Better error handling, many fixes all around

gemini/errors.go

@@ -5,13 +5,13 @@ import (
 	"fmt"
 )
 
-type ErrGeminiStatusCode struct {
+type GeminiError struct {
 	Msg    string
 	Code   int
 	Header string
 }
 
-func (e *ErrGeminiStatusCode) Error() string {
+func (e *GeminiError) Error() string {
 	return fmt.Sprintf("%s: %s", e.Msg, e.Header)
 }
 
@@ -31,7 +31,7 @@ func NewErrGeminiStatusCode(code int, header string) error {
 	default:
 		msg = "unexpected status code"
 	}
-	return &ErrGeminiStatusCode{
+	return &GeminiError{
 		Msg:    msg,
 		Code:   code,
 		Header: header,
@@ -39,7 +39,6 @@ func NewErrGeminiStatusCode(code int, header string) error {
 }
 
 var (
-	ErrGemini                 = errors.New("gemini general error")
 	ErrGeminiRobotsParse      = errors.New("gemini robots.txt parse error")
 	ErrGeminiRobotsDisallowed = errors.New("gemini robots.txt disallowed")
 	ErrGeminiResponseHeader   = errors.New("gemini response header error")
@@ -64,8 +63,10 @@ var (
 // we would lose ability to check wrapped
 // errors via errors.Is().
 
-var KnownErrors = []error{
-	ErrGemini,
+var errGemini *GeminiError
+
+var knownErrors = []error{ //nolint:gochecknoglobals
+	errGemini,
 	ErrGeminiLinkLineParse,
 	ErrGeminiRobotsParse,
 	ErrGeminiRobotsDisallowed,
@@ -87,14 +88,14 @@ var KnownErrors = []error{
 }
 
 func IsKnownError(err error) bool {
-	var errGeminiStatusCode *ErrGeminiStatusCode
-	if errors.As(err, &errGeminiStatusCode) {
-		return true
-	}
-	for _, known := range KnownErrors {
+	for _, known := range knownErrors {
 		if errors.Is(err, known) {
 			return true
 		}
 	}
+	// Check for wrapped errors as well
+	if errors.As(err, new(*GeminiError)) {
+		return true
+	}
 	return false
 }