Combine Go Errors

combine_errors.go

package main

import (
	"testing"

	"github.com/pkg/errors"
	"github.com/stretchr/testify/assert"
)

func combineErrors(errs ...error) error {
	messages := []string{}
	var nonNilErr error
	for _, err := range errs {
		if err != nil {
			messages = append(messages, "["+err.Error()+"]")
			nonNilErr = err
		}
	}
	if len(messages) == 0 {
		return nil
	}
	if len(messages) == 1 {
		return nonNilErr
	}
	return errors.New(strings.Join(messages, " + "))
}


func TestCombineErrors(t *testing.T) {
	err1 := errors.New("err1")
	err2 := errors.New("err2")
	err3 := errors.New("err3")

	err := combineErrors(err1, err2, err3)
	assert.EqualError(t, err, "[err1] + [err2] + [err3]")

	err = combineErrors(err1, nil, err3)
	assert.EqualError(t, err, "[err1] + [err3]")

	err = combineErrors(nil, nil, err3)
	assert.EqualError(t, err, "err3")

	err = combineErrors(nil, nil, nil)
	assert.NoError(t, err)
}