Preserve v prefix for Go versions

constraint.go

@@ -19,24 +19,39 @@ type Constraint struct {
 
 // ParseConstraint parses a constraint string into a Constraint.
 func ParseConstraint(s string) (*Constraint, error) {
+	return parseConstraintWithScheme(s, "")
+}
+
+// parseConstraintWithScheme parses a constraint with scheme-specific handling.
+// For Go/golang schemes, the v prefix is preserved.
+func parseConstraintWithScheme(s, scheme string) (*Constraint, error) {
 	s = strings.TrimSpace(s)
 	if s == "" {
 		return nil, fmt.Errorf("empty constraint")
 	}
 
+	// Go versions preserve the v prefix
+	preserveVPrefix := scheme == "go" || scheme == "golang"
+
 	matches := operatorRegex.FindStringSubmatch(s)
 	if matches != nil {
 		operator := matches[1]
 		version := strings.TrimSpace(s[len(operator):])
 		if version == "" {
 			return nil, fmt.Errorf("invalid constraint format: %s", s)
 		}
-		version = stripVPrefix(version)
+		if !preserveVPrefix {
+			version = stripVPrefix(version)
+		}
 		return &Constraint{Operator: operator, Version: version}, nil
 	}
 
 	// No operator found, treat as exact match
-	return &Constraint{Operator: "=", Version: stripVPrefix(s)}, nil
+	version := s
+	if !preserveVPrefix {
+		version = stripVPrefix(s)
+	}
+	return &Constraint{Operator: "=", Version: version}, nil
 }
 
 // stripVPrefix removes a leading 'v' or 'V' from version strings.

parser.go

@@ -181,7 +181,7 @@ func (p *Parser) parseConstraints(constraintsStr, scheme string) (*Range, error)
 			continue
 		}
 
-		constraint, err := ParseConstraint(part)
+		constraint, err := parseConstraintWithScheme(part, scheme)
 		if err != nil {
 			return nil, err
 		}
@@ -630,7 +630,7 @@ func (p *Parser) parseGoRange(s string) (*Range, error) {
 		parts := strings.Split(s, ",")
 		var result *Range
 		for _, part := range parts {
-			constraint, err := ParseConstraint(strings.TrimSpace(part))
+			constraint, err := parseConstraintWithScheme(strings.TrimSpace(part), "go")
 			if err != nil {
 				return nil, err
 			}