Fixes #94 - adds support for conditional breakpoints

[rkeithhill]

This adds some unit tests for conditional breakpoints and refactors some existing unit tests I wrote to be a bit more DRY. Also, VSCode supports column breakpoints in its protocol. And PowerShell supports breakpoints on columns other than 1. So why don't I see any UI in VSCode to create a breakpoint at a specific column? Is there something we have to do to declare support for column breakpoints?

[daviwil]

This is awesome!

[daviwil]

This is great work man, I'm really excited for this feature to come online! If you're ready you can merge it.

[daviwil]

Regarding column breakpoints, I haven't seen anything in the UI for that yet. Was sort of expecting that I could put the cursor somewhere, right click and Add Breakpoint but it's not there. We might have to ask about that.

[rkeithhill]

It is weird that the protocol supports column breakpoints but the UI doesn't. Oh well. At least we will have conditional breakpoints.

BTW I ran into a "gotcha" - ScriptBlock parsing will catch a number of parse errors but it won't catch this $i == 3. It parses as an assignment with $i on the LHS and, get this, = 3 on the RHS. So yeah, in PowerShell you can actually create a command named = e.g.:

function = { Write-Warning "What do you think this is - C#?" }
$i == 1

Outputs:

WARNING: What do you think this is - C#?

This is a bummer because somebody will invariably forget to use -eq and the breakpoint won't hit. I guess I could try to handle two "special" cases e.g.LHS == RHS and LHS > RHS by inspecting the AST and generating an error message? The other combinations of !=, >=, < and <= generate parse errors. What do you think?

[daviwil]

Yeah, if there's a way to catch that and throw an error (especially suggesting the usage of -eq and -gt) then that would be ideal. This is a weird case where I'd expect the language would throw an error since it's kind of a common issue for people coming over from C#. I know I've hit it in the past...

[rkeithhill]

Ask and you shall receive:

[daviwil]

That looks great!