std.go

package errors

import stderrors "errors"

// ErrUnsupported indicates that a requested operation cannot be performed,
// because it is unsupported. For example, a call to [os.Link] when using a
// file system that does not support hard links.
//
// Functions and methods should not return this error but should instead
// return an error including appropriate context that satisfies
//
//	errors.Is(err, errors.ErrUnsupported)
//
// either by directly wrapping ErrUnsupported or by implementing an [Is] method.
//
// Functions and methods should document the cases in which an error
// wrapping this will be returned.
//
//goland:noinspection GoUnusedGlobalVariable
var ErrUnsupported = stderrors.ErrUnsupported

// Join returns an error that wraps the given errors.
// Any nil error values are discarded.
// Join returns nil if every value in errs is nil.
// The error formats as the concatenation of the strings obtained
// by calling the Error method of each element of errs, with a newline
// between each string.
//
// A non-nil error returned by Join implements the Unwrap() []error method.
//
//goland:noinspection GoUnusedExportedFunction
func Join(errs ...error) error { return stderrors.Join(errs...) }

// Unwrap returns the result of calling the Unwrap method on err, if err's
// type contains an Unwrap method returning error.
// Otherwise, Unwrap returns nil.
//
// Unwrap only calls a method of the form "Unwrap() error".
// In particular Unwrap does not unwrap errors returned by [Join].
//
//goland:noinspection GoUnusedExportedFunction
func Unwrap(err error) error { return stderrors.Unwrap(err) }

// Is reports whether any error in err's tree matches target.
//
// The tree consists of err itself, followed by the errors obtained by repeatedly
// calling its Unwrap() error or Unwrap() []error method. When err wraps multiple
// errors, Is examines err followed by a depth-first traversal of its children.
//
// An error is considered to match a target if it is equal to that target or if
// it implements a method Is(error) bool such that Is(target) returns true.
//
// An error type might provide an Is method so it can be treated as equivalent
// to an existing error. For example, if MyError defines
//
//	func (m MyError) Is(target error) bool { return target == fs.ErrExist }
//
// then Is(MyError{}, fs.ErrExist) returns true. See [syscall.Errno.Is] for
// an example in the standard library. An Is method should only shallowly
// compare err and the target and not call [Unwrap] on either.
//
//goland:noinspection GoUnusedExportedFunction
func Is(err, target error) bool { return stderrors.Is(err, target) }

// As finds the first error in err's tree that matches target, and if one is found, sets
// target to that error value and returns true. Otherwise, it returns false.
//
// The tree consists of err itself, followed by the errors obtained by repeatedly
// calling its Unwrap() error or Unwrap() []error method. When err wraps multiple
// errors, As examines err followed by a depth-first traversal of its children.
//
// An error matches target if the error's concrete value is assignable to the value
// pointed to by target, or if the error has a method As(interface{}) bool such that
// As(target) returns true. In the latter case, the As method is responsible for
// setting target.
//
// An error type might provide an As method so it can be treated as if it were a
// different error type.
//
// As panics if target is not a non-nil pointer to either a type that implements
// error, or to any interface type.
//
//goland:noinspection GoUnusedExportedFunction
func As(err error, target any) bool {
	//goland:noinspection GoErrorsAs
	return stderrors.As(err, target)
}