README
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Overview ¶
Package errors provides error generators and helpers.
Index ¶
- Constants
- func AppendFunc(err error, fn ErrorFunc) error
- func AppendFuncs(err error, fns ...ErrorFunc) error
- func As(err error, target any) bool
- func Is(err error, target error) bool
- func Join(errs ...error) error
- func JoinFuncs(fns ...ErrorFunc) error
- func Lazy(fn ErrorFunc) error
- func New(text string) error
- func Newf(text string, args ...any) error
- func Unwrap(err error) error
- func Wrap(base error, msg string) error
- func Wrapf(base error, msg string, args ...any) error
- type ErrorFunc
Constants ¶
const Version = "v0.4.0"
Version is the current version of the errors package.
Variables ¶
This section is empty.
Functions ¶
func AppendFunc ¶ added in v0.4.0
AppendFunc evaluates fn and appends it to err. If either err or fn are nil, the other is returned. If fn returns a nil error, err is returned.
func AppendFuncs ¶ added in v0.4.0
AppendFuncs evaluates fns serially, appending each return value to err. Nil errors are ignored. If err and fns produce no non-nil errors, nil is returned; if only one non-nil error is produced, it is returned verbatim. Otherwise, the resulting non-nil errors are joined with Join.
func As ¶
As is a proxy for the standard library's errors.As.
As finds the first error in err's chain that matches target, and if one is found, 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.
func Is ¶
Is is a proxy for the standard library's errors.Is.
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. An Is method should only shallowly compare err and the target and not call Unwrap on either.
func Join ¶ added in v0.3.0
Join combines all given errors into a single error. Any nil values are discarded.
func JoinFuncs ¶ added in v0.4.0
JoinFuncs evaluates fns serially, joining all non-nil return values and returning the resulting error. If fns is empty or if all fns return nil, nil is returned; if only one error is produced, it is returned verbatim. Otherwise, the resulting errors are joined with Join.
func Lazy ¶ added in v0.4.0
Lazy returns an error that will lazily evaluate fn; that is, fn will be called at most once, and not until the resulting error would be used.
func New ¶
New is a proxy for the standard library's errors.New.
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.
func Newf ¶
Newf is a proxy for the standard library's fmt.Errorf.
Newf formats according to a format specifier and returns the string as a value that satisfies error.
If the format specifier includes a %w verb with an error operand, the returned error will implement an Unwrap method returning the operand. It is invalid to include more than one %w verb or to supply it with an operand that does not implement the error interface. The %w verb is otherwise a synonym for %v.
func Unwrap ¶
Unwrap is a proxy for the standard library's errors.Unwrap.
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.
func Wrap ¶
Wrap returns a new error that wraps base, using msg as its error message. Wrap produces an error of the format "msg: base" in order to provide the consistent and coherent layering of errors.
If base is nil, Wrap returns a nil error. If msg is an empty string, base is returned verbatim.
func Wrapf ¶
Wrapf returns a new error that wraps base, using msg and args to format its error message. Wrap produces an error of the format "msg: base", where msg includes the interpolation of all sprintf placeholders and variables, in order to provide the consistent and coherent layering of errors.
Wrapf supports wrapping errors with the %w verb.
If base is nil, Wrapf returns a nil error. If msg is an empty string and args is empty, base is returned verbatim.
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