fix prefix dupplication error

[whistyun]

If there are some namespaces of the same acronym, XamlServices.Save cause XmlException with the message "'xmlns:p' is a duplicate attribute name".

Demonstration code

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            var list = new List<object>();
            list.Add(new Charlie());
            list.Add(new Carol()); // if this line comment out, no error occured

            var txt = Portable.Xaml.XamlServices.Save(list);
            Console.WriteLine(txt);
        }
    }
}

namespace Alpha.Bravo
{
    public class Charlie
    {
        public Chocolate FavoriteFood { set; get; } = new Chocolate();
    }
}

namespace Alice.Bob
{
    public class Carol
    {
        public Chocolate FavoriteFood { set; get; } = new Chocolate();
    }
}

namespace Apple.Banana
{
    public class Chocolate
    {
    }
}

This pull request avoids the above problem by adding an ordinal number at the end

[whistyun]

I think this build failure is bacause of it.
Should I modify yml file for workaround?

[cwensley]

Thanks for submitting the PR! This is great.

There's a few things.. would you be able to write it without having a capturing lambda or enumerable (foreach)? Also, a test would be great to have to ensure this doesn't break in the future.

[cwensley]

.. as for the build error, yes if you know what is needed to be done to fix It please update. I'll probably update this to use .NET 5 soon anyway.

[whistyun]

would you be able to write it without having a capturing lambda or enumerable (foreach)?

I can't come up with a way to write without 'Any' method nor enumerable.
I'm going to avoid call 'Any' in while loop. However don't you mean it?

public string AddNamespace (string ns)
{
	var l = Namespaces;
	string prefix, s;

	...

	else
	{
		s = sctx.GetPreferredPrefix(ns);
		if (!l.Any(i => i.Prefix == s))
			prefix = s;
		else 
		{
			int getSuffix(string p)
				=> !p.StartsWith("p") ? 0 :
				   int.TryParse(p.Substring(1), out var i) ? i :
				   1;

			var idx = l.Max(i => getSuffix(i.Prefix)) + 1;
			prefix = s + idx;
		}
	}

	...
}

[cwensley]

How about creating a function:

		bool AnyHavePrefix(List<NamespaceDeclaration> namespaces, string prefix)
		{
			for (int i = 0; i < namespaces.Count; i++)
			{
				var ns = namespaces[i];
				if (ns.Prefix == prefix)
					return true;
			}
			return false;
		}

After looking into that method, I realize there's another use of an Any() with capturing lambda in that method too... There's no reason we couldn't make it more optimized while we notice it, I hope you don't mind.

Also, just a quick question.. why do you start at 2? Does System.Xaml behave this way?

[whistyun]

When I checked System.Xaml, it started from 1.
I will match it with System.Xaml.

By the way, System.Xaml uses the acronyms, not the ‘p’ (for example, the demo code uses ‘ab’, ‘ab1’, ‘ab2’).

If possible, if GetPreferredPrefix returns 'p', I will use the acronyms instead.
If we can get the acronyms, I will use the acronyms and when prefix duplication is occurred, add suffix to the acronyms. If we can't get the acronym, use GetPreferredPrefix as an alternative.

[whistyun]

@cwensley
I fixed to start from 1. and If a acronyms is gotten, it 's used.
I Also added some test cases.

Additionary, I added workaround build.yml to avoid build failure.