		}
	}

	// Assertion 5: Permanent error returned from operation stops backoff.Retry immediately without subsequent retries
	{
		ctx := context.Background()
		terminalErr := errors.New("stop now")
		attempts := 0

		_, err := backoff.Retry(
			ctx,
			func() (string, error) {
				attempts++
				return "", backoff.Permanent(terminalErr)
			},
			backoff.WithBackOff(backoff.NewConstantBackOff(10*time.Millisecond)),
			backoff.WithMaxTries(5),
		)

		if attempts != 1 {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: expected 1 attempt, got %d\n", attempts)
			os.Exit(1)
		}
		if !errors.Is(err, terminalErr) {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: returned error does not match terminalErr: %v\n", err)
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed successfully.")
}