Does Scriban support .NET Object Indexers ?

[CADbloke]

Firstly, thanks for this awesome library. I am investigating using it in an app that will retrieve data for CAD drawings of wiring diagrams for television stations, just in case you thought you'd heard every use-case.

My question: does the .NET object property retrieval support class indexers like Thing["Index"] where Index isn't an actual property but rather the argument for an indexer lookup? For a MSFT example on indexers - https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/indexers/using-indexers#example-2

cheers

[CADbloke]

I think I can answer my own question here: "not yet" and "looks tricky". Or it does and I missed it,

Looking at https://github.com/lunet-io/scriban/blob/63ad634ffaf55cd4b8e72d1342f979520934c5be/src/Scriban/Runtime/Accessors/TypedObjectAccessor.cs at TryGetValue is only looks up fields and properties.

I found https://stackoverflow.com/questions/14462820/check-if-indexing-operator-exists/14462921#14462921 for reference on indexers and how to find it.

related: #116

I tried adding this code to TryGetValue ...

var indexer = _type.GetProperties().FirstOrDefault(p => p.GetIndexParameters().Length != 0
                                                      && !typeof(IList).IsAssignableFrom(_type));

if (indexer != null)
{
    object[] indexArgs = { member };

    try
    {
        value = indexer.GetValue(target, indexArgs);
    }
    catch (Exception )
    {
        return false;
    }
    return true;
}

return false;

but it broke .NET standard v1 & it also bypasses any filters etc. so it's not pull-request worthy.

Severity	Code	Description	Project	File	Line	Suppression State
Error	CS1061	'Type' does not contain a definition for 'GetProperties' and no accessible extension method 'GetProperties' accepting a first argument of type 'Type' could be found (are you missing a using directive or an assembly reference?)	Scriban(netstandard1.1), Scriban(netstandard1.3)	D:\CodezOnD\Github\scriban\src\Scriban\Runtime\Accessors\TypedObjectAccessor.cs	63	Active

I added this test to https://github.com/lunet-io/scriban/blob/548998cbebb27534dcd36526ab0f2535ea81c237/src/Scriban.Tests/TestRuntime.cs (at line 730)

[Test]
        public void TestIndexerOnNETwithIndex()
        {
            var myobject = new MyObjectHasIndexer() { FieldA = "yo"};
            var result   = Template.Parse("{{obj['xxx']}}").Render(new ScriptObject() {{"obj", myobject}});
            Assert.AreEqual("found", result);
        }

        private class MyObjectHasIndexer : MyStaticObject
        {
            public string FieldA;

            public string FieldB;

            public string PropertyA { get; set; }

            public string PropertyB { get; set; }

            public string this[string key]
            {
                get
                {
                    if (key == "xxx")
                        return "found";

                    return null;
                }
                set{}
            }
        }

and it passed in .NET 3.5. but everything else seems broken. Oops

Your thoughts?

[xoofx]

The commit 14b0b17 should fix this issue. it will be part of the next release

[CADbloke]

Thank you!

Sorry about my delay in responding. This is much appreciated. I will put together some tests of the way I plan to implement it and let you know how I go. It will probably me a couple of months before I have my shit together but this definitely opens up a lot of possibilities.

Thanks again
Ewen