Active patterns with defined with otherwise invalid name is incorrectly re-formatted

[josh-degraw]

Issue created from fantomas-online

Code

let (|``Custom Prefix``|_|) (p: string) (s: string) =
  if s.StartsWith(p) then
    Some(s.Substring(p.Length))
  else
    None

Result

let (|Custom Prefix|_|) (p: string) (s: string) =
    if s.StartsWith(p) then
        Some(s.Substring(p.Length))
    else
        None

Problem description

Please describe here the Fantomas problem you encountered. Check out our Contribution Guidelines.

Extra information

• [x] The formatted result breaks my code.
• [x] The formatted result gives compiler warnings.
• [x] I or my company would be willing to help fix this.
• [ ] I would like a release if this problem is solved.

Options

Fantomas main branch at 1/1/1990

Default Fantomas configuration

_{Did you know that you can ignore files when formatting by using a .fantomasignore file? PS: It's unlikely that someone else will solve your specific issue, as it's something that you have a personal stake in.}

[nojaf]

You should snatch the original ident text from source code in https://github.com/fsprojects/fantomas/blob/06d86ad91974467f0e82f5f0ca7d3c58eef7e859/src/Fantomas.Core/ASTTransformer.fs#L42

using creationAide.TextFromSource fallback range.

[nojaf]

Actually, we should reuse the logic of https://github.com/fsprojects/fantomas/blob/06d86ad91974467f0e82f5f0ca7d3c58eef7e859/src/Fantomas.Core/ASTTransformer.fs#L25-L42 instead (ident.idText.Length + 4 = width) perhaps.