Merge pull request #584 from igotinfected/fix/flaky-codedomprovider-tests

Make calls to CodeDomProvider thread-safe (fixes flaky tests)

Author: mganss

XmlSchemaClassGenerator/Models/ClassModel.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.CodeDom;
 using System.CodeDom.Compiler;
 using System.Collections.Generic;
@@ -345,19 +345,8 @@ public override CodeExpression GetDefaultValueFor(string defaultString, bool att
 
         if (rootClass is SimpleModel || rootClass is EnumModel)
         {
-            string reference, val;
-
-            using (var writer = new System.IO.StringWriter())
-            {
-                CSharpProvider.GenerateCodeFromExpression(rootClass.GetDefaultValueFor(defaultString, attribute), writer, new CodeGeneratorOptions());
-                val = writer.ToString();
-            }
-
-            using (var writer = new System.IO.StringWriter())
-            {
-                CSharpProvider.GenerateCodeFromExpression(new CodeTypeReferenceExpression(GetReferenceFor(referencingNamespace: null)), writer, new CodeGeneratorOptions());
-                reference = writer.ToString();
-            }
+            var val = GenerateCSharpCodeFromExpression(rootClass.GetDefaultValueFor(defaultString, attribute));
+            var reference = GenerateCSharpCodeFromExpression(new CodeTypeReferenceExpression(GetReferenceFor(referencingNamespace: null)));
 
             return new CodeSnippetExpression($"new {reference} {{ {Configuration.TextValuePropertyName} = {val} }};");
         }

XmlSchemaClassGenerator/Models/SimpleModel.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.CodeDom;
 using System.CodeDom.Compiler;
 using System.Collections.Generic;
@@ -45,9 +45,7 @@ private static string GetFullTypeName(string typeName, CodeTypeReference typeRef
         {
             Type = { Options = CodeTypeReferenceOptions.GenericTypeParameter }
         };
-        using var writer = new System.IO.StringWriter();
-        CSharpProvider.GenerateCodeFromExpression(typeOfExpr, writer, new CodeGeneratorOptions());
-        var fullTypeName = writer.ToString();
+        var fullTypeName = GenerateCSharpCodeFromExpression(typeOfExpr);
         Debug.Assert(fullTypeName.StartsWith("typeof(") && fullTypeName.EndsWith(")"), $"Expected typeof expression, got: {fullTypeName}");
         return fullTypeName.Substring(7, fullTypeName.Length - 8);
     }

XmlSchemaClassGenerator/Models/TypeModel.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.CodeDom;
 using System.CodeDom.Compiler;
 using System.Collections.Generic;
@@ -16,7 +16,19 @@ namespace XmlSchemaClassGenerator;
 [DebuggerDisplay("{Name}")]
 public abstract class TypeModel(GeneratorConfiguration configuration) : GeneratorModel(configuration)
 {
-    protected static readonly CodeDomProvider CSharpProvider = CodeDomProvider.CreateProvider("CSharp");
+    private static readonly CodeDomProvider CSharpProvider = CodeDomProvider.CreateProvider("CSharp");
+    private static readonly object CSharpProviderLock = new();
+
+    // prevents simultaneous access to the static CodeDomProvider, which is not thread-safe
+    protected static string GenerateCSharpCodeFromExpression(CodeExpression expression)
+    {
+        lock (CSharpProviderLock)
+        {
+            using var writer = new System.IO.StringWriter();
+            CSharpProvider.GenerateCodeFromExpression(expression, writer, new CodeGeneratorOptions());
+            return writer.ToString();
+        }
+    }
 
     public NamespaceModel Namespace { get; set; }
     public XmlSchemaElement RootElement { get; set; }