fix(execute_code): route CodeDom references through a response file (#1144)

MCPForUnity/Editor/Tools/ExecuteCode.cs

@@ -275,34 +275,57 @@ private static Assembly CodeDomCompile(string source, string[] assemblyPaths, ou
             // CodeDom needs the netstandard-aware filtered paths
             var filtered = FilterAssemblyPathsForCodeDom(assemblyPaths);
 
-            using (var provider = new CSharpCodeProvider())
+            // CSharpCodeProvider turns every ReferencedAssemblies entry into a literal /r:"..." flag
+            // on the csc command line. Projects with ~100+ asmdefs blow past Windows' 32 KB
+            // CreateProcess argument limit and fail with "The filename or extension is too long."
+            // Route references through a response file (@responsefile is supported by both mcs and
+            // Roslyn csc) so we pass exactly one short argument regardless of reference count.
+            string responseFilePath = Path.Combine(Path.GetTempPath(), $"mcp-codedom-{Guid.NewGuid():N}.rsp");
+
+            try
             {
-                var parameters = new CompilerParameters
+                using (var writer = new StreamWriter(responseFilePath, append: false, Encoding.UTF8))
                 {
-                    GenerateInMemory = true,
-                    GenerateExecutable = false,
-                    TreatWarningsAsErrors = false,
-                };
+                    foreach (var path in filtered)
+                    {
+                        writer.Write("/r:\"");
+                        writer.Write(path);
+                        writer.WriteLine("\"");
+                    }
+                }
 
-                foreach (var path in filtered)
-                    parameters.ReferencedAssemblies.Add(path);
+                using (var provider = new CSharpCodeProvider())
+                {
+                    var parameters = new CompilerParameters
+                    {
+                        GenerateInMemory = true,
+                        GenerateExecutable = false,
+                        TreatWarningsAsErrors = false,
+                        CompilerOptions = "@\"" + responseFilePath + "\"",
+                    };
 
-                var results = provider.CompileAssemblyFromSource(parameters, source);
+                    var results = provider.CompileAssemblyFromSource(parameters, source);
 
-                if (results.Errors.HasErrors)
-                {
-                    foreach (CompilerError error in results.Errors)
+                    if (results.Errors.HasErrors)
                     {
-                        if (!error.IsWarning)
+                        foreach (CompilerError error in results.Errors)
                         {
-                            int userLine = Math.Max(1, error.Line - WrapperLineOffset);
-                            errors.Add($"Line {userLine}: {error.ErrorText}");
+                            if (!error.IsWarning)
+                            {
+                                int userLine = Math.Max(1, error.Line - WrapperLineOffset);
+                                errors.Add($"Line {userLine}: {error.ErrorText}");
+                            }
                         }
+                        return null;
                     }
-                    return null;
-                }
 
-                return results.CompiledAssembly;
+                    return results.CompiledAssembly;
+                }
+            }
+            finally
+            {
+                try { if (File.Exists(responseFilePath)) File.Delete(responseFilePath); }
+                catch { /* best effort */ }
             }
         }
 

TestProjects/UnityMCPTests/Assets/Tests/EditMode/Tools/ExecuteCodeTests.cs

@@ -332,6 +332,41 @@ public void NullParams_ReturnsError()
             Assert.IsFalse(result.Value<bool>("success"), result.ToString());
         }
 
+        // ──────────────────── CodeDom backend ────────────────────
+
+        // Regression for CoplayDev/unity-mcp#1144: large projects (~100+ asmdefs) blew past the
+        // Windows 32 KB CreateProcess limit because every reference became an inline /r: flag.
+        // The fix routes references through a @responsefile, so this just verifies that the
+        // codedom path still compiles and runs end-to-end.
+        [Test]
+        public void Execute_CodedomBackend_CompilesAndRuns()
+        {
+            var result = ToJObject(ExecuteCode.HandleCommand(new JObject
+            {
+                ["action"] = "execute",
+                ["code"] = "return 1 + 1;",
+                ["compiler"] = "codedom"
+            }));
+
+            Assert.IsTrue(result.Value<bool>("success"), result.ToString());
+            Assert.AreEqual(2, result["data"]["result"].Value<int>());
+            Assert.AreEqual("codedom", result["data"]["compiler"].Value<string>());
+        }
+
+        [Test]
+        public void Execute_CodedomBackend_ResolvesUnityTypes()
+        {
+            var result = ToJObject(ExecuteCode.HandleCommand(new JObject
+            {
+                ["action"] = "execute",
+                ["code"] = "return UnityEngine.Application.unityVersion;",
+                ["compiler"] = "codedom"
+            }));
+
+            Assert.IsTrue(result.Value<bool>("success"), result.ToString());
+            Assert.IsNotNull(result["data"]["result"]);
+        }
+
         // ──────────────────── Helpers ────────────────────
 
         private static JObject Execute(string code)