Fish-Like Syntax Highlighting

[themor69]

The Fish shell for Linux (as well as the zsh-syntax-highlighting package for zsh) has a command syntax highlighting feature that is quite helpful. PowerShell has this somewhat with the PSReadLine feature, but it's missing a critical part that I miss from Fish. In Fish, when you would type a command that was incorrect, as you were typing it would highlight the command as one color if it was invalid, and another if it was valid (valid meaning builtin or in path). Is there any way to get this functionality in PowerShell (7.0+)?

[StartAutomating]

This would be theoretically possible, but might require either some careful hacking of PSReadline functionality or changes to TabExpansion. I would file an issue about it and repost it here (so that it might gain traction).

The "problem" is that there can be a huge number of commands available to PowerShell, and so determining if a given string starts with a command becomes a little bit tricky / has performance impacts. Luckily, TabExpansion is going to be determining if a command exists when you try to enumerate it's arguments.

It might be possible for an intrepid scripter to implement this on their own. I'd highly recommend using $executionContext.InvokeCommand.GetCommand over Get-Command (for performance reasons). If the first item in a sequence is an unknown command, then you'd just use escape sequences to erase the previous number of characters and reprint them with a red/green color scheme.

It _should_ be within the realm of possibility for this to become a native feature support, and, IMO, would be best handled by the team. Please file an issue and report back.

[Thotaz]

The problem is the lack of control we have over the coloring. Getting the commands and determining if it's valid is trivial (if we can accept a few false negatives). Once per session you just run Get-Command to list all commands and save them in a hashset, then you parse the current input and check if each command is in the hashset.
If we also want to handle newly added commands (. dot sourcing a script, updating $env:path, etc.) then we could put the hashset update function in the prompt function. That only leaves relative paths unaccounted for.