#2782

Gotchas: Assembly Level Attributes in F#

This is something I discovered ages ago and should have been in my original Gotchas: Common Traps for the F# n00b post. I figured out how to add assembly level attributes to one of my F# assemblies but forgot to include it in the post.

The gotcha is that because F# projects don’t include a default AssemblyInfo.fs file you’re left to figure this out for yourself. If you do the obvious thing and just add the attribute (example in lines 9-13 below) you’ll see the following error:

This attribute is not valid for use on this language element. Assembly attributes should be attached to a ‘do ()’ declaration, if necessary within an F# module.

It turns out that the module needs an empty do() statement at the end of it. So your assemblyInfo.fs file might look something like this.

   1: #light

   2:  

   3: namespace NBody.DomainModel.Integrators

   4:  

   5: open System

   6: open System.Reflection;

   7: open System.Runtime.InteropServices;

   8:  

   9: [<assembly: AssemblyTitle("NBody.DomainModel.FSharp")>]

  10: [<assembly: AssemblyDescription("F# integrators")>]

  11:  

  12: [<assembly: ComVisible(false)>]

  13: [<assembly: CLSCompliant(false)>]

  14:  

  15: do()

Note the do() at line 15. Adding this fixes the problem and the code compiles.