Continuation prompt (PS2)

[JanDeDobbeleer]

I was going through the docs but couldn't immediately find if there's a prompt filter available for a continuation prompt. We recently added that functionality to oh-my-posh so I was looking at porting this to clink as well.

[chrisant996]

That's correct, Clink currently doesn't support customizing the continuation prompt, and doesn't enable any of its input line editing support in the continuation prompt.

I haven't taken any steps down that path because:

1. There isn't a reliable enough way to detect when CMD shows the continuation prompt. Currently Clink uses the combination of seeing a particular string, plus having additional lines already queued up, and then it auto-responds with pretty high confidence to a continuation prompt. But when there aren't already lines queued up, there isn't a reliable enough way detect whether it's a really continuation prompt.
2. Clink also doesn't understand how to lex and parse CMD syntax for the ( and ) grouping symbols, and doesn't understand any CMD control statements (if, for, and so on). It gets very complicated very quickly (and expensive, and likely unreliable). I don't currently plan to teach Clink about any of those. So, adding more support for fancy continuation prompt behaviors would likely set a misleading precedent.

[JanDeDobbeleer]

Thanks, just wanted to make sure I didn't miss anything obvious 🙏🏻

[chrisant996]

The question got my subconscious thinking about it:

1. I realized there's already a problem with ( echo foo ): Clink thinks ( is the command and doesn't handle argmatchers correctly.
   • Item 1 is worth addressing no matter what.
2. I realized parsing the ( and ) grouping symbols can take some shortcuts.
   • Item 2 is worth doing to solve item 1, and also to support coloring the ( and ) appropriately (instead of as commands or arguments).
3. I realized a way to trick CMD and reliably detect the continuation prompt.
   • I will likely hook up Clink's input line to work in the continuation prompt.
   • I may add a way to filter the continuation prompt, but I haven't decided yet.

[JanDeDobbeleer]

This response is so relatable 😄 I can't even count the times where I made an elaborate statement on something not being feasible only to come to a solution a day or so later. Let me know how it evolves and if I can somehow hook into it 🙏🏻

[chrisant996]

The shortcuts I hoped to take for parsing the ( and ) grouping symbols don't really work. Proper parsing looks very complicated and requires special handling (and quirks) for rem, if, for, etc.

Items 1 and 3 still look feasible.

Item 2 is more involved:

• Handling leading ( is feasible.
• Handling parsing open/close levels for parentheses is feasible.
  • But rem messes that up because it eats the whole rest of the line.
  • But rem already messes up & and | parsing.
  • A special exception can be made for rem.
• Truly accurate handling of ( and ) syntax -- and syntax errors -- is very complicated.
• I'll look for a way to apply the "80 / 20 rule". I don't think it's worth the cost of being entirely/pedantically accurate.

[chrisant996]

The following makes the continuation prompt super complicated to handle in any kind of reasonable way:

C:\somewhere> echo hello wor^
More? _

That's why I had decided not to even try to support the continuation prompt.

So, all that I'm going to do is:

• Handle the rem issue.
• Skip past leading ( when looking up an argmatcher for the command.
  • Except when the ( is part of a doskey macro name.
• Resolve doskey macros in ( macro ) when doskey.enhanced is enabled.
• Maybe: I might add coloring for ( and ), and possibly even add coloring for some syntax errors related to ( and ) usage.

No continuation prompt support.