Fix #4139 - escape quoted strings for process start

Author: Nate McMaster

src/Microsoft.DotNet.Cli.Utils/ArgumentEscaper.cs

@@ -185,12 +185,6 @@ private static string EscapeArgForCmd(string argument)
 
         internal static bool ShouldSurroundWithQuotes(string argument)
         {
-            // Don't quote already quoted strings
-            if (IsSurroundedWithQuotes(argument))
-            {
-                return false;
-            }
-
             // Only quote if whitespace exists in the string
             return ArgumentContainsWhitespace(argument);
         }

src/Microsoft.DotNet.Cli.Utils/CommandResolution/WindowsExePreferredCommandSpecFactory.cs

@@ -63,7 +63,8 @@ private CommandSpec CreateCommandSpecWrappedWithCmd(
 
             var cmdEscapedArgs = ArgumentEscaper.EscapeAndConcatenateArgArrayForCmdProcessStart(args);
 
-            if (ArgumentEscaper.ShouldSurroundWithQuotes(command))
+            if (!ArgumentEscaper.IsSurroundedWithQuotes(command) // Don't quote already quoted strings
+                && ArgumentEscaper.ShouldSurroundWithQuotes(command))
             {
                 command = $"\"{command}\"";
             }

test/Microsoft.DotNet.Cli.Utils.Tests/ArgumentEscaperTests.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Xunit;
+
+namespace Microsoft.DotNet.Cli.Utils.Tests
+{
+    public class ArgumentEscaperTests
+    {
+        [Theory]
+        [InlineData(new[] { "one", "two", "three" }, "one two three")]
+        [InlineData(new[] { "line1\nline2", "word1\tword2" }, "\"line1\nline2\" \"word1\tword2\"")]
+        [InlineData(new[] { "with spaces" }, "\"with spaces\"")]
+        [InlineData(new[] { @"with\backslash" }, @"with\backslash")]
+        [InlineData(new[] { @"""quotedwith\backslash""" }, @"\""quotedwith\backslash\""")]
+        [InlineData(new[] { @"C:\Users\" }, @"C:\Users\")]
+        [InlineData(new[] { @"C:\Program Files\dotnet\" }, @"""C:\Program Files\dotnet\\""")]
+        [InlineData(new[] { @"backslash\""preceedingquote" }, @"backslash\\\""preceedingquote")]
+        [InlineData(new[] { @""" hello """ }, @"""\"" hello \""""")]
+        public void EscapesArgumentsForProcessStart(string[] args, string expected)
+        {
+            Assert.Equal(expected, ArgumentEscaper.EscapeAndConcatenateArgArrayForProcessStart(args));
+        }
+    }
+}