private Type GetDeclaredReturnType(ControllerActionDescriptor action)
{
var declaredReturnType = action.MethodInfo.ReturnType;
if (declaredReturnType == typeof(void) ||
declaredReturnType == typeof(Task) ||
declaredReturnType == typeof(ValueTask))
{
return(typeof(void));
}
// Unwrap the type if it's a Task<T>. The Task (non-generic) case was already handled.
var unwrappedType = declaredReturnType;
if (declaredReturnType.IsGenericType &&
(declaredReturnType.GetGenericTypeDefinition() == typeof(Task <>) || declaredReturnType.GetGenericTypeDefinition() == typeof(ValueTask <>)))
{
unwrappedType = declaredReturnType.GetGenericArguments()[0];
}
// If the method is declared to return IActionResult or a derived class, that information
// isn't valuable to the formatter.
if (typeof(IActionResult).IsAssignableFrom(unwrappedType))
{
return(null);
}
// If we get here, the type should be a user-defined data type or an envelope type
// like ActionResult<T>. The mapper service will unwrap envelopes.
unwrappedType = _mapper.GetResultDataType(unwrappedType);
return(unwrappedType);
}