Stop escaped compiler args from being mangled by MSBuild

src/Compilers/Core/MSBuildTask/ArgsTaskItem.cs

@@ -0,0 +1,98 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using Microsoft.Build.Framework;
+
+namespace Microsoft.CodeAnalysis.BuildTasks
+{
+    internal sealed class ArgsTaskItem : ITaskItem
+    {
+        // This list is taken from https://github.com/dotnet/msbuild/blob/291a8108761ed347562228f2f8f25477996a5a93/src/Shared/Modifiers.cs#L36-L70
+        private static readonly string[] WellKnownItemSpecMetadataNames =
+        [
+            "FullPath",
+            "RootDir",
+            "Filename",
+            "Extension",
+            "RelativeDir",
+            "Directory",
+            "RecursiveDir",
+            "Identity",
+            "ModifiedTime",
+            "CreatedTime",
+            "AccessedTime",
+            "DefiningProjectFullPath",
+            "DefiningProjectDirectory",
+            "DefiningProjectName",
+            "DefiningProjectExtension",
+        ];
+
+        private readonly Dictionary<string, string> _metadata = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+
+        public ArgsTaskItem(string itemSpec)
+        {
+            ItemSpec = itemSpec;
+        }
+
+        public string ItemSpec { get; set; }
+
+        // Implementation notes that we should include the built-in metadata names as well as our custom ones.
+        public ICollection MetadataNames
+        {
+            get
+            {
+                var clone = new List<string>(_metadata.Keys);
+                clone.AddRange(WellKnownItemSpecMetadataNames);
+                return clone;
+            }
+        }
+
+        // Implementation notes that we should include the built-in metadata names as well as our custom ones.
+        public int MetadataCount => _metadata.Count + WellKnownItemSpecMetadataNames.Length;
+
+        public IDictionary CloneCustomMetadata()
+        {
+            return new Dictionary<string, string>(_metadata, StringComparer.OrdinalIgnoreCase);
+        }
+
+        public void CopyMetadataTo(ITaskItem destinationItem)
+        {
+            // Implementation notes that we should not overwrite existing metadata on the destination.
+            var destinationMetadataNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var name in destinationItem.MetadataNames)
+            {
+                destinationMetadataNames.Add((string)name);
+            }
+
+            foreach (var metadataName in _metadata.Keys)
+            {
+                if (destinationMetadataNames.Contains(metadataName))
+                {
+                    continue;
+                }
+
+                var metadataValue = _metadata[metadataName];
+                destinationItem.SetMetadata(metadataName, metadataValue);
+            }
+        }
+
+        public string GetMetadata(string metadataName)
+        {
+            return _metadata[metadataName];
+        }
+
+        public void RemoveMetadata(string metadataName)
+        {
+            _metadata.Remove(metadataName);
+        }
+
+        public void SetMetadata(string metadataName, string metadataValue)
+        {
+            _metadata[metadataName] = metadataValue;
+        }
+    }
+}

src/Compilers/Core/MSBuildTask/ManagedToolTask.cs

@@ -159,7 +159,7 @@ protected static ITaskItem[] GenerateCommandLineArgsTaskItems(List<string> comma
             var items = new ITaskItem[commandLineArgs.Count];
             for (var i = 0; i < commandLineArgs.Count; i++)
             {
-                items[i] = new TaskItem(commandLineArgs[i]);
+                items[i] = new ArgsTaskItem(commandLineArgs[i]);
             }
 
             return items;

src/Compilers/Core/MSBuildTaskTests/VbcTests.cs

@@ -191,6 +191,19 @@ public void DefineConstantsSimple()
             test("D1 D2");
         }
 
+        [Fact]
+        [WorkItem(72014, "https://github.com/dotnet/roslyn/issues/72014")]
+        public void DefineConstantsWithEscaping()
+        {
+            var vbc = new Vbc();
+            vbc.DefineConstants = "CONFIG=\"DEBUG\"";
+            vbc.Sources = MSBuildUtil.CreateTaskItems("test.vb");
+            var responseFileContents = vbc.GenerateResponseFileContents();
+            var argTaskItems = vbc.GenerateCommandLineArgsTaskItems(responseFileContents);
+            var defineTaskItem = Assert.Single(argTaskItems, item => item.ItemSpec.StartsWith("/define:"));
+            Assert.Equal("/define:\"CONFIG=\\\"DEBUG\\\"\"", defineTaskItem.ItemSpec);
+        }
+
         [Fact]
         public void Features()
         {