From 1400e3cf58c14594f06d98db25e10f908480ce67 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Fri, 30 Jul 2021 09:41:41 -0400
Subject: [PATCH] LibRegex: Allow separately parsing patterns and creating
 Regex objects

Adds a static method to parse a regex pattern and return the result, and
a constructor to accept a parse result. This is to allow LibJS to parse
the pattern string of a RegExpLiteral once and hand off regex objects
any number of times thereafter.
---
 Userland/Libraries/LibRegex/RegexMatcher.cpp | 18 ++++++++++++++++++
 Userland/Libraries/LibRegex/RegexMatcher.h   |  3 +++
 2 files changed, 21 insertions(+)

diff --git a/Userland/Libraries/LibRegex/RegexMatcher.cpp b/Userland/Libraries/LibRegex/RegexMatcher.cpp
index bd9680d41a..e30d285716 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.cpp
+++ b/Userland/Libraries/LibRegex/RegexMatcher.cpp
@@ -18,6 +18,15 @@ namespace regex {
 static RegexDebug s_regex_dbg(stderr);
 #endif
 
+template<class Parser>
+regex::Parser::Result Regex<Parser>::parse_pattern(StringView pattern, typename ParserTraits<Parser>::OptionsType regex_options)
+{
+    regex::Lexer lexer(pattern);
+
+    Parser parser(lexer, regex_options);
+    return parser.parse();
+}
+
 template<class Parser>
 Regex<Parser>::Regex(String pattern, typename ParserTraits<Parser>::OptionsType regex_options)
     : pattern_value(move(pattern))
@@ -31,6 +40,15 @@ Regex<Parser>::Regex(String pattern, typename ParserTraits<Parser>::OptionsType
         matcher = make<Matcher<Parser>>(this, regex_options);
 }
 
+template<class Parser>
+Regex<Parser>::Regex(regex::Parser::Result parse_result, String pattern, typename ParserTraits<Parser>::OptionsType regex_options)
+    : pattern_value(move(pattern))
+    , parser_result(move(parse_result))
+{
+    if (parser_result.error == regex::Error::NoError)
+        matcher = make<Matcher<Parser>>(this, regex_options);
+}
+
 template<class Parser>
 Regex<Parser>::Regex(Regex&& regex)
     : pattern_value(move(regex.pattern_value))
diff --git a/Userland/Libraries/LibRegex/RegexMatcher.h b/Userland/Libraries/LibRegex/RegexMatcher.h
index 35e72962ce..1229bacc94 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.h
+++ b/Userland/Libraries/LibRegex/RegexMatcher.h
@@ -80,7 +80,10 @@ public:
     OwnPtr<Matcher<Parser>> matcher { nullptr };
     mutable size_t start_offset { 0 };
 
+    static regex::Parser::Result parse_pattern(StringView pattern, typename ParserTraits<Parser>::OptionsType regex_options = {});
+
     explicit Regex(String pattern, typename ParserTraits<Parser>::OptionsType regex_options = {});
+    Regex(regex::Parser::Result parse_result, String pattern, typename ParserTraits<Parser>::OptionsType regex_options = {});
     ~Regex() = default;
     Regex(Regex&&);
     Regex& operator=(Regex&&);