package errors

Import Path
	errors (on golang.org and go.dev)

Dependency Relation
	imports one package, and imported by 84 packages


Involved Source Files

	
		Package errors implements functions to manipulate errors.

		The New function creates errors whose only content is a text message.

		The Unwrap, Is and As functions work on errors that may wrap other errors.
		An error wraps another error if its type has the method

			Unwrap() error

		If e.Unwrap() returns a non-nil error w, then we say that e wraps w.

		Unwrap unpacks wrapped errors. If its argument's type has an
		Unwrap method, it calls the method once. Otherwise, it returns nil.

		A simple way to create wrapped errors is to call fmt.Errorf and apply the %w verb
		to the error argument:

			errors.Unwrap(fmt.Errorf("... %w ...", ..., err, ...))

		returns err.

		Is unwraps its first argument sequentially looking for an error that matches the
		second. It reports whether it finds a match. It should be used in preference to
		simple equality checks:

			if errors.Is(err, fs.ErrExist)

		is preferable to

			if err == fs.ErrExist

		because the former will succeed if err wraps fs.ErrExist.

		As unwraps its first argument sequentially looking for an error that can be
		assigned to its second argument, which must be a pointer. If it succeeds, it
		performs the assignment and returns true. Otherwise, it returns false. The form

			var perr *fs.PathError
			if errors.As(err, &perr) {
				fmt.Println(perr.Path)
			}

		is preferable to

			if perr, ok := err.(*fs.PathError); ok {
				fmt.Println(perr.Path)
			}

		because the former will succeed if err wraps an *fs.PathError.

	      wrap.go


Code Examples

	
		package main
		
		import (
			"fmt"
			"time"
		)
		
		// MyError is an error implementation that includes a time and message.
		type MyError struct {
			When time.Time
			What string
		}
		
		func (e MyError) Error() string {
			return fmt.Sprintf("%v: %v", e.When, e.What)
		}
		
		func oops() error {
			return MyError{
				time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
				"the file system has gone away",
			}
		}
		
		func main() {
			if err := oops(); err != nil {
				fmt.Println(err)
			}
		}




Package-Level Type Names (only one, which is unexported)


	/* sort exporteds by:  |  */
	


Package-Level Functions (total 4, all are exported)


	
		As finds the first error in err's chain that matches target, and if so, sets
		target to that error value and returns true. Otherwise, it returns false.

		The chain consists of err itself followed by the sequence of errors obtained by
		repeatedly calling Unwrap.

		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.


	
		Is reports whether any error in err's chain matches target.

		The chain consists of err itself followed by the sequence of errors obtained by
		repeatedly calling Unwrap.

		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.


	
		New returns an error that formats as the given text.
		Each call to New returns a distinct error value even if the text is identical.


	
		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.




Package-Level Variables (only one, which is unexported)