Can't setup protected methods with nullable parameters

[RobSiklos]

It seems that it's not possible to set up a protected method if it has nullable parameters.

Example:

public abstract class MyService
{
    protected abstract void MyMethod(int? val);
}

class Program
{
    static void Main(string[] args)
    {
        var mock = new Mock<MyService>();

        mock.Protected().Setup("MyMethod", (int?)1);
    }
}

The output of running this program is an ArgumentException with the following message:

Expression of type 'System.Int32' cannot be used for parameter of type 'System.Nullable1[System.Int32]' of method 'Void MyMethod(System.Nullable1[System.Int32])'

[RobSiklos]

I took a quick peek in the code and I believe the solution can be implemented easily. The reason for the problem is that when nullable values are cast to object, it's the underlying value that gets boxed, rather than the nullable instance being referenced. So we've completely lost the fact that an arg is nullable just by looking at its type.

The solution is that in ProtectedMock.ToExpressionArg(), the call to Expression.Constant() should also specify the type (using the other overload for that method).

Here are my modified versions of ToExpressionArg() and ToExpressionArgs():

private static Expression ToExpressionArg(ParameterInfo paramInfo, object arg)
{
    var lambda = arg as LambdaExpression;
    if (lambda != null)
    {
        return lambda.Body;
    }

    var expression = arg as Expression;
    if (expression != null)
    {
        return expression;
    }

    return Expression.Constant(arg, paramInfo.ParameterType);
}

private static IEnumerable<Expression> ToExpressionArgs(MethodInfo method, object[] args)
{
    ParameterInfo[] methodParams = method.GetParameters();
    for (int i = 0; i < args.Length; i++)
    {
        yield return ToExpressionArg(methodParams[i], args[i]);
    }
}

[kzu]

Looks good!

Want to send a PR so you get credited appropriately and this fix makes it
into the next release right away?

/kzu from mobile
On Mar 7, 2014 1:42 PM, "Rob Siklos" notifications@github.com wrote:

I took a quick peek in the code and I believe the solution can be
implemented easily. The reason for the problem is that when nullable values
are cast to object, it's the underlying value that gets boxed, rather
than the nullable instance being referenced. So we've completely lost the
fact that an arg is nullable just by looking at its type.

The solution is that in ProtectedMock.ToExpressionArg(), the call to
Expression.Constant() should also specify the type (using the other
overload for that method).

Here are my modified versions of ToExpressionArg() and ToExpressionArgs():

private static Expression ToExpressionArg(ParameterInfo paramInfo, object arg){
var lambda = arg as LambdaExpression;
if (lambda != null)
{
return lambda.Body;
}

var expression = arg as Expression;
if (expression != null)
{
    return expression;
}

return Expression.Constant(arg, paramInfo.ParameterType);}

private static IEnumerable ToExpressionArgs(MethodInfo method, object[] args){
ParameterInfo[] methodParams = method.GetParameters();
for (int i = 0; i < args.Length; i++)
{
yield return ToExpressionArg(methodParams[i], args[i]);
}}

Reply to this email directly or view it on GitHubhttps://github.com//issues/92#issuecomment-37041881
.

[RobSiklos]

@kzu: Unfortunately, I don't have any git integration set up (we're a TFS-based shop) and I don't have time to get it all set up and create a PR. I don't really care about being credited, so if you or someone else would be able to integrate the change, that would be great.

Thanks!

[RobSiklos]

@kzu Ok - I finally got around to doing this :) Pull request #199.

[RobSiklos]

Pull request #200 (single commit).

[RobSiklos]

@kzu Any reason why the pull request hasn't been merged yet?

[stakx]

I guess we can close this issue, now that #200 has been merged.