Should proj-info filter out empty solution folders when loading solution filters?

[Numpsy]

This is a spin off from the comments in #241 (comment), just to keep that PR as a fix for ionide/ionide-vscode-fsharp#2107 and look at filters seperately.

Say you have a solution like this

<Solution>
  <Folder Name="/A/">
    <Project Path="A/A.fsproj" />
  </Folder>
  <Folder Name="/B/">
    <Project Path="B/B.fsproj" />
  </Folder>
</Solution>

and a solution filter like this

{
  "solution": {
    "path": "solution_test.slnx",
    "projects": [
      "B\\B.fsproj"
    ]
  }
}

If you open the filter in Visual Studio then it only displays the folder that contains a loaded project:

But if you open the filter in Ionide then it displays both of the folders:

When the solution filter is loaded by proj-info using InspectSln.tryParseSln it returns the folder that isn't in the filter as well as the one that is, though the projects within that folder have been filtered out:

So the basic question is, should proj-info be filtering the folders as well as the projects here, so FsAutoComplete/Ionide don't see them at all?

[baronfel]

I think filtering makes a ton of sense - thanks for doing the analysis and providing the examples!