go.opentelemetry.io/otel v1.42.0: ErrorHandlerFunc

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 go.opentelemetry.io/otel.ErrorHandlerFunc in pkg:golang/go.opentelemetry.io/otel@v1.42.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/otel@v1.42.0
Demonstrate these symbols/APIs:
  - go.opentelemetry.io/otel.ErrorHandlerFunc

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:d479efe2ec0a53b4a72e24c682ea3464eb424ee031f9fa3ce539a15b0d5a04ec","contract":["otel.ErrorHandlerFunc wraps an ordinary function into an ErrorHandler interface implementation","otel.SetErrorHandler registers an ErrorHandlerFunc that receives errors passed to otel.Handle","otel.GetErrorHandler returns the registered ErrorHandlerFunc implementation","otel.ErrorHandlerFunc handles error dispatch safely including nil errors","otel.ErrorHandlerFunc handles concurrent error dispatches across goroutines"],"goal":"verify go.opentelemetry.io/otel.ErrorHandlerFunc in pkg:golang/go.opentelemetry.io/otel@v1.42.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel@v1.42.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel.ErrorHandlerFunc"]},"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/go.opentelemetry.io/otel@v1.42.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/otel@v1.42.0","symbols":["go.opentelemetry.io/otel.ErrorHandlerFunc"],"verifierAdapter":"golang@1"}

module sample

go 1.25.0

require go.opentelemetry.io/otel v1.42.0

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/go-logr/logr v1.4.3 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
	go.opentelemetry.io/otel/metric v1.42.0 // indirect
	go.opentelemetry.io/otel/trace v1.42.0 // indirect
)

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/otel v1.42.0 h1:lSQGzTgVR3+sgJDAU/7/ZMjN9Z+vUip7leaqBKy4sho=
go.opentelemetry.io/otel v1.42.0/go.mod h1:lJNsdRMxCUIWuMlVJWzecSMuNjE7dOYyWlqOXWkdqCc=
go.opentelemetry.io/otel/metric v1.42.0 h1:2jXG+3oZLNXEPfNmnpxKDeZsFI5o4J+nz6xUlaFdF/4=
go.opentelemetry.io/otel/metric v1.42.0/go.mod h1:RlUN/7vTU7Ao/diDkEpQpnz3/92J9ko05BIwxYa2SSI=
go.opentelemetry.io/otel/trace v1.42.0 h1:OUCgIPt+mzOnaUTpOQcBiM/PLQ/Op7oq6g4LenLmOYY=
go.opentelemetry.io/otel/trace v1.42.0/go.mod h1:f3K9S+IFqnumBkKhRJMeaZeNk9epyhnCmQh/EysQCdc=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"errors"
	"fmt"

	"go.opentelemetry.io/otel"
)

func main() {
	var captured error
	handler := otel.ErrorHandlerFunc(func(err error) {
		captured = err
		fmt.Printf("Received error via ErrorHandlerFunc: %v\n", err)
	})

	otel.SetErrorHandler(handler)
	otel.Handle(errors.New("example operation failed"))
}

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/otel.ErrorHandlerFunc in pkg:golang/go.opentelemetry.io/otel@v1.42.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/otel@v1.42.0"
  ],
  "symbols": [
    "go.opentelemetry.io/otel.ErrorHandlerFunc"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"
	"sync"
	"sync/atomic"

	"go.opentelemetry.io/otel"
)

func main() {
	origHandler := otel.GetErrorHandler()
	defer otel.SetErrorHandler(origHandler)

	// Assertion 1: otel.ErrorHandlerFunc wraps an ordinary function into an ErrorHandler interface implementation
	var fnInvoked bool
	var fn otel.ErrorHandler = otel.ErrorHandlerFunc(func(err error) {
		fnInvoked = true
	})
	fn.Handle(errors.New("direct invocation"))
	if !fnInvoked {
		fmt.Fprintf(os.Stderr, "FAIL: ErrorHandlerFunc did not invoke underlying function\n")
		os.Exit(1)
	}

	// Assertion 2: otel.SetErrorHandler registers an ErrorHandlerFunc that receives errors passed to otel.Handle
	var receivedErr error
	customHandler := otel.ErrorHandlerFunc(func(err error) {
		receivedErr = err
	})
	otel.SetErrorHandler(customHandler)
	testErr := errors.New("otel handled error")
	otel.Handle(testErr)
	if !errors.Is(receivedErr, testErr) {
		fmt.Fprintf(os.Stderr, "FAIL: expected %v, got %v\n", testErr, receivedErr)
		os.Exit(1)
	}

	// Assertion 3: otel.GetErrorHandler returns the registered ErrorHandlerFunc implementation
	currentHandler := otel.GetErrorHandler()
	if currentHandler == nil {
		fmt.Fprintf(os.Stderr, "FAIL: GetErrorHandler returned nil\n")
		os.Exit(1)
	}

	// Assertion 4: otel.ErrorHandlerFunc handles error dispatch safely including nil errors
	var nilHandled bool
	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) {
		if err == nil {
			nilHandled = true
		}
	}))
	otel.Handle(nil)
	if !nilHandled {
		fmt.Fprintf(os.Stderr, "FAIL: nil error was not dispatched to ErrorHandlerFunc\n")
		os.Exit(1)
	}

	// Assertion 5: otel.ErrorHandlerFunc handles concurrent error dispatches across goroutines
	var totalCalls int64
	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) {
		atomic.AddInt64(&totalCalls, 1)
	}))

	const goroutines = 20
	const iterations = 50
	var wg sync.WaitGroup
	for i := 0; i < goroutines; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := 0; j < iterations; j++ {
				otel.Handle(errors.New("concurrent error"))
			}
		}()
	}
	wg.Wait()

	expectedTotal := int64(goroutines * iterations)
	if actual := atomic.LoadInt64(&totalCalls); actual != expectedTotal {
		fmt.Fprintf(os.Stderr, "FAIL: expected %d total calls, got %d\n", expectedTotal, actual)
		os.Exit(1)
	}

	fmt.Println("PASS: all ErrorHandlerFunc contract assertions passed.")
}