Named string argument to type provider requires a space prior to '@', which Fantomas removes

[reinux]

Issue created from fantomas-online

Code

type Graphml = XmlProvider<Schema= @"http://graphml.graphdrawing.org/xmlns/1.0/graphml-structure.xsd">

Error

Fantomas was able to format the code but the result appears to be invalid F# code.
Please open an issue.

Formatted result:

type Graphml = XmlProvider<Schema=@"http://graphml.graphdrawing.org/xmlns/1.0/graphml-structure.xsd">

Problem description

F# requires the '@' to have a space before it in type provider arguments. This makes sense, as <@ is used for code quotations.

Weirdly, the compiler also requires a space even if the preceding token isn't a '<', e.g. if it's a = or a ,.

I think Fantomas is behaving correctly, but unless the fsc parser can be fixed by 5.0's release, it may be preferable to work around it.

If you agree that this should be addressed by Fantomas, I'd like to try tackling this bug (along with the other disappearing comments one), but I don't know if I'll have time to study Fantomas' workings for at least a couple more weeks :(

I've submitted an issue on dotnet/fsharp as well.

Extra information

• The formatted result breaks by code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas Master at 10/26/2020 19:07:04 - be9212d

Default Fantomas configuration

[nojaf]

I think we can extract firstItemHasAtSignBeforeString and re-use it to solve this issue.