Add ConvertFrom(Regex) support

Author: RenderMichael

dotnet/src/webdriver/BiDi/Modules/Script/LocalValue.cs

@@ -23,6 +23,7 @@
 using System.Linq;
 using System.Numerics;
 using System.Text.Json.Serialization;
+using System.Text.RegularExpressions;
 
 namespace OpenQA.Selenium.BiDi.Modules.Script;
 
@@ -79,6 +80,9 @@ public static LocalValue ConvertFrom(object? value)
             case string str:
                 return ConvertFrom(str);
 
+            case Regex regex:
+                return ConvertFrom(regex);
+
             case { } when value.GetType().GetInterfaces()
                 .Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(ISet<>)):
                 {
@@ -155,6 +159,27 @@ public static LocalValue ConvertFrom(string? value)
         return new NullLocalValue();
     }
 
+    /// <summary>
+    /// Converts a .NET Regex into a BiDi Regex
+    /// </summary>
+    /// <param name="regex">A .NET Regex.</param>
+    /// <returns>A BiDi Regex.</returns>
+    /// <remarks>
+    /// Note that the .NET regular expression engine does not work the same as the JavaScript engine.
+    /// To minimize the differences between the two engines, it is recommended to enabled the <see cref="RegexOptions.ECMAScript"/> option.
+    /// </remarks>
+    public static LocalValue ConvertFrom(Regex? regex)
+    {
+        if (regex is null)
+        {
+            return new NullLocalValue();
+        }
+
+        string? flags = RegExpValue.GetRegExpFlags(regex.Options);
+
+        return new RegExpLocalValue(new RegExpValue(regex.ToString()) { Flags = flags });
+    }
+
     public static LocalValue ConvertFrom(DateTime? value)
     {
         if (value is null)

dotnet/src/webdriver/BiDi/Modules/Script/RegExpValue.cs

@@ -17,9 +17,62 @@
 // under the License.
 // </copyright>
 
+using System;
+using System.Diagnostics;
+using System.Text.RegularExpressions;
+
 namespace OpenQA.Selenium.BiDi.Modules.Script;
 
 public record RegExpValue(string Pattern)
 {
     public string? Flags { get; set; }
+
+    internal static string? GetRegExpFlags(RegexOptions options)
+    {
+        if (options == RegexOptions.None)
+        {
+            return null;
+        }
+
+        string flags = string.Empty;
+        const RegexOptions NonBacktracking = (RegexOptions)1024;
+#if NET8_0_OR_GREATER
+        Debug.Assert(NonBacktracking == RegexOptions.NonBacktracking);
+#endif
+        const RegexOptions NonApplicableOptions = RegexOptions.Compiled | NonBacktracking;
+
+        const RegexOptions UnsupportedOptions =
+            RegexOptions.ExplicitCapture |
+            RegexOptions.IgnorePatternWhitespace |
+            RegexOptions.RightToLeft |
+            RegexOptions.CultureInvariant;
+
+        options &= ~NonApplicableOptions;
+        if ((options & UnsupportedOptions) != 0)
+        {
+            throw new NotSupportedException($"The selected RegEx options are not supported in BiDi: {options & UnsupportedOptions}");
+        }
+
+        if ((options & RegexOptions.IgnoreCase) != 0)
+        {
+            flags += "i";
+            options = options & ~RegexOptions.IgnoreCase;
+        }
+
+        if ((options & RegexOptions.Multiline) != 0)
+        {
+            options = options & ~RegexOptions.Multiline;
+            flags += "m";
+        }
+
+        if ((options & RegexOptions.Singleline) != 0)
+        {
+            options = options & ~RegexOptions.Singleline;
+            flags += "s";
+        }
+
+        Debug.Assert(options == RegexOptions.None);
+
+        return flags;
+    }
 }