Packaging FSharp

NuGet.exe sometimes behaves strange when packaging FSharp applications or libraries. This page describes some of the common errors and workarounds.

Parameter path cannot have zero length

When running NuGet.exe pack, the following error occurs:

Attempting to build package from 'Project.fsproj'.
The value "" of the "Project" attribute in element <Import> is invalid. Parameter "path" cannot have zero length.

This error occurs when NuGet can not find the FSharp tools path, regardless whether the tools are installed or not. A workaround is to add a <PropertyGroup> element in the .fsproj file:

<PropertyGroup>
  <VisualStudioVersion Condition=" '$(VisualStudioVersion)' == '' ">12.0</VisualStudioVersion>
</PropertyGroup>

Note this element should be added right before:

<PropertyGroup>
  <MinimumVisualStudioVersion Condition="'$(MinimumVisualStudioVersion)' == ''">11</MinimumVisualStudioVersion>
</PropertyGroup>

Using this approach, the F# project system is led to use the correct path to find all required tools.

FSharp 4.1

It may be needed to make use of the FSharp 4.1 package that is shipped on NuGet, as opposed to relying our build agents have all different flavours of FSharp compiler installed/available for the user under which our agents run.

Example error messages during NuGet pack could be:

The value "" of the "Project" attribute in element <Import> is invalid.

Check this answer on StackOverflow on how to do this.