private ObjectMethodExecutor(MethodInfo methodInfo, TypeInfo targetTypeInfo, object?[]?parameterDefaultValues)
{
if (methodInfo == null)
{
throw new ArgumentNullException(nameof(methodInfo));
}
MethodInfo = methodInfo;
MethodParameters = methodInfo.GetParameters();
TargetTypeInfo = targetTypeInfo;
MethodReturnType = methodInfo.ReturnType;
var isAwaitable = CoercedAwaitableInfo.IsTypeAwaitable(MethodReturnType, out var coercedAwaitableInfo);
IsMethodAsync = isAwaitable;
AsyncResultType = isAwaitable ? coercedAwaitableInfo.AwaitableInfo.ResultType : null;
// Upstream code may prefer to use the sync-executor even for async methods, because if it knows
// that the result is a specific Task<T> where T is known, then it can directly cast to that type
// and await it without the extra heap allocations involved in the _executorAsync code path.
_executor = GetExecutor(methodInfo, targetTypeInfo);
if (IsMethodAsync)
{
_executorAsync = GetExecutorAsync(methodInfo, targetTypeInfo, coercedAwaitableInfo);
}
_parameterDefaultValues = parameterDefaultValues;
}
public static bool IsTypeAwaitable(Type type, out CoercedAwaitableInfo info)
{
if (AwaitableInfo.IsTypeAwaitable(type, out var directlyAwaitableInfo))
{
info = new CoercedAwaitableInfo(directlyAwaitableInfo);
return(true);
}
info = default(CoercedAwaitableInfo);
return(false);
}
private static MethodExecutorAsync GetExecutorAsync(
MethodInfo methodInfo,
TypeInfo targetTypeInfo,
CoercedAwaitableInfo coercedAwaitableInfo)
{
// Parameters to executor
var targetParameter = Expression.Parameter(typeof(object), "target");
var parametersParameter = Expression.Parameter(typeof(object[]), "parameters");
// Build parameter list
var paramInfos = methodInfo.GetParameters();
var parameters = new List <Expression>(paramInfos.Length);
for (int i = 0; i < paramInfos.Length; i++)
{
var paramInfo = paramInfos[i];
var valueObj = Expression.ArrayIndex(parametersParameter, Expression.Constant(i));
var valueCast = Expression.Convert(valueObj, paramInfo.ParameterType);
// valueCast is "(Ti) parameters[i]"
parameters.Add(valueCast);
}
// Call method
var instanceCast = Expression.Convert(targetParameter, targetTypeInfo.AsType());
var methodCall = Expression.Call(instanceCast, methodInfo, parameters);
// Using the method return value, construct an ObjectMethodExecutorAwaitable based on
// the info we have about its implementation of the awaitable pattern. Note that all
// the funcs/actions we construct here are precompiled, so that only one instance of
// each is preserved throughout the lifetime of the ObjectMethodExecutor.
// var getAwaiterFunc = (object awaitable) =>
// (object)((CustomAwaitableType)awaitable).GetAwaiter();
var customAwaitableParam = Expression.Parameter(typeof(object), "awaitable");
var awaitableInfo = coercedAwaitableInfo.AwaitableInfo;
var postCoercionMethodReturnType = coercedAwaitableInfo.CoercerResultType ?? methodInfo.ReturnType;
var getAwaiterFunc = Expression.Lambda <Func <object, object> >(
Expression.Convert(
Expression.Call(
Expression.Convert(customAwaitableParam, postCoercionMethodReturnType),
awaitableInfo.GetAwaiterMethod),
typeof(object)),
customAwaitableParam).Compile();
// var isCompletedFunc = (object awaiter) =>
// ((CustomAwaiterType)awaiter).IsCompleted;
var isCompletedParam = Expression.Parameter(typeof(object), "awaiter");
var isCompletedFunc = Expression.Lambda <Func <object, bool> >(
Expression.MakeMemberAccess(
Expression.Convert(isCompletedParam, awaitableInfo.AwaiterType),
awaitableInfo.AwaiterIsCompletedProperty),
isCompletedParam).Compile();
var getResultParam = Expression.Parameter(typeof(object), "awaiter");
Func <object, object> getResultFunc;
if (awaitableInfo.ResultType == typeof(void))
{
// var getResultFunc = (object awaiter) =>
// {
// ((CustomAwaiterType)awaiter).GetResult(); // We need to invoke this to surface any exceptions
// return (object)null;
// };
getResultFunc = Expression.Lambda <Func <object, object> >(
Expression.Block(
Expression.Call(
Expression.Convert(getResultParam, awaitableInfo.AwaiterType),
awaitableInfo.AwaiterGetResultMethod),
Expression.Constant(null)
),
getResultParam).Compile();
}
else
{
// var getResultFunc = (object awaiter) =>
// (object)((CustomAwaiterType)awaiter).GetResult();
getResultFunc = Expression.Lambda <Func <object, object> >(
Expression.Convert(
Expression.Call(
Expression.Convert(getResultParam, awaitableInfo.AwaiterType),
awaitableInfo.AwaiterGetResultMethod),
typeof(object)),
getResultParam).Compile();
}
// var onCompletedFunc = (object awaiter, Action continuation) => {
// ((CustomAwaiterType)awaiter).OnCompleted(continuation);
// };
var onCompletedParam1 = Expression.Parameter(typeof(object), "awaiter");
var onCompletedParam2 = Expression.Parameter(typeof(Action), "continuation");
var onCompletedFunc = Expression.Lambda <Action <object, Action> >(
Expression.Call(
Expression.Convert(onCompletedParam1, awaitableInfo.AwaiterType),
awaitableInfo.AwaiterOnCompletedMethod,
onCompletedParam2),
onCompletedParam1,
onCompletedParam2).Compile();
Action <object, Action>?unsafeOnCompletedFunc = null;
if (awaitableInfo.AwaiterUnsafeOnCompletedMethod != null)
{
// var unsafeOnCompletedFunc = (object awaiter, Action continuation) => {
// ((CustomAwaiterType)awaiter).UnsafeOnCompleted(continuation);
// };
var unsafeOnCompletedParam1 = Expression.Parameter(typeof(object), "awaiter");
var unsafeOnCompletedParam2 = Expression.Parameter(typeof(Action), "continuation");
unsafeOnCompletedFunc = Expression.Lambda <Action <object, Action> >(
Expression.Call(
Expression.Convert(unsafeOnCompletedParam1, awaitableInfo.AwaiterType),
awaitableInfo.AwaiterUnsafeOnCompletedMethod,
unsafeOnCompletedParam2),
unsafeOnCompletedParam1,
unsafeOnCompletedParam2).Compile();
}
// If we need to pass the method call result through a coercer function to get an
// awaitable, then do so.
var coercedMethodCall = coercedAwaitableInfo.RequiresCoercion
? Expression.Invoke(coercedAwaitableInfo.CoercerExpression, methodCall)
: (Expression)methodCall;
// return new ObjectMethodExecutorAwaitable(
// (object)coercedMethodCall,
// getAwaiterFunc,
// isCompletedFunc,
// getResultFunc,
// onCompletedFunc,
// unsafeOnCompletedFunc);
var returnValueExpression = Expression.New(
_objectMethodExecutorAwaitableConstructor,
Expression.Convert(coercedMethodCall, typeof(object)),
Expression.Constant(getAwaiterFunc),
Expression.Constant(isCompletedFunc),
Expression.Constant(getResultFunc),
Expression.Constant(onCompletedFunc),
Expression.Constant(unsafeOnCompletedFunc, typeof(Action <object, Action>)));
var lambda = Expression.Lambda <MethodExecutorAsync>(returnValueExpression, targetParameter, parametersParameter);
return(lambda.Compile());
}