No issue - Flag to parse 'v' flag as 'u' for automated tests, disabled by default

js/src/frontend/TokenStream.cpp

@@ -24,6 +24,7 @@
 
 #include "frontend/BytecodeCompiler.h"
 #include "frontend/ReservedWords.h"
+#include "irregexp/FeatureFlags.h"
 #include "js/CharacterEncoding.h"
 #include "js/UniquePtr.h"
 #include "vm/HelperThreads.h"
@@ -1942,6 +1943,8 @@ TokenStream::getTokenInternal(TokenKind* ttp, Modifier modifier)
                     reflags = RegExpFlag(reflags | UnicodeFlag);
                 else if (c == 's' && !(reflags & DotAllFlag))
                     reflags = RegExpFlag(reflags | DotAllFlag);
+                else if (c == 'v' && irregexp::kParseFlagUnicodeSetsAsUnicode && !(reflags & UnicodeFlag))
+                    reflags = RegExpFlag(reflags | UnicodeFlag);
                 else
                     break;
                 getChar();

js/src/irregexp/FeatureFlags.h

@@ -0,0 +1,20 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef irregexp_FeatureFlags_h
+#define irregexp_FeatureFlags_h
+
+namespace js {
+
+namespace irregexp {
+ 
+// Feature flag to treat /../v as /../u   (https://v8.dev/features/regexp-v-flag)
+// We don't support Set Notation or the changed Case Insenstive handling
+// but we have Property Sequences and want them in unit test runs.
+static const bool kParseFlagUnicodeSetsAsUnicode = false;
+
+} } // namespace js::irregexp
+
+#endif // irregexp_FeatureFlags_h

js/src/vm/RegExpObject.cpp

@@ -15,6 +15,7 @@
 
 #include "builtin/RegExp.h"
 #include "frontend/TokenStream.h"
+#include "irregexp/FeatureFlags.h"
 #ifdef DEBUG
 #include "irregexp/RegExpBytecode.h"
 #endif
@@ -1484,6 +1485,13 @@ ParseRegExpFlags(const CharT* chars, size_t length, RegExpFlag* flagsOut, char16
             if (!HandleRegExpFlag(UnicodeFlag, flagsOut))
                 return false;
             break;
+          case 'v':
+            if (irregexp::kParseFlagUnicodeSetsAsUnicode) {
+                if (!HandleRegExpFlag(UnicodeFlag, flagsOut))
+                    return false;
+                break;
+            }
+            MOZ_FALLTHROUGH
           default:
             return false;
         }