74 lines
2 KiB
Go
74 lines
2 KiB
Go
// Package errors provides error handling utilites.
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package errors
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import (
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"reflect"
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)
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// WalkFunc is the signature of the Walk callback function. The function gets the
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// current error in the chain and should return true if the chain processing
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// should be aborted.
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type WalkFunc func(error) bool
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// Walk invokes the given function for each error in the chain. If the
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// provided functions returns true or no further cause can be found, the process
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// is stopped and no further calls will be made.
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//
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// The next error in the chain is determined by the following rules:
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//
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// the return value of this method is used.
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// - If the current error has a `Unwrap() error` method
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// the return value of this method is used.
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// - If the current error has a `Unwrap() []error` method
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// the return values of this method is used.
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// - Common errors in the Go runtime that contain an Err field will use this value.
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func Walk(err error, f WalkFunc) {
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for prev := err; err != nil; prev = err {
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if f(err) {
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return
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}
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switch e := err.(type) {
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case multiWrapper:
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for _, err = range e.Unwrap() {
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Walk(err, f)
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}
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return
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case causer:
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err = e.Cause()
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case wrapper:
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err = e.Unwrap()
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default:
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// Unpack any struct or *struct with a field of name Err which satisfies
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// the error interface. This includes *url.Error, *net.OpError,
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// *os.SyscallError and many others in the stdlib.
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errType := reflect.TypeOf(err)
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errValue := reflect.ValueOf(err)
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if errValue.IsValid() && errType.Kind() == reflect.Ptr {
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errType = errType.Elem()
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errValue = errValue.Elem()
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}
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if errValue.IsValid() && errType.Kind() == reflect.Struct {
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if errField := errValue.FieldByName("Err"); errField.IsValid() {
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errFieldValue := errField.Interface()
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if newErr, ok := errFieldValue.(error); ok {
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err = newErr
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}
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}
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}
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}
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if reflect.DeepEqual(err, prev) {
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break
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}
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}
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}
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type causer interface {
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Cause() error
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}
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type wrapper interface {
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Unwrap() error
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}
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type multiWrapper interface {
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Unwrap() []error
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}
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