compose/multierror/multierror.go

package multierror

import (
	"strings"

	"github.com/hashicorp/go-multierror"
)

// Error wraps a multierror.Error and defines a default
// formatting function that fits cli needs
type Error struct {
	err *multierror.Error
}

func (e *Error) Error() string {
	if e == nil || e.err == nil {
		return ""
	}
	e.err.ErrorFormat = listErrorFunc
	return e.err.Error()
}

// WrappedErrors returns the list of errors that this Error is wrapping.
// It is an implementation of the errwrap.Wrapper interface so that
// multierror.Error can be used with that library.
//
// This method is not safe to be called concurrently and is no different
// than accessing the Errors field directly. It is implemented only to
// satisfy the errwrap.Wrapper interface.
func (e *Error) WrappedErrors() []error {
	return e.err.WrappedErrors()
}

// Unwrap returns an error from Error (or nil if there are no errors)
func (e *Error) Unwrap() error {
	if e == nil || e.err == nil {
		return nil
	}
	return e.err.Unwrap()
}

// ErrorOrNil returns an error interface if this Error represents
// a list of errors, or returns nil if the list of errors is empty. This
// function is useful at the end of accumulation to make sure that the value
// returned represents the existence of errors.
func (e *Error) ErrorOrNil() error {
	if e == nil || e.err == nil {
		return nil
	}
	if len(e.err.Errors) == 0 {
		return nil
	}

	return e
}

// Append adds an error to a multierror, if err is
// not a multierror it will be converted to one
func Append(err error, errs ...error) *Error {
	switch err := err.(type) {
	case *Error:
		if err == nil {
			err = new(Error)
		}
		for _, e := range errs {
			err.err = multierror.Append(err.err, e)
		}
		return err
	default:
		newErrs := make([]error, 0, len(errs)+1)
		if err != nil {
			newErrs = append(newErrs, err)
		}
		newErrs = append(newErrs, errs...)

		return Append(&Error{}, newErrs...)
	}
}

func listErrorFunc(errs []error) string {
	if len(errs) == 1 {
		return errs[0].Error()
	}

	messages := make([]string, len(errs))

	for i, err := range errs {
		messages[i] = "Error: " + err.Error()
	}

	return strings.Join(messages, "\n")
}