vdoc: improve html tag escape (#19266)

cmd/tools/vdoc/html.v

@@ -13,13 +13,16 @@ import v.pref
 import v.util { tabs }
 
 const (
-	css_js_assets         = ['doc.css', 'normalize.css', 'doc.js', 'dark-mode.js']
-	default_theme         = os.resource_abs_path('theme')
-	link_svg              = '<svg xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M3.9 12c0-1.71 1.39-3.1 3.1-3.1h4V7H7c-2.76 0-5 2.24-5 5s2.24 5 5 5h4v-1.9H7c-1.71 0-3.1-1.39-3.1-3.1zM8 13h8v-2H8v2zm9-6h-4v1.9h4c1.71 0 3.1 1.39 3.1 3.1s-1.39 3.1-3.1 3.1h-4V17h4c2.76 0 5-2.24 5-5s-2.24-5-5-5z"/></svg>'
+	css_js_assets               = ['doc.css', 'normalize.css', 'doc.js', 'dark-mode.js']
+	default_theme               = os.resource_abs_path('theme')
+	link_svg                    = '<svg xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M3.9 12c0-1.71 1.39-3.1 3.1-3.1h4V7H7c-2.76 0-5 2.24-5 5s2.24 5 5 5h4v-1.9H7c-1.71 0-3.1-1.39-3.1-3.1zM8 13h8v-2H8v2zm9-6h-4v1.9h4c1.71 0 3.1 1.39 3.1 3.1s-1.39 3.1-3.1 3.1h-4V17h4c2.76 0 5-2.24 5-5s-2.24-5-5-5z"/></svg>'
 
-	single_quote          = "'"
-	double_quote          = '"'
-	no_quotes_replacement = [single_quote, '', double_quote, '']
+	single_quote                = "'"
+	double_quote                = '"'
+	no_quotes_replacement       = [single_quote, '', double_quote, '']
+
+	html_tag_escape_replacement = ['<', '&lt;', '>', '&gt;']
+	html_tag_escape_re          = regex.regex_opt(r'`.+[(&lt;)(&gt;)].+`') or { panic(err) }
 )
 
 enum HighlightTokenTyp {
@@ -450,8 +453,8 @@ fn doc_node_html(dn doc.DocNode, link string, head bool, include_examples bool,
 }
 
 fn html_tag_escape(str string) string {
-	escaped_string := str.replace_each(['<', '&lt;', '>', '&gt;'])
-	mut re := regex.regex_opt(r'`.+[(&lt;)(&gt;)].+`') or { regex.RE{} }
+	escaped_string := str.replace_each(html_tag_escape_replacement)
+	mut re := html_tag_escape_re
 	if re.find_all_str(escaped_string).len > 0 {
 		return str
 	}