mirror of https://github.com/knative/docs.git
97 lines
2.6 KiB
Go
97 lines
2.6 KiB
Go
package protocol
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import (
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"errors"
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"fmt"
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)
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// Result leverages go's 1.13 error wrapping.
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type Result error
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// Is reports whether any error in err's chain matches target.
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//
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// The chain consists of err itself followed by the sequence of errors obtained by
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// repeatedly calling Unwrap.
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//
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// An error is considered to match a target if it is equal to that target or if
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// it implements a method Is(error) bool such that Is(target) returns true.
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// (text from errors/wrap.go)
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var ResultIs = errors.Is
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// As finds the first error in err's chain that matches target, and if so, sets
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// target to that error value and returns true.
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//
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// The chain consists of err itself followed by the sequence of errors obtained by
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// repeatedly calling Unwrap.
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//
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// An error matches target if the error's concrete value is assignable to the value
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// pointed to by target, or if the error has a method As(interface{}) bool such that
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// As(target) returns true. In the latter case, the As method is responsible for
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// setting target.
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//
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// As will panic if target is not a non-nil pointer to either a type that implements
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// error, or to any interface type. As returns false if err is nil.
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// (text from errors/wrap.go)
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var ResultAs = errors.As
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func NewResult(messageFmt string, args ...interface{}) Result {
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return fmt.Errorf(messageFmt, args...) // TODO: look at adding ACK/Nak support.
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}
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func IsACK(target Result) bool {
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// special case, nil target also means ACK.
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if target == nil {
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return true
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}
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return ResultIs(target, ResultACK)
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}
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func IsNACK(target Result) bool {
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return ResultIs(target, ResultNACK)
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}
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var (
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ResultACK = NewReceipt(true, "")
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ResultNACK = NewReceipt(false, "")
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)
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// NewReceipt returns a fully populated protocol Receipt that should be used as
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// a transport.Result. This type holds the base ACK/NACK results.
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func NewReceipt(ack bool, messageFmt string, args ...interface{}) Result {
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return &Receipt{
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ACK: ack,
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Format: messageFmt,
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Args: args,
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}
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}
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// Receipt wraps the fields required to understand if a protocol event is acknowledged.
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type Receipt struct {
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ACK bool
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Format string
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Args []interface{}
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}
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// make sure Result implements error.
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var _ error = (*Receipt)(nil)
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// Is returns if the target error is a Result type checking target.
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func (e *Receipt) Is(target error) bool {
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if o, ok := target.(*Receipt); ok {
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if e.ACK == o.ACK {
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return true
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}
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return false
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}
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// Allow for wrapped errors.
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err := fmt.Errorf(e.Format, e.Args...)
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return errors.Is(err, target)
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}
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// Error returns the string that is formed by using the format string with the
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// provided args.
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func (e *Receipt) Error() string {
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return fmt.Sprintf(e.Format, e.Args...)
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}
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