FAQ

Why the name "Fantomas"?

There are a few reasons to choose the name as such. First, it starts with an "F" just like many other F# projects. Second, Fantomas is my favourite character in the literature. Finally, Fantomas has the same Greek root as "phantom"; coincidentally F# ASTs and formatting rules are so mysterious to be handled correctly.

What is fantomas-tool?

That is the previous name of the dotnet tool. v4.7.9 was the last stable release under that name.
Please use fantomas instead and remove all traces of fantomas-tool in your dotnet-tools.json file.

Why exit code 99 for a failed format check?

No real reason, it was suggested by the contributor lpedrosa.
It also reminds us of a certain Jay-Z song 😉.

Can I make a style suggestion?

As mention in style guide, Fantomas adheres to Microsoft and G-Research style guidelines.
For any style related suggestion, please head over to fsharp/fslang-design.
More context.

Is it safe to use the Alpha version of Fantomas?

Preview alpha versions are generally safe to use but there is no guarantee that the style wouldn't change due to ongoing development.
You should check the changelog to see if there's any relevant change to try out in the Alpha.

Why does Fantomas format my lists strangely when I pass them as arguments?

Prior to the new indexing syntax, introduced in F# 6.0, you could write code like

Radio.Input.Props[Checked false
                  OnChange(fun _ -> settings |> updateSettings)]

without the compiler nagging you about the missing space between the callee (Props) and the argument ([Checked false ...]). See issue 2754 for another example.
Since F# 6.0, Fantomas interprets the list as an index expression and formats it accordingly.
In such a case, just add a space between the callee and the list and you should be good to go.