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[Charlie Poole <question238356@xxxxxxxxxxxxxxxxxxxxx>]

Question #238356 on NUnit Framework changed:
https://answers.launchpad.net/nunit-3.0/+question/238356

Charlie Poole proposed the following answer:
It looks like a good approach to me.

It looks as if you won't even be called unless the correct number of
arguments are provided, which is good. We may want to deal with default
arguments at some point in the future, but for now it's better to keep that
a separate issue.

Charlie


On Thu, Oct 31, 2013 at 11:31 AM, Danil Flores <
question238356@xxxxxxxxxxxxxxxxxxxxx> wrote:

> Question #238356 on NUnit Framework changed:
> https://answers.launchpad.net/nunit-3.0/+question/238356
>
> Danil Flores posted a new comment:
> The change itself is rather simple. There are two places in the code
> that use Convert.ChangeType(dataValue, targetMethodParameterType, ...);
> to attempt to convert convertible values into the actual type a
> parameter expects.
>
> Convert.ChangeType(...) crashes when the type is a nullable of a type,
> so basically the algorithm is as follows:
>
> 1. First check if the target type is Nullable using
> Nullable.GetUnderlyingType(targetType) which just returns null if the item
> is not nullable.
> 2. There's a section of if statements that determine if the value is
> convertible to something by comparing the parameter type to the proposed
> value type. If the item is nullable, compare to the underlying type instead.
> 3. Call Convert.ChangeType(...) on either the nullabletype if not null or
> the target type.
> 4. If the target type is nullable, create a NullableConverter for it and
> convert the value from step 3. into a nullable of it.
>
> Now I realize there's some conditional compilation symbols that I'd
> still need to add to make sure that the assembly can still be compiled
> for CLR 2.0, but here's the jist of it from
> NUnitCore\core\builders\TestCaseParameterProvider.cs in NUnit v2
>
> private static void PerformSpecialConversions(object[] arglist,
> ParameterInfo[] parameters)
> {
>     // Rest of code is omitted for brevity, this starts on line 151 in
> TestCaseParameterProvider.cs
>     Type nullableType = Nullable.GetUnderlyingType(targetType);
>     bool convert = false;
>     bool isNullable = nullableType != null;
>     Type typeToCompare = nullableType ?? targetType;
>
>     if (typeToCompare == typeof(short) || typeToCompare == typeof(byte) ||
> typeToCompare == typeof(sbyte))
>            convert = arg is int;
>     else if (typeToCompare == typeof(decimal))
>            convert = arg is double || arg is string || arg is int;
>     else if (typeToCompare == typeof(DateTime) || typeToCompare ==
> typeof(TimeSpan))
>            convert = arg is string;
>
>     if (convert)
>     {
>           arglist[i] = Convert.ChangeType(arg, nullableType ?? targetType,
> System.Globalization.CultureInfo.InvariantCulture);
>
>           if (isNullable)
>           {
>                  NullableConverter converter = new
> NullableConverter(targetType);
>                  arglist[i] = converter.ConvertFrom(arglist[i]);
>           }
>     }
> }
>
> There is a similar change to NUnitTestCaseBuilder as well to ensure that
> the types match up. Those were the only two areas that I found were
> doing the conversion, but feel free to let me know if I've missed
> something. Do you think this approach is the best way to go?
>
> (By the way, not sure how this comment thread treats whitespace, so I
> apologize if the code snippet comes out poorly formatted).
>
>
> Thanks!
> Danil M. Flores
>
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