[Feature request] Set custom fantomas path on Fantomas.Client

[ratsclub]

I propose we add a way to provide a custom path for fantomas on Fantomas.Client.

As explained on Ionide's discussion, we can't currently have an option to set a custom path for fantomas on VSCode.

Pros and Cons

Pros

The advantages of making this adjustment to Fantomas are ...

• Allows the user to freely set where fantomas is located while using VSCode
• Nix maintainers can package ionide with fantomas bundled by default (rust-analyzer is an example)

The disadvantages of making this adjustment to Fantomas are ...

• More code complexity

Affidavit (please submit!)

Please tick this by placing a cross in the box:

• I have read the Contribution Guidelines.
• I have searched both open and closed suggestions on this site and believe this is not a duplicate

Please tick all that apply:

• This is not a breaking change to Fantomas
• I or my company would be willing to help implement and/or test this
• This suggestion is part of the Microsoft style guide (please add a link to section if so)
• This suggestion is part of the G-Research style guide (please add a link to section if so)

[nojaf]

Is it possible to use a version of fantomas specified on the path with your nix thing?

See

fantomas/src/Fantomas.Client/FantomasToolLocator.fs

Lines 126 to 148 in 09635e5

	// Find an executable fantomas file on the PATH
	let private fantomasVersionOnPath () : (FantomasExecutableFile * FantomasVersion) option =
	let fantomasExecutableOnPathOpt =
	match Option.ofObj (Environment.GetEnvironmentVariable("PATH")) with
	| Some s -> s.Split([| if isWindows then ';' else ':' |], StringSplitOptions.RemoveEmptyEntries)
	| None -> Array.empty
	|> Seq.choose (fun folder ->
	if isWindows then
	let fantomasExe = Path.Combine(folder, "fantomas.exe")
	let fantomasToolExe = Path.Combine(folder, "fantomas-tool.exe")
	if File.Exists fantomasExe then Some fantomasExe
	elif File.Exists fantomasToolExe then Some fantomasToolExe
	else None
	else
	let fantomas = Path.Combine(folder, "fantomas")
	let fantomasTool = Path.Combine(folder, "fantomas-tool")
	if File.Exists fantomas then Some fantomas
	elif File.Exists fantomasTool then Some fantomasTool
	else None)
	|> Seq.tryHead

[nojaf]

Maybe having #3104 would resolve your problem as well.