VisibilityAffectsDescendants behavior now configurable for XmlSiteMapResult

[Webmarco]

Added visibilityAffectsDescendants logic to XmlSiteMapResult (flattenhierarchy). Value for the property can be set through configuration. Html helpers are not (yet) using this property. Default behavior for XmlSiteMapResult (false) is different from the Html helpers (true), what should the default be for both?
A test still needs to be written to confirm current behavior isn't broken but the change wasn't all that complicated after all.

[NightOwl888]

@Webmarco - The rest of this looks good. You may proceed with making the changes to the HTML helpers to read this new setting at your convenience.

@maartenba - If you are following along, we are amidst a breaking change where we have to make a choice because of inconsistent behavior. We either have to break the Menu/SiteMapPath/SiteMap HTML helpers by changing the default visibilityAffectsDescendants from true to false (the way it behaved in v3) or we have to break the XmlSiteMapResult by changing the default from false to true in order to allow this value to be set globally in a consistent way.

I am more inclined to break the XmlSiteMapResult now because it would be less of an impact. However, it is also less likely to be noticed right away. In that regard, breaking the Menu/SiteMapPath/SiteMap helpers would be better so people notice and can fix it. Keep in mind, this only affects people who are using visibility providers.

For the long term (v5) I would say it is better to set this default to false. To me it makes more logical sense for a visibility provider to toggle visibility of a single node rather than the node and all its children (which is how the accessibility behaves). It gives more flexibility. Furthermore, this is how it behaved originally in v3.

But the question remains what exactly to break now to make it consistent. Thoughts?

[maartenba]

I would break the HtmlHelpers, as it will be more visible for users. Unfrtunately I guess not everyone will be precompiling views and most will only notice this at runtime... Then again, I think this is probbaly the best one to get the change noticed.

[NightOwl888]

@Webmarco

I am preparing for a minor release in a few days and would like to roll these changes in. If they are not finished, I will finish them up, but I just wanted to check with you whether you have any finished code that is not yet committed or whether you have plans to finish this up. Thanks.

[Webmarco]

I'm sorry but I haven't finished this nor do I have the time to finish this in the next 2-3 weeks. I will check after that to see if I can help with anything.

[NightOwl888]

No problem. I will merge it and finish it up.