Exposed flags to the regex parser

javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java

@@ -600,7 +600,7 @@ public Label visit(Literal nd, Context c) {
         SourceMap sourceMap =
             SourceMap.legacyWithStartPos(
                 SourceMap.fromString(nd.getRaw()).offsetBy(0, offsets), startPos);
-        regexpExtractor.extract(source.substring(1, source.lastIndexOf('/')), sourceMap, nd, false);
+        regexpExtractor.extract(source.substring(1, source.lastIndexOf('/')), sourceMap, nd, false, source.substring(source.lastIndexOf('/'), source.length()));
       } else if (nd.isStringLiteral()
           && !c.isInsideType()
           && nd.getRaw().length() < 1000

javascript/extractor/src/com/semmle/js/extractor/RegExpExtractor.java

@@ -346,8 +346,8 @@ public void visit(CharacterClassRange nd) {
     }
   }
 
-  public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpeculativeParsing) {
-    Result res = parser.parse(src);
+  public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpeculativeParsing, String flags) {
+    Result res = parser.parse(src, flags);
     if (isSpeculativeParsing && res.getErrors().size() > 0) {
       return;
     }
@@ -364,4 +364,8 @@ public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpec
       this.emitLocation(err, lbl);
     }
   }
+
+    public void extract(String src, SourceMap sourceMap, Node parent, boolean isSpeculativeParsing) {
+      extract(src, sourceMap, parent, isSpeculativeParsing, "");
+    }
 }

javascript/extractor/src/com/semmle/js/parser/RegExpParser.java

@@ -67,6 +67,7 @@ public List<Error> getErrors() {
   private List<Error> errors;
   private List<BackReference> backrefs;
   private int maxbackref;
+  private String flags;
 
   /** Parse the given string as a regular expression. */
   public Result parse(String src) {
@@ -82,6 +83,11 @@ public Result parse(String src) {
     return new Result(root, errors);
   }
 
+  public Result parse(String src, String flags) {
+    this.flags = flags;
+    return parse(src);
+  }
+
   private static String fromCodePoint(int codepoint) {
     if (Character.isValidCodePoint(codepoint)) return new String(Character.toChars(codepoint));
     // replacement character