chained errors introduced

error.go

@@ -12,14 +12,13 @@ type Error struct {
 	callTrace *CallTrace
 	tmpl      *ErrTmpl
 	cause     error
+	prev      []error
 }
 
 // New returns a new Error with the given message
 func New(msg string) *Error {
 	return &Error{
 		msg:       msg,
-		cause:     nil,
-		tmpl:      nil,
 		callTrace: Trace(2),
 	}
 }
@@ -33,6 +32,16 @@ func Wrap(msg string, cause error) *Error {
 	}
 }
 
+// Chain returns a new Error with the given message and a slice of errors
+// which were caused in the same function in succession
+func Chain(msg string, errors []error) *Error {
+	return &Error{
+		msg:       msg,
+		callTrace: Trace(2),
+		prev:      errors,
+	}
+}
+
 func errtype(err error) string {
 	if e, ok := err.(*Error); ok && e.tmpl != nil {
 		return errtype(e.tmpl)
@@ -83,8 +92,43 @@ func (e *Error) Is(target error) bool {
 	return false
 }
 
+// Get Returns the first error in the chain for which errors.Is(target) returns true
+func (e *Error) Get(target error) error {
+	if e.prev == nil {
+		return nil
+	}
+
+	for _, prevErr := range e.prev {
+		if errors.Is(prevErr, target) {
+			return prevErr
+		}
+	}
+	return nil
+}
+
+// GetByIndex returns the i'th error in the chain
+func (e *Error) GetByIndex(i int) error {
+	if e.prev == nil {
+		return nil
+	}
+	return e.prev[i]
+}
+
+// Contains is a shorthand for Get(target) != nil.
+// Can be considered as an errors.Is function but for chains instead of causes
+func (e *Error) Contains(target error) bool {
+	return e.Get(target) != nil
+}
+
+// Chain returns a slice of all chained errors
+func (e *Error) Chain() []error {
+	return e.prev[:]
+}
+
 func printErr(err error, b *strings.Builder) {
-	if e, ok := err.(*Error); ok {
+	e, ok := err.(*Error)
+
+	if ok {
 		b.WriteString(errtype(e))
 		b.WriteString(": ")
 		b.WriteString(e.msg)
@@ -94,7 +138,8 @@ func printErr(err error, b *strings.Builder) {
 		b.WriteString(errtype(err))
 		b.WriteString(": ")
 		b.WriteString(err.Error())
-		b.WriteString("\n\t(Unknown source)\n")
+		b.WriteString("\n")
+		b.WriteString("\t(Unknown source)\n")
 	}
 
 	cause := errors.Unwrap(err)
@@ -102,4 +147,11 @@ func printErr(err error, b *strings.Builder) {
 		b.WriteString("Caused by ")
 		printErr(cause, b)
 	}
+
+	if ok {
+		for _, prevErr := range e.prev {
+			b.WriteString("Previously thrown ")
+			printErr(prevErr, b)
+		}
+	}
 }