initial commit

error.go

@@ -0,0 +1,104 @@
+package adverr
+
+import (
+	"errors"
+	"reflect"
+	"strings"
+)
+
+// Error is a wrapper for error with stack trace
+type Error struct {
+	msg       string
+	callTrace *CallTrace
+	tmpl      *ErrTmpl
+	cause     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),
+	}
+}
+
+// Wrap returns a new Error with the given message which is caused by cause
+func Wrap(msg string, cause error) *Error {
+	return &Error{
+		msg:       msg,
+		cause:     cause,
+		callTrace: Trace(2),
+	}
+}
+
+func errtype(err error) string {
+	if e, ok := err.(*Error); ok && e.tmpl != nil {
+		return errtype(e.tmpl)
+	} else if tmpl, ok := err.(*ErrTmpl); ok {
+		t := reflect.TypeOf(tmpl)
+		for t.Kind() == reflect.Ptr {
+			t = t.Elem()
+		}
+		return t.PkgPath() + "." + tmpl.name
+	}
+
+	t := reflect.TypeOf(err)
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t.PkgPath() + "." + t.Name()
+}
+
+func (e *Error) Unwrap() error {
+	return e.cause
+}
+
+func (e *Error) Error() string {
+	b := new(strings.Builder)
+	printErr(e, b)
+	return b.String()
+}
+
+// Is implements the error equality function used by errors.Is()
+// It returns true if the error is the same instance or is created using the same ErrTmpl
+func (e *Error) Is(target error) bool {
+	// same error instance
+	if target == e {
+		return true
+	}
+
+	// no template used, therefore no equality possible
+	if e.tmpl == nil {
+		return false
+	}
+
+	// same template, therefore errors are equal to another
+	if tErr, ok := target.(*Error); ok {
+		return tErr.tmpl == e.tmpl
+	}
+
+	return false
+}
+
+func printErr(err error, b *strings.Builder) {
+	if e, ok := err.(*Error); ok {
+		b.WriteString(errtype(e))
+		b.WriteString(": ")
+		b.WriteString(e.msg)
+		b.WriteString("\n")
+		b.WriteString(e.callTrace.String())
+	} else {
+		b.WriteString(errtype(err))
+		b.WriteString(": ")
+		b.WriteString(err.Error())
+		b.WriteString("\n")
+	}
+
+	cause := errors.Unwrap(err)
+	if cause != nil {
+		b.WriteString("Caused by ")
+		printErr(cause, b)
+	}
+}