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package errs
import (
"fmt"
"io"
)
// Group is a list of errors.
type Group []error
// Combine combines multiple non-empty errors into a single error.
func Combine(errs ...error) error {
var group Group
group.Add(errs...)
return group.Err()
}
// Add adds non-empty errors to the Group.
func (group *Group) Add(errs ...error) {
for _, err := range errs {
if err != nil {
*group = append(*group, err)
}
}
}
// Err returns an error containing all of the non-nil errors.
// If there was only one error, it will return it.
// If there were none, it returns nil.
func (group Group) Err() error {
sanitized := group.sanitize()
if len(sanitized) == 0 {
return nil
}
if len(sanitized) == 1 {
return sanitized[0]
}
return combinedError(sanitized)
}
// sanitize returns group that doesn't contain nil-s
func (group Group) sanitize() Group {
// sanity check for non-nil errors
for i, err := range group {
if err == nil {
sanitized := make(Group, 0, len(group)-1)
sanitized = append(sanitized, group[:i]...)
sanitized.Add(group[i+1:]...)
return sanitized
}
}
return group
}
// combinedError is a list of non-empty errors
type combinedError []error
// Unwrap returns the first error.
func (group combinedError) Unwrap() []error { return group }
// Error returns error string delimited by semicolons.
func (group combinedError) Error() string { return fmt.Sprintf("%v", group) }
// Format handles the formatting of the error. Using a "+" on the format
// string specifier will cause the errors to be formatted with "+" and
// delimited by newlines. They are delimited by semicolons otherwise.
func (group combinedError) Format(f fmt.State, c rune) {
delim := "; "
if f.Flag(int('+')) {
io.WriteString(f, "group:\n--- ")
delim = "\n--- "
}
for i, err := range group {
if i != 0 {
io.WriteString(f, delim)
}
if formatter, ok := err.(fmt.Formatter); ok {
formatter.Format(f, c)
} else {
fmt.Fprintf(f, "%v", err)
}
}
}
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