Provide symbol outline for psd1 files

[kapilmb]

This update will show the list of keys present in a psd1 file when a user invokes Go to Symbols in File... (Ctrl+Shift+O) on an psd1 file.

[daviwil]

Slight typo, FindHashtabeSymbolsVisitor

[kapilmb]

@daviwil rebased on develop, fixed the typo and updated inline docs.

[daviwil]

This is pretty awesome! Really handy to jump down to a specific field in the file, even in nested structures. It'd be really nice if we could also jump to commented-out fields too but based on some brief research there seems to be no Ast class or visitor for comment lines. Any thoughts on how we might be able to do that?

[daviwil]

Hmmm, we might be able to use the list of tokens returned by the parser to find them. There's a TokenKind.Comment here: https://msdn.microsoft.com/en-us/library/system.management.automation.language.tokenkind%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396

[rkeithhill]

there seems to be no Ast class or visitor for comment lines

I've asked Jason about this. This is one area where I wish PowerShell were more like Roslyn which retains all source code trivia (like whitespace between tokens and comments).

[daviwil]

I've considered creating a higher-level abstraction that can (literally) fill in the gaps of the Ast for things like that. I think we're going to need it for making code formatting rules in PSScriptAnalyzer.

[kapilmb]

I think we can tackle some basic scenarios without needing any help from Asts. For example,

@{
  ModuleVersion = 0.1
  Author = "XYZ"
 # RootModule = ".\test.psm1"
 # FunctionsToExport = @('get-foo')
}

Here, we just extract out the commented fields with some regular expression help.

[daviwil]

@kapilmb I think this PR is done, right? Can I merge it?

[kapilmb]

Yes, this done.

[daviwil]

Cool! Merging it.