Monday, May 14, 2018

`dotnet build`ing Eto.Forms projects

A couple of months back, Scott Hanselman blogged about the Eto.Forms cross-platform UI toolkit for .net. I filed that away for reference, and this weekend got around to giving it a whirl.

So I took the default new F# app and made a personalized little skeleton project (standard boiler-plate for the "About..." dialog, that sort of thing), and as part of making it re-usable as such, added a trivial FAKE build script. Eto.Forms generates new-style projects, so of course that would be using the and DotNet.publish tasks...

Not so fast.

Do that and it barfs with

error : MSB4801: The task factory "CodeTaskFactory" is not supported on the .NET Core version of MSBuild.
error MSB4175: The task factory "CodeTaskFactory" could not be loaded from the assembly "C:\Program Files\dotnet\sdk\2.1.200\Microsoft.Build.Tasks.Core.dll". The task factory must return a value for the "TaskType" property.

which turns out to be a known issue (or two). Rather than sit tight and wait, I did a bit of looking around. Turns out there's a similar, closed, issue against msbuild itself, to which the resolution is to use the RoslynCodeTaskFactory as a replacement.

So, after some experimentation, here's a work-around while a fix works its way through the system; it functions by overriding the _BuildAppBundle target, so can be fitted into existing build processes without hacking any of your downloaded packages.

  1. Add the RoslynCodeTaskFactory NuGet package to each affected project (probably just the .Desktop one
  2. Get the override target file MacTemplateOverride.targets from this gist
  3. Adjust the path to your eto.platform.mac64 version (assumed 2.4.1 in default location) as needed

  4. Add <Import Project="[path to]\MacTemplateOverride.targets" /> at the end of each affected project to load the file from where you've saved it in your solution

  5. dotnet build

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