github.com/pkg/errors v0.9.1

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/pkg/errors@v0.9.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/pkg/errors@v0.9.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:ee9bf7dd4bfbaa2af1da9bfb6bf54b76eab2a11455a930614bb3bfa90008757f","contract":["errors.New and errors.Errorf create errors with stack trace capture and formatted messages","errors.Wrap and errors.Wrapf annotate an error with context message and stack trace, returning nil for a nil error","errors.WithMessage and errors.WithMessagef add context message without altering the cause, returning nil for a nil error","errors.WithStack attaches stack trace information to an existing error without altering its message","errors.Cause recursively unwraps nested wrapped errors to retrieve the root underlying cause","Formatting wrapped errors with %+v outputs the full multi-frame stack trace"],"goal":"verify pkg:golang/github.com/pkg/errors@v0.9.1","kind":"HOW","packages":["pkg:golang/github.com/pkg/errors@v0.9.1"],"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/pkg/errors@v0.9.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/pkg/errors@v0.9.1","verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/pkg/errors v0.9.1

github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=

package main

import (
	"fmt"

	"github.com/pkg/errors"
)

func parseConfig(filename string) error {
	return errors.Errorf("file %q not found", filename)
}

func initializeService() error {
	err := parseConfig("config.json")
	if err != nil {
		return errors.Wrap(err, "failed to initialize service")
	}
	return nil
}

func main() {
	err := initializeService()
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		fmt.Printf("Cause: %v\n", errors.Cause(err))
		fmt.Printf("Stack trace:\n%+v\n", err)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/pkg/errors@v0.9.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/pkg/errors@v0.9.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"fmt"
	"os"
	"strings"

	"github.com/pkg/errors"
)

func main() {
	if err := runContract(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract verification failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All pkg/errors contract assertions passed successfully.")
}

func runContract() error {
	// 1. errors.New and errors.Errorf create errors with stack trace and formatting
	newErr := errors.New("base error message")
	if newErr == nil || newErr.Error() != "base error message" {
		return fmt.Errorf("errors.New failed, got: %v", newErr)
	}

	formattedErr := errors.Errorf("formatted error with code %d", 404)
	if formattedErr == nil || formattedErr.Error() != "formatted error with code 404" {
		return fmt.Errorf("errors.Errorf failed, got: %v", formattedErr)
	}

	formattedStackTrace := fmt.Sprintf("%+v", formattedErr)
	if !strings.Contains(formattedStackTrace, "contract.go") {
		return fmt.Errorf("expected stack trace from errors.Errorf to contain 'contract.go', got:\n%s", formattedStackTrace)
	}

	// 2. errors.Wrap and errors.Wrapf annotate error with context and stack trace, nil safety
	if errors.Wrap(nil, "ignored context") != nil {
		return fmt.Errorf("expected errors.Wrap(nil, ...) to return nil")
	}
	if errors.Wrapf(nil, "ignored %s", "context") != nil {
		return fmt.Errorf("expected errors.Wrapf(nil, ...) to return nil")
	}

	baseErr := errors.New("disk full")
	wrappedErr := errors.Wrap(baseErr, "write failed")
	if wrappedErr.Error() != "write failed: disk full" {
		return fmt.Errorf("expected 'write failed: disk full', got: %q", wrappedErr.Error())
	}

	wrappedFormattedErr := errors.Wrapf(baseErr, "write to device %s failed", "/dev/sda1")
	if wrappedFormattedErr.Error() != "write to device /dev/sda1 failed: disk full" {
		return fmt.Errorf("expected 'write to device /dev/sda1 failed: disk full', got: %q", wrappedFormattedErr.Error())
	}

	// 3. errors.WithMessage and errors.WithMessagef add context message without adding stack trace, nil safety
	if errors.WithMessage(nil, "ignored") != nil {
		return fmt.Errorf("expected errors.WithMessage(nil, ...) to return nil")
	}
	if errors.WithMessagef(nil, "ignored %d", 1) != nil {
		return fmt.Errorf("expected errors.WithMessagef(nil, ...) to return nil")
	}

	withMsgErr := errors.WithMessage(baseErr, "operation timeout")
	if withMsgErr.Error() != "operation timeout: disk full" {
		return fmt.Errorf("expected 'operation timeout: disk full', got: %q", withMsgErr.Error())
	}

	withMsgfErr := errors.WithMessagef(baseErr, "step %d failed", 2)
	if withMsgfErr.Error() != "step 2 failed: disk full" {
		return fmt.Errorf("expected 'step 2 failed: disk full', got: %q", withMsgfErr.Error())
	}

	// 4. errors.WithStack attaches stack trace without modifying message, nil safety
	if errors.WithStack(nil) != nil {
		return fmt.Errorf("expected errors.WithStack(nil) to return nil")
	}

	plainErr := fmt.Errorf("plain standard error")
	stackedErr := errors.WithStack(plainErr)
	if stackedErr.Error() != "plain standard error" {
		return fmt.Errorf("expected message preserved in WithStack, got: %q", stackedErr.Error())
	}
	stackedOutput := fmt.Sprintf("%+v", stackedErr)
	if !strings.Contains(stackedOutput, "contract.go") {
		return fmt.Errorf("expected WithStack output to include stack trace with contract.go, got:\n%s", stackedOutput)
	}

	// 5. errors.Cause recursively retrieves the root underlying error
	if errors.Cause(nil) != nil {
		return fmt.Errorf("expected errors.Cause(nil) to be nil")
	}

	rootErr := errors.New("root cause failure")
	layer1 := errors.WithMessage(rootErr, "layer 1")
	layer2 := errors.Wrap(layer1, "layer 2")
	layer3 := errors.WithStack(layer2)
	layer4 := errors.WithMessagef(layer3, "layer 4: attempt %d", 3)

	cause := errors.Cause(layer4)
	if cause != rootErr {
		return fmt.Errorf("expected Cause to return rootErr, got: %v", cause)
	}

	// 6. Formatting wrapped errors with %+v prints all layers and stack frames
	nestedOutput := fmt.Sprintf("%+v", layer2)
	if !strings.Contains(nestedOutput, "root cause failure") || !strings.Contains(nestedOutput, "layer 1") || !strings.Contains(nestedOutput, "layer 2") {
		return fmt.Errorf("expected %+v output to include all wrap messages, got:\n%s", nestedOutput)
	}

	return nil
}