add ObjectMethodExecutor

src/DotNetCore.CAP/Internal/ObjectMethodExecutor/AwaitableInfo.cs

+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace Microsoft.Extensions.Internal
+{
+    internal struct AwaitableInfo
+    {
+        public Type AwaiterType { get; }
+        public PropertyInfo AwaiterIsCompletedProperty { get; }
+        public MethodInfo AwaiterGetResultMethod { get; }
+        public MethodInfo AwaiterOnCompletedMethod { get; }
+        public MethodInfo AwaiterUnsafeOnCompletedMethod { get; }
+        public Type ResultType { get; }
+        public MethodInfo GetAwaiterMethod { get; }
+
+        public AwaitableInfo(
+            Type awaiterType,
+            PropertyInfo awaiterIsCompletedProperty,
+            MethodInfo awaiterGetResultMethod,
+            MethodInfo awaiterOnCompletedMethod,
+            MethodInfo awaiterUnsafeOnCompletedMethod,
+            Type resultType,
+            MethodInfo getAwaiterMethod)
+        {
+            AwaiterType = awaiterType;
+            AwaiterIsCompletedProperty = awaiterIsCompletedProperty;
+            AwaiterGetResultMethod = awaiterGetResultMethod;
+            AwaiterOnCompletedMethod = awaiterOnCompletedMethod;
+            AwaiterUnsafeOnCompletedMethod = awaiterUnsafeOnCompletedMethod;
+            ResultType = resultType;
+            GetAwaiterMethod = getAwaiterMethod;
+        }
+
+        public static bool IsTypeAwaitable(Type type, out AwaitableInfo awaitableInfo)
+        {
+            // Based on Roslyn code: http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/Shared/Extensions/ISymbolExtensions.cs,db4d48ba694b9347
+
+            // Awaitable must have method matching "object GetAwaiter()"
+            var getAwaiterMethod = type.GetRuntimeMethods().FirstOrDefault(m =>
+                m.Name.Equals("GetAwaiter", StringComparison.OrdinalIgnoreCase)
+                && m.GetParameters().Length == 0
+                && m.ReturnType != null);
+            if (getAwaiterMethod == null)
+            {
+                awaitableInfo = default(AwaitableInfo);
+                return false;
+            }
+
+            var awaiterType = getAwaiterMethod.ReturnType;
+
+            // Awaiter must have property matching "bool IsCompleted { get; }"
+            var isCompletedProperty = awaiterType.GetRuntimeProperties().FirstOrDefault(p =>
+                p.Name.Equals("IsCompleted", StringComparison.OrdinalIgnoreCase)
+                && p.PropertyType == typeof(bool)
+                && p.GetMethod != null);
+            if (isCompletedProperty == null)
+            {
+                awaitableInfo = default(AwaitableInfo);
+                return false;
+            }
+
+            // Awaiter must implement INotifyCompletion
+            var awaiterInterfaces = awaiterType.GetInterfaces();
+            var implementsINotifyCompletion = awaiterInterfaces.Any(t => t == typeof(INotifyCompletion));
+            if (!implementsINotifyCompletion)
+            {
+                awaitableInfo = default(AwaitableInfo);
+                return false;
+            }
+
+            // INotifyCompletion supplies a method matching "void OnCompleted(Action action)"
+            var iNotifyCompletionMap = awaiterType
+                .GetTypeInfo()
+                .GetRuntimeInterfaceMap(typeof(INotifyCompletion));
+            var onCompletedMethod = iNotifyCompletionMap.InterfaceMethods.Single(m =>
+                m.Name.Equals("OnCompleted", StringComparison.OrdinalIgnoreCase)
+                && m.ReturnType == typeof(void)
+                && m.GetParameters().Length == 1
+                && m.GetParameters()[0].ParameterType == typeof(Action));
+
+            // Awaiter optionally implements ICriticalNotifyCompletion
+            var implementsICriticalNotifyCompletion = awaiterInterfaces.Any(t => t == typeof(ICriticalNotifyCompletion));
+            MethodInfo unsafeOnCompletedMethod;
+            if (implementsICriticalNotifyCompletion)
+            {
+                // ICriticalNotifyCompletion supplies a method matching "void UnsafeOnCompleted(Action action)"
+                var iCriticalNotifyCompletionMap = awaiterType
+                    .GetTypeInfo()
+                    .GetRuntimeInterfaceMap(typeof(ICriticalNotifyCompletion));
+                unsafeOnCompletedMethod = iCriticalNotifyCompletionMap.InterfaceMethods.Single(m =>
+                    m.Name.Equals("UnsafeOnCompleted", StringComparison.OrdinalIgnoreCase)
+                    && m.ReturnType == typeof(void)
+                    && m.GetParameters().Length == 1
+                    && m.GetParameters()[0].ParameterType == typeof(Action));
+            }
+            else
+            {
+                unsafeOnCompletedMethod = null;
+            }
+
+            // Awaiter must have method matching "void GetResult" or "T GetResult()"
+            var getResultMethod = awaiterType.GetRuntimeMethods().FirstOrDefault(m =>
+                m.Name.Equals("GetResult")
+                && m.GetParameters().Length == 0);
+            if (getResultMethod == null)
+            {
+                awaitableInfo = default(AwaitableInfo);
+                return false;
+            }
+
+            awaitableInfo = new AwaitableInfo(
+                awaiterType,
+                isCompletedProperty,
+                getResultMethod,
+                onCompletedMethod,
+                unsafeOnCompletedMethod,
+                getResultMethod.ReturnType,
+                getAwaiterMethod);
+            return true;
+        }
+    }
+}

src/DotNetCore.CAP/Internal/ObjectMethodExecutor/CoercedAwaitableInfo.cs

+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq.Expressions;
+
+namespace Microsoft.Extensions.Internal
+{
+    internal struct CoercedAwaitableInfo
+    {
+        public AwaitableInfo AwaitableInfo { get; }
+        public Expression CoercerExpression { get; }
+        public Type CoercerResultType { get; }
+        public bool RequiresCoercion => CoercerExpression != null;
+
+        public CoercedAwaitableInfo(AwaitableInfo awaitableInfo)
+        {
+            AwaitableInfo = awaitableInfo;
+            CoercerExpression = null;
+            CoercerResultType = null;
+        }
+
+        public CoercedAwaitableInfo(Expression coercerExpression, Type coercerResultType, AwaitableInfo coercedAwaitableInfo)
+        {
+            CoercerExpression = coercerExpression;
+            CoercerResultType = coercerResultType;
+            AwaitableInfo = coercedAwaitableInfo;
+        }
+
+        public static bool IsTypeAwaitable(Type type, out CoercedAwaitableInfo info)
+        {
+            if (AwaitableInfo.IsTypeAwaitable(type, out var directlyAwaitableInfo))
+            {
+                info = new CoercedAwaitableInfo(directlyAwaitableInfo);
+                return true;
+            }
+
+            // It's not directly awaitable, but maybe we can coerce it.
+            // Currently we support coercing FSharpAsync<T>.
+            if (ObjectMethodExecutorFSharpSupport.TryBuildCoercerFromFSharpAsyncToAwaitable(type,
+                out var coercerExpression,
+                out var coercerResultType))
+            {
+                if (AwaitableInfo.IsTypeAwaitable(coercerResultType, out var coercedAwaitableInfo))
+                {
+                    info = new CoercedAwaitableInfo(coercerExpression, coercerResultType, coercedAwaitableInfo);
+                    return true;
+                }
+            }
+
+            info = default(CoercedAwaitableInfo);
+            return false;
+        }
+    }
+}

src/DotNetCore.CAP/Internal/ObjectMethodExecutor/ObjectMethodExecutorAwaitable.cs

+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Microsoft.Extensions.Internal
+{
+    /// <summary>
+    /// Provides a common awaitable structure that <see cref="ObjectMethodExecutor.ExecuteAsync"/> can
+    /// return, regardless of whether the underlying value is a System.Task, an FSharpAsync, or an
+    /// application-defined custom awaitable.
+    /// </summary>
+    internal struct ObjectMethodExecutorAwaitable
+    {
+        private readonly object _customAwaitable;
+        private readonly Func<object, object> _getAwaiterMethod;
+        private readonly Func<object, bool> _isCompletedMethod;
+        private readonly Func<object, object> _getResultMethod;
+        private readonly Action<object, Action> _onCompletedMethod;
+        private readonly Action<object, Action> _unsafeOnCompletedMethod;
+
+        // Perf note: since we're requiring the customAwaitable to be supplied here as an object,
+        // this will trigger a further allocation if it was a value type (i.e., to box it). We can't
+        // fix this by making the customAwaitable type generic, because the calling code typically
+        // does not know the type of the awaitable/awaiter at compile-time anyway.
+        //
+        // However, we could fix it by not passing the customAwaitable here at all, and instead
+        // passing a func that maps directly from the target object (e.g., controller instance),
+        // target method (e.g., action method info), and params array to the custom awaiter in the
+        // GetAwaiter() method below. In effect, by delaying the actual method call until the
+        // upstream code calls GetAwaiter on this ObjectMethodExecutorAwaitable instance.
+        // This optimization is not currently implemented because:
+        // [1] It would make no difference when the awaitable was an object type, which is
+        //     by far the most common scenario (e.g., System.Task<T>).
+        // [2] It would be complex - we'd need some kind of object pool to track all the parameter
+        //     arrays until we needed to use them in GetAwaiter().
+        // We can reconsider this in the future if there's a need to optimize for ValueTask<T>
+        // or other value-typed awaitables.
+
+        public ObjectMethodExecutorAwaitable(
+            object customAwaitable,
+            Func<object, object> getAwaiterMethod,
+            Func<object, bool> isCompletedMethod,
+            Func<object, object> getResultMethod,
+            Action<object, Action> onCompletedMethod,
+            Action<object, Action> unsafeOnCompletedMethod)
+        {
+            _customAwaitable = customAwaitable;
+            _getAwaiterMethod = getAwaiterMethod;
+            _isCompletedMethod = isCompletedMethod;
+            _getResultMethod = getResultMethod;
+            _onCompletedMethod = onCompletedMethod;
+            _unsafeOnCompletedMethod = unsafeOnCompletedMethod;
+        }
+
+        public Awaiter GetAwaiter()
+        {
+            var customAwaiter = _getAwaiterMethod(_customAwaitable);
+            return new Awaiter(customAwaiter, _isCompletedMethod, _getResultMethod, _onCompletedMethod, _unsafeOnCompletedMethod);
+        }
+
+        public struct Awaiter : ICriticalNotifyCompletion
+        {
+            private readonly object _customAwaiter;
+            private readonly Func<object, bool> _isCompletedMethod;
+            private readonly Func<object, object> _getResultMethod;
+            private readonly Action<object, Action> _onCompletedMethod;
+            private readonly Action<object, Action> _unsafeOnCompletedMethod;
+
+            public Awaiter(
+                object customAwaiter,
+                Func<object, bool> isCompletedMethod,
+                Func<object, object> getResultMethod,
+                Action<object, Action> onCompletedMethod,
+                Action<object, Action> unsafeOnCompletedMethod)
+            {
+                _customAwaiter = customAwaiter;
+                _isCompletedMethod = isCompletedMethod;
+                _getResultMethod = getResultMethod;
+                _onCompletedMethod = onCompletedMethod;
+                _unsafeOnCompletedMethod = unsafeOnCompletedMethod;
+            }
+
+            public bool IsCompleted => _isCompletedMethod(_customAwaiter);
+
+            public object GetResult() => _getResultMethod(_customAwaiter);
+
+            public void OnCompleted(Action continuation)
+            {
+                _onCompletedMethod(_customAwaiter, continuation);
+            }
+
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                // If the underlying awaitable implements ICriticalNotifyCompletion, use its UnsafeOnCompleted.
+                // If not, fall back on using its OnCompleted.
+                //
+                // Why this is safe:
+                // - Implementing ICriticalNotifyCompletion is a way of saying the caller can choose whether it
+                //   needs the execution context to be preserved (which it signals by calling OnCompleted), or
+                //   that it doesn't (which it signals by calling UnsafeOnCompleted). Obviously it's faster *not*
+                //   to preserve and restore the context, so we prefer that where possible.
+                // - If a caller doesn't need the execution context to be preserved and hence calls UnsafeOnCompleted,
+                //   there's no harm in preserving it anyway - it's just a bit of wasted cost. That's what will happen
+                //   if a caller sees that the proxy implements ICriticalNotifyCompletion but the proxy chooses to
+                //   pass the call on to the underlying awaitable's OnCompleted method.
+
+                var underlyingMethodToUse = _unsafeOnCompletedMethod ?? _onCompletedMethod;
+                underlyingMethodToUse(_customAwaiter, continuation);
+            }
+        }
+    }
+}
\ No newline at end of file

src/DotNetCore.CAP/Internal/ObjectMethodExecutor/ObjectMethodExecutorFSharpSupport.cs

+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.Extensions.Internal
+{
+    /// <summary>
+    /// Helper for detecting whether a given type is FSharpAsync`1, and if so, supplying
+    /// an <see cref="Expression"/> for mapping instances of that type to a C# awaitable.
+    /// </summary>
+    /// <remarks>
+    /// The main design goal here is to avoid taking a compile-time dependency on
+    /// FSharp.Core.dll, because non-F# applications wouldn't use it. So all the references
+    /// to FSharp types have to be constructed dynamically at runtime.
+    /// </remarks>
+    internal static class ObjectMethodExecutorFSharpSupport
+    {
+        private static object _fsharpValuesCacheLock = new object();
+        private static Assembly _fsharpCoreAssembly;
+        private static MethodInfo _fsharpAsyncStartAsTaskGenericMethod;
+        private static PropertyInfo _fsharpOptionOfTaskCreationOptionsNoneProperty;
+        private static PropertyInfo _fsharpOptionOfCancellationTokenNoneProperty;
+
+        public static bool TryBuildCoercerFromFSharpAsyncToAwaitable(
+            Type possibleFSharpAsyncType,
+            out Expression coerceToAwaitableExpression,
+            out Type awaitableType)
+        {
+            var methodReturnGenericType = possibleFSharpAsyncType.IsGenericType
+                ? possibleFSharpAsyncType.GetGenericTypeDefinition()
+                : null;
+
+            if (!IsFSharpAsyncOpenGenericType(methodReturnGenericType))
+            {
+                coerceToAwaitableExpression = null;
+                awaitableType = null;
+                return false;
+            }
+
+            var awaiterResultType = possibleFSharpAsyncType.GetGenericArguments().Single();
+            awaitableType = typeof(Task<>).MakeGenericType(awaiterResultType);
+
+            // coerceToAwaitableExpression = (object fsharpAsync) =>
+            // {
+            //     return (object)FSharpAsync.StartAsTask<TResult>(
+            //         (Microsoft.FSharp.Control.FSharpAsync<TResult>)fsharpAsync,
+            //         FSharpOption<TaskCreationOptions>.None,
+            //         FSharpOption<CancellationToken>.None);
+            // };
+            var startAsTaskClosedMethod = _fsharpAsyncStartAsTaskGenericMethod
+                .MakeGenericMethod(awaiterResultType);
+            var coerceToAwaitableParam = Expression.Parameter(typeof(object));
+            coerceToAwaitableExpression = Expression.Lambda(
+                Expression.Convert(
+                    Expression.Call(
+                        startAsTaskClosedMethod,
+                        Expression.Convert(coerceToAwaitableParam, possibleFSharpAsyncType),
+                        Expression.MakeMemberAccess(null, _fsharpOptionOfTaskCreationOptionsNoneProperty),
+                        Expression.MakeMemberAccess(null, _fsharpOptionOfCancellationTokenNoneProperty)),
+                    typeof(object)),
+                coerceToAwaitableParam);
+
+            return true;
+        }
+
+        private static bool IsFSharpAsyncOpenGenericType(Type possibleFSharpAsyncGenericType)
+        {
+            var typeFullName = possibleFSharpAsyncGenericType?.FullName;
+            if (!string.Equals(typeFullName, "Microsoft.FSharp.Control.FSharpAsync`1", StringComparison.Ordinal))
+            {
+                return false;
+            }
+
+            lock (_fsharpValuesCacheLock)
+            {
+                if (_fsharpCoreAssembly != null)
+                {
+                    // Since we've already found the real FSharpAsync.Core assembly, we just have
+                    // to check that the supplied FSharpAsync`1 type is the one from that assembly.
+                    return possibleFSharpAsyncGenericType.Assembly == _fsharpCoreAssembly;
+                }
+                else
+                {
+                    // We'll keep trying to find the FSharp types/values each time any type called
+                    // FSharpAsync`1 is supplied.
+                    return TryPopulateFSharpValueCaches(possibleFSharpAsyncGenericType);
+                }
+            }
+        }
+
+        private static bool TryPopulateFSharpValueCaches(Type possibleFSharpAsyncGenericType)
+        {
+            var assembly = possibleFSharpAsyncGenericType.Assembly;
+            var fsharpOptionType = assembly.GetType("Microsoft.FSharp.Core.FSharpOption`1");
+            var fsharpAsyncType = assembly.GetType("Microsoft.FSharp.Control.FSharpAsync");
+
+            if (fsharpOptionType == null || fsharpAsyncType == null)
+            {
+                return false;
+            }
+
+            // Get a reference to FSharpOption<TaskCreationOptions>.None
+            var fsharpOptionOfTaskCreationOptionsType = fsharpOptionType
+                .MakeGenericType(typeof(TaskCreationOptions));
+            _fsharpOptionOfTaskCreationOptionsNoneProperty = fsharpOptionOfTaskCreationOptionsType
+                .GetTypeInfo()
+                .GetRuntimeProperty("None");
+
+            // Get a reference to FSharpOption<CancellationToken>.None
+            var fsharpOptionOfCancellationTokenType = fsharpOptionType
+                .MakeGenericType(typeof(CancellationToken));
+            _fsharpOptionOfCancellationTokenNoneProperty = fsharpOptionOfCancellationTokenType
+                .GetTypeInfo()
+                .GetRuntimeProperty("None");
+
+            // Get a reference to FSharpAsync.StartAsTask<>
+            var fsharpAsyncMethods = fsharpAsyncType
+                .GetRuntimeMethods()
+                .Where(m => m.Name.Equals("StartAsTask", StringComparison.Ordinal));
+            foreach (var candidateMethodInfo in fsharpAsyncMethods)
+            {
+                var parameters = candidateMethodInfo.GetParameters();
+                if (parameters.Length == 3
+                    && TypesHaveSameIdentity(parameters[0].ParameterType, possibleFSharpAsyncGenericType)
+                    && parameters[1].ParameterType == fsharpOptionOfTaskCreationOptionsType
+                    && parameters[2].ParameterType == fsharpOptionOfCancellationTokenType)
+                {
+                    // This really does look like the correct method (and hence assembly).
+                    _fsharpAsyncStartAsTaskGenericMethod = candidateMethodInfo;
+                    _fsharpCoreAssembly = assembly;
+                    break;
+                }
+            }
+
+            return _fsharpCoreAssembly != null;
+        }
+
+        private static bool TypesHaveSameIdentity(Type type1, Type type2)
+        {
+            return type1.Assembly == type2.Assembly
+                && string.Equals(type1.Namespace, type2.Namespace, StringComparison.Ordinal)
+                && string.Equals(type1.Name, type2.Name, StringComparison.Ordinal);
+        }
+    }
+}