Testing errorlint

README.md

Error wrapping test

$ golangci-lint --version
golangci-lint has version 1.32.2 built from 52d26a3 on 2020-11-03T01:15:38Z

$ golangci-lint run --enable-all ./...
main.go:33:45: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
        return fmt.Errorf("%w: %s", ErrFooFailed, err.Error())
                                                  ^

main.go

package main

import (
	"errors"
	"fmt"
	"log"
)

/*
 * Pretend this in in "package foo".
 */
var (
	// ErrParsingError is in the foo package.
	ErrParsingError = errors.New("parsing error")
)

// Foo is in a different package.
func Foo() error {
	return fmt.Errorf("%w at position 10", ErrParsingError)
}

/*
 * Pretend this in in "package bar".
 */
var (
	// ErrFooFailed is in the bar package.
	ErrFooFailed = errors.New("foo failed")
)

// Bar is in this package.
func Bar() error {
	if err := Foo(); err != nil {
		return fmt.Errorf("%w: %s", ErrFooFailed, err.Error())
	}

	return nil
}

/*
 * Pretend this in in "package main", even though it is.
 */
func main() {
	log.Println("Starting")

	if err := Bar(); err != nil {
		if errors.Is(err, ErrFooFailed) {
			log.Print(err)
		} else {
			log.Printf("Unknown error: %s", err.Error())
		}
	}

	log.Println("Finished")
}