Fix regexp syntax error caused by variable names containing any characters except letters, digits, and underscores

regexp.go

@@ -72,13 +72,14 @@ func newRouteRegexp(tpl string, matchHost, matchPrefix, matchQuery, strictSlash
 				tpl[idxs[i]:end])
 		}
 		// Build the regexp pattern.
-		fmt.Fprintf(pattern, "%s(?P<%s>%s)", regexp.QuoteMeta(raw), name, patt)
+		varIdx := i / 2
+		fmt.Fprintf(pattern, "%s(?P<%s>%s)", regexp.QuoteMeta(raw), varGroupName(varIdx), patt)
 		// Build the reverse template.
 		fmt.Fprintf(reverse, "%s%%s", raw)
 
 		// Append variable name and compiled pattern.
-		varsN[i/2] = name
-		varsR[i/2], err = regexp.Compile(fmt.Sprintf("^%s$", patt))
+		varsN[varIdx] = name
+		varsR[varIdx], err = regexp.Compile(fmt.Sprintf("^%s$", patt))
 		if err != nil {
 			return nil, err
 		}
@@ -224,6 +225,11 @@ func braceIndices(s string) ([]int, error) {
 	return idxs, nil
 }
 
+// varGroupName builds a capturing group name for the indexed variable.
+func varGroupName(idx int) string {
+	return fmt.Sprintf("v%d", idx)
+}
+
 // ----------------------------------------------------------------------------
 // routeRegexpGroup
 // ----------------------------------------------------------------------------
@@ -244,8 +250,8 @@ func (v *routeRegexpGroup) setMatch(req *http.Request, m *RouteMatch, r *Route)
 			subexpNames := v.host.regexp.SubexpNames()
 			varName := 0
 			for i, name := range subexpNames[1:] {
-				if name != "" && v.host.varsN[varName] == name {
-					m.Vars[name] = hostVars[i+1]
+				if name == varGroupName(varName) {
+					m.Vars[v.host.varsN[varName]] = hostVars[i+1]
 					varName++
 				}
 			}
@@ -258,8 +264,8 @@ func (v *routeRegexpGroup) setMatch(req *http.Request, m *RouteMatch, r *Route)
 			subexpNames := v.path.regexp.SubexpNames()
 			varName := 0
 			for i, name := range subexpNames[1:] {
-				if name != "" && v.path.varsN[varName] == name {
-					m.Vars[name] = pathVars[i+1]
+				if name == varGroupName(varName) {
+					m.Vars[v.path.varsN[varName]] = pathVars[i+1]
 					varName++
 				}
 			}
@@ -286,8 +292,8 @@ func (v *routeRegexpGroup) setMatch(req *http.Request, m *RouteMatch, r *Route)
 			subexpNames := q.regexp.SubexpNames()
 			varName := 0
 			for i, name := range subexpNames[1:] {
-				if name != "" && q.varsN[varName] == name {
-					m.Vars[name] = queryVars[i+1]
+				if name == varGroupName(varName) {
+					m.Vars[q.varsN[varName]] = queryVars[i+1]
 					varName++
 				}
 			}