From f86ee5a6c2840795dcc6ea1b84ecf02e383bdec0 Mon Sep 17 00:00:00 2001
From: zhengchun <zhengchunster@gmail.com>
Date: Thu, 26 Oct 2023 13:34:16 +0800
Subject: [PATCH] fix #92

---
 build.go      |  6 ++++++
 xpath_test.go | 10 ++++++++++
 2 files changed, 16 insertions(+)

diff --git a/build.go b/build.go
index ff494f1..2977bbc 100644
--- a/build.go
+++ b/build.go
@@ -218,6 +218,12 @@ func (b *builder) processFunctionNode(root *functionNode) (query, error) {
 		if arg2, err = b.processNode(root.Args[1]); err != nil {
 			return nil, err
 		}
+		// Issue #92, testing the regular expression before.
+		if q, ok := arg2.(*constantQuery); ok {
+			if _, err = getRegexp(q.Val.(string)); err != nil {
+				return nil, fmt.Errorf("matches() got error. %v", err)
+			}
+		}
 		qyOutput = &functionQuery{Input: b.firstInput, Func: matchesFunc(arg1, arg2)}
 	case "substring":
 		//substring( string , start [, length] )
diff --git a/xpath_test.go b/xpath_test.go
index d87a0e0..7441d33 100644
--- a/xpath_test.go
+++ b/xpath_test.go
@@ -360,6 +360,16 @@ func TestFunction(t *testing.T) {
 	testXPath3(t, html, "//li/preceding::*[1]", selectNode(html, "//h1"))
 }
 
+func TestFunction_matches(t *testing.T) {
+	// testing unexpected the regular expression.
+	if _, err := build(`//*[matches(., '^[\u0621-\u064AA-Za-z\-]+')]`, nil); err == nil {
+		t.Fatal("matches() should got error, but nil")
+	}
+	if _, err := build(`//*[matches(., '//*[matches(., '\w+`, nil); err == nil {
+		t.Fatal("matches() should got error, but nil")
+	}
+}
+
 func TestTransformFunctionReverse(t *testing.T) {
 	nodes := selectNodes(html, "reverse(//li)")
 	expectedReversedNodeValues := []string{"", "login", "about", "Home"}