proxy: imp err msg

proxy/upstreams.go

@@ -13,6 +13,8 @@ import (
 	"golang.org/x/exp/slices"
 )
 
+const errWrongUpstreamSpecs errors.Error = "wrong upstream specification"
+
 // UpstreamConfig is a wrapper for a list of default upstreams, a map of
 // reserved domains and corresponding upstreams.
 type UpstreamConfig struct {
@@ -119,7 +121,7 @@ var _ error = (*ParseError)(nil)
 
 // Error implements the [error] interface for *ParseError.
 func (e *ParseError) Error() (msg string) {
-	return fmt.Sprintf("index: %d: %s", e.Idx, e.err)
+	return fmt.Sprintf("parsing error at index %d: %s", e.Idx, e.err)
 }
 
 // type check
@@ -180,18 +182,18 @@ func (p *configParser) parse(conf []string) (c *UpstreamConfig, err error) {
 
 // parseLine returns an error if upstream configuration line is invalid.
 func (p *configParser) parseLine(idx int, confLine string) (err error) {
+	if len(confLine) == 0 || confLine[0] == '#' {
+		return nil
+	}
+
 	upstreams, domains, err := splitConfigLine(confLine)
 	if err != nil {
 		// Don't wrap the error since it's informative enough as is.
 		return err
 	}
 
-	if upstreams[0] == "#" {
-		if len(domains) > 0 {
-			p.excludeFromReserved(domains)
-
-			return nil
-		}
+	if upstreams[0] == "#" && len(domains) > 0 {
+		p.excludeFromReserved(domains)
 
 		return nil
 	}
@@ -217,7 +219,7 @@ func splitConfigLine(confLine string) (upstreams, domains []string, err error) {
 
 	domainsLine, upstreamsLine, found := strings.Cut(confLine[len("[/"):], "/]")
 	if !found || upstreamsLine == "" {
-		return nil, nil, fmt.Errorf("wrong upstream specification")
+		return nil, nil, errWrongUpstreamSpecs
 	}
 
 	// split domains list