#12: Add support for shimming async methods

README.md

@@ -1,11 +1,13 @@
-[![Build status](https://dev.azure.com/palmund/Pose/_apis/build/status/Pose-CI?branchName=master)](https://dev.azure.com/palmund/Pose/_build/latest?definitionId=12)
-[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
-[![NuGet version](https://badge.fury.io/nu/Poser.svg)](https://www.nuget.org/packages/Poser)
-# Pose
+[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](LICENSE)
+[![Build status](https://dev.azure.com/palmund/Pose/_apis/build/status/Pose-CI?branchName=master&Label=build)](https://dev.azure.com/palmund/Pose/_build/latest?definitionId=12)
+[![NuGet version](https://img.shields.io/nuget/v/Poser?logo=nuget)](https://www.nuget.org/packages/Poser)
+[![NuGet preview version](https://img.shields.io/nuget/vpre/Poser?logo=nuget)](https://www.nuget.org/packages/Poser)
 
-Pose allows you to replace any .NET method (including static and non-virtual) with a delegate. It is similar to [Microsoft Fakes](https://msdn.microsoft.com/en-us/library/hh549175.aspx) but unlike it Pose is implemented _entirely_ in managed code (Reflection Emit API). Everything occurs at runtime and in-memory, no unmanaged Profiling APIs and no file system pollution with re-written assemblies.
+# Poser
 
-Pose is cross platform and runs anywhere .NET is supported. It targets .NET Standard 2.0 so it can be used across .NET platforms including .NET Framework, .NET Core, Mono and Xamarin. See version compatibility table [here](https://docs.microsoft.com/en-us/dotnet/standard/net-standard).
+Poser allows you to replace any .NET method (including static and non-virtual) with a delegate. It is similar to [Microsoft Fakes](https://msdn.microsoft.com/en-us/library/hh549175.aspx) but unlike it Poser is implemented _entirely_ in managed code (Reflection Emit API). Everything occurs at runtime and in-memory, no unmanaged Profiling APIs and no file system pollution with re-written assemblies.
+
+Poser is cross platform and runs anywhere .NET is supported. It targets .NET Standard 2.0 so it can be used across .NET platforms including .NET Framework, .NET Core, Mono and Xamarin. See version compatibility table [here](https://docs.microsoft.com/en-us/dotnet/standard/net-standard).
 
 ## Installation
 
@@ -14,18 +16,18 @@ Available on [NuGet](https://www.nuget.org/packages/Poser/)
 Visual Studio:
 
 ```powershell
-PM> Install-Package Pose
+PM> Install-Package Poser
 ```
 
 .NET Core CLI:
 
 ```bash
-dotnet add package Pose
+dotnet add package Poser
 ```
 
 ## Usage
 
-Pose gives you the ability to create shims by way of the `Shim` class. Shims are basically objects that let you specify the method you want to replace as well as the replacement delegate. Delegate signatures (arguments and return type) must match that of the methods they replace. The `Is` class is used to create instances of a type and all code you want to apply your shims to is isolated using the `PoseContext` class.
+Poser gives you the ability to create shims by way of the `Shim` class. Shims are basically objects that let you specify the method you want to replace as well as the replacement delegate. Delegate signatures (arguments and return type) must match that of the methods they replace. The `Is` class is used to create instances of a type and all code you want to apply your shims to is isolated using the `PoseContext` class.
 
 
 ### Shim static method
@@ -139,14 +141,74 @@ PoseContext.Isolate(() =>
 }, consoleShim, dateTimeShim, classPropShim, classShim, myClassShim, structShim);
 ```
 
+## Async usage
+### Shim static async method
+```csharp
+using Pose;
+
+Shim staticTaskShim = Shim.Replace(() => DoWorkAsync()).With(
+    delegate
+    {
+        Console.Write("refusing to do work");
+        return Task.CompletedTask;
+    });
+```
+
+### Shim async instance method of a Reference Type
+```csharp
+using Pose;
+
+Shim instanceTaskShim = Shim.Replace(() => Is.A<MyClass>().DoSomethingAsync()).With(
+    delegate(MyClass @this)
+    {
+        Console.WriteLine("doing something else async");
+        return Task.CompletedTask;
+    });
+```
+
+### Shim method of specific instance of a Reference Type
+_Not supported for now. When supported, however, it will look like the following._
+
+```csharp
+using Pose;
+
+MyClass myClass = new MyClass();
+Shim myClassTaskShim = Shim.Replace(() => myClass.DoSomethingAsync()).With(
+    delegate(MyClass @this)
+    {
+        Console.WriteLine("doing something else with myClass async");
+        return Task.CompletedTask;
+    });
+```
+
+### Isolating your async code
+
+```csharp
+// This block executes immediately
+await PoseContext.Isolate(async () =>
+{
+    // All code that executes within this block
+    // is isolated and shimmed methods are replaced
+
+    // Outputs "refusing to do work"
+    await DoWorkAsync();
+
+    // Outputs "doing something else async"
+    new MyClass().DoSomethingAsync();
+
+    // Outputs "doing something else with myClass async"
+    await myClass.DoSomethingAsync();
+
+}, staticTaskShim, instanceTaskShim, myClassTaskShim);
+```
 ## Caveats & Limitations
 
 * **Breakpoints** - At this time any breakpoints set anywhere in the isolated code and its execution path will not be hit. However, breakpoints set within a shim replacement delegate are hit.
 * **Exceptions** - At this time all unhandled exceptions thrown in isolated code and its execution path are always wrapped in `System.Reflection.TargetInvocationException`.
 
 ## Roadmap
 
-* **Performance Improvements** - Pose can be used outside the context of unit tests. Better performance would make it suitable for use in production code, possibly to override legacy functionality.
+* **Performance Improvements** - Poser can be used outside the context of unit tests. Better performance would make it suitable for use in production code, possibly to override legacy functionality.
 * **Exceptions Stack Trace** - Currently when exceptions are thrown in your own code under isolation, the supplied exception stack trace is quite confusing. Providing an undiluted exception stack trace is needed.
 
 ## Issues & Contributions

nuget/Poser.nuspec

@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
   <metadata>
     <id>Poser</id>
-    <version>2.0.0</version>
+    <version>2.0.1</version>
     <title>Pose</title>
     <authors>Søren Guldmund</authors>
     <owners>Søren Guldmund</owners>
@@ -16,7 +16,7 @@
     <copyright>Copyright 2024</copyright>
 	  <readme>docs\README.md</readme>
     <releaseNotes>
-      Provide better exception message when we cannot create instance.
+      Fix bug where `Enum.IsDefined` could not be called from within `PoseContext.Isolate`.
 	  </releaseNotes>
 
     <dependencies>

src/Pose/Extensions/TypeExtensions.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace Pose.Extensions
+{
+    internal static class TypeExtensions
+    {
+        public static bool ImplementsInterface<TInterface>(this Type type)
+        {
+            if (type == null) throw new ArgumentNullException(nameof(type));
+            if (!typeof(TInterface).IsInterface) throw new InvalidOperationException($"{typeof(TInterface)} is not an interface.");
+
+            return type.GetInterfaces().Any(interfaceType => interfaceType == typeof(TInterface));
+        }
+
+        public static bool HasAttribute<TAttribute>(this Type type) where TAttribute : Attribute
+        {
+            if (type == null) throw new ArgumentNullException(nameof(type));
+
+            var compilerGeneratedAttribute = type.GetCustomAttribute<TAttribute>() ?? type.ReflectedType?.GetCustomAttribute<TAttribute>();
+
+            return compilerGeneratedAttribute != null;
+        }
+
+        public static MethodInfo GetExplicitlyImplementedMethod<TInterface>(this Type type, string methodName)
+        {
+            if (type == null) throw new ArgumentNullException(nameof(type));
+            if (string.IsNullOrWhiteSpace(methodName)) throw new ArgumentException("Value cannot be null or whitespace.", nameof(methodName));
+
+            var interfaceType = type.GetInterfaceType<TInterface>() ?? throw new Exception();
+            var method = interfaceType.GetMethod(methodName) ?? throw new Exception();
+            var methodDeclaringType = method.DeclaringType ?? throw new Exception($"The {methodName} method does not have a declaring type");
+            var interfaceMapping = type.GetInterfaceMap(methodDeclaringType);
+            var requestedTargetMethod = interfaceMapping.TargetMethods.FirstOrDefault(m => m.Name == methodName);
+
+            return requestedTargetMethod;
+        }
+
+        private static Type GetInterfaceType<TInterface>(this Type type)
+        {
+            if (type == null) throw new ArgumentNullException(nameof(type));
+            if (!typeof(TInterface).IsInterface) throw new InvalidOperationException($"{typeof(TInterface)} is not an interface.");
+
+            return type.GetInterfaces().FirstOrDefault(interfaceType => interfaceType == typeof(TInterface));
+        }
+
+        public static bool IsAsync(this Type thisType)
+        {
+            if (thisType == null) throw new ArgumentNullException(nameof(thisType));
+
+            return
+                // State machines are generated by the compiler...
+                thisType.HasAttribute<CompilerGeneratedAttribute>()
+
+                // as nested private classes...
+                && thisType.IsNestedPrivate
+
+                // which implements IAsyncStateMachine. 
+                && thisType.ImplementsInterface<IAsyncStateMachine>();
+        }
+    }
+}

src/Pose/Helpers/StubHelper.cs

@@ -2,7 +2,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Emit;
-
+using System.Runtime.CompilerServices;
 using Pose.Extensions;
 
 namespace Pose.Helpers
@@ -58,6 +58,11 @@ public static MethodInfo DeVirtualizeMethod(Type thisType, MethodInfo virtualMet
 
             var bindingFlags = BindingFlags.Instance | (virtualMethod.IsPublic ? BindingFlags.Public : BindingFlags.NonPublic);
             var types = virtualMethod.GetParameters().Select(p => p.ParameterType).ToArray();
+
+            if (thisType.IsAsync())
+            {
+                return thisType.GetExplicitlyImplementedMethod<IAsyncStateMachine>(nameof(IAsyncStateMachine.MoveNext));
+            }
 
             return thisType.GetMethod(virtualMethod.Name, bindingFlags, null, types, null);
         }
@@ -94,11 +99,7 @@ public static string CreateStubNameFromMethod(string prefix, MethodBase method)
                 if (genericArguments.Length > 0)
                 {
                     name += "[";
-#if NETSTANDARD2_1_OR_GREATER
-                    name += string.Join(',', genericArguments.Select(g => g.Name));
-#else
                     name += string.Join(",", genericArguments.Select(g => g.Name));
-#endif
                     name += "]";
                 }
             }