Unusual characters in Ionide tooltip

[Darkle]

Describe the bug

Unusual characters are appearing in the vscode tooltips when using Ionide.

Steps to reproduce

1. Type something like asd in your code
2. Hover over it
3. You should see odd characters in the tooltip

Screenshots

• 
• Discord user Christian's screenshot:

Machine info

• OS: debian linux bullseye
• .NET SDK version: 7.0.401
• Ionide version: v7.12.4
• vscode 1.82.2

Additional context

https://discord.com/channels/196693847965696000/524660202864377896/1157997202128519188

[Martin521]

I would consider this a compiler bug. Some new error message are "semi-formatted" (including newlines). I don't think they should be.

[Darkle]

Some additional context; it doesn't seem to happen in .fsx files: https://discord.com/channels/196693847965696000/524660202864377896/1229726085546119200

[MrLuje]

The character is a UnicodeCategory.ParagraphSeparator so I guess, it is a preformatted diagnostic as stated by @Martin521
On fs files it is a ParagraphSeparator but a regular \n on fsi files.

From what I see, it's directly coming from "F# Compiler" diagnostics
https://github.com/ionide/FsAutoComplete/blob/bc827fb748e9b38615dda6f51732072e56bfdb1f/src/FsAutoComplete/LspServers/AdaptiveServerState.fs#L485-L488

A few questions :

• can we reformat the message with linebreaks in FSAC https://github.com/ionide/FsAutoComplete/blob/main/src/FsAutoComplete/LspHelpers.fs#L101-L116 ?
• if yes, should it impact all IDE relying on FSAC ? (ex: does ionide-vim handle ParagraphSeparator properly or is also impacted by this issue ?)
• or should it be fixed directly in compiler ?

[baronfel]

Good investigation @MrLuje! I think we can approach this in a few places:

• Do the newline replacement on the message in FSAC
• Raise an issue/discussion on dotnet/fsharp for clarification about the intent here
• Longer term, this particular event could be moved to the new infrastructure that @nojaf and others have created where the diagnostic can contain data that would provide the suggestions directly instead of us having to format the new lines.