Allow RegexOptions.NonBacktracking as 'l' flag

Author: ieviev

src/fable-library-ts/RegExp.ts

@@ -7,11 +7,16 @@ export function create(pattern: string, options = 0) {
   // * Compiled:    0x0008 (ignored)
   // * Singleline:  0x0010
   // * ECMAScript:  0x0100 (ignored)
-  if ((options & ~(1 ^ 2 ^ 8 ^ 16 ^ 256)) !== 0) {
-    throw new Error("RegexOptions only supports: IgnoreCase, Multiline, Compiled, Singleline and ECMAScript");
+  // * NonBacktracking:  0x0400
+  if ((options & ~(1 ^ 2 ^ 8 ^ 16 ^ 256 ^ 1024)) !== 0) {
+    throw new Error("RegexOptions only supports: IgnoreCase, Multiline, Compiled, Singleline, ECMAScript and NonBacktracking");
   }
-  // Set always global and unicode flags for compatibility with dotnet, see #2925
-  let flags = "gu";
+
+  let flags = "";
+  // Set global and unicode flags for compatibility with dotnet, see #2925
+  // for NonBacktracking, add just 'l', ('u' + 'l' is unsupported, 'g' + 'l'
+  // is supported only with '--enable-experimental-regexp-engine')
+  flags += options & 1024 ? "l" : "gu";
   flags += options & 1 ? "i" : ""; // 0x0001 RegexOptions.IgnoreCase
   flags += options & 2 ? "m" : "";
   flags += options & 16 ? "s" : "";

tests/Js/Main/RegexTests.fs

@@ -37,6 +37,32 @@ let tests =
         let r = Regex("[a-z]", options)
         int r.Options |> equal 257
 
+    testCase "RegexOptions.NonBacktracking = 1024" <| fun _ ->
+        let options = RegexOptions.NonBacktracking
+        int options |> equal 1024
+
+    // these tests depend on '--enable-experimental-regexp-engine' or
+    // an newer version of V8 that supports 'l' flag
+    // the tests are ascii only, 'l' and 'u' together are not supported
+    // testCase "Nonbacktracking regex tests" <| fun _ ->
+        // let none = RegexOptions.None
+        // let nonb = RegexOptions.NonBacktracking
+        // let multiline = RegexOptions.Multiline
+        // let ignorecase = RegexOptions.IgnoreCase
+        // let multilineignorecase = multiline ||| ignorecase
+        // let str = "For more information, see Chapter 3.4.5.1"
+        // let sameResult extraopts str pat =
+        //     let result1 = Regex.Match(str, pat, none ||| extraopts).Success
+        //     let result2 = Regex.Match(str, pat, nonb ||| extraopts).Success
+        //     equal result1 result2
+        // sameResult none str "Chapter \d+(\.\d)*"
+        // sameResult none str "chapter \d+(\.\d)*"
+        // sameResult multilineignorecase "^ab" "ab\ncd"
+        // sameResult multilineignorecase "^cd" "ab\ncd"
+        // sameResult multilineignorecase "^AB" "ab\ncd"
+        // sameResult multilineignorecase "^bc" "ab\ncd"
+
+
     testCase "Regex.IsMatch with IgnoreCase and Multiline works" <| fun _ ->
         let str = "ab\ncd"
         let option1 = RegexOptions.IgnoreCase