The Cake GetVersion - Duplicate 'AssemblyInformationalVersion' attribute

For some reason, there is an error during cakebuild.net task execution.

The root cause of error is UpdateAssemblyInfo = true property. It's look like attribute duplication happens.

But it's not obvious why it happens for me. Could you pls, reveal such kind of behavior

Prerequisites:

Net 4.7.2
Not AssemblyInformationalVersion attribute in .csproj

Not AssemblyInformationalVersion attribute in Properties\AssemblyInfo

var gitVersion = GitVersion(new GitVersionSettings
             {
                 OutputType = GitVersionOutput.Json,
                 NoFetch = false,
                 UpdateAssemblyInfo = true
             });

Error:

Properties\AssemblyInfo.cs(41,12): error CS0579: Duplicate 'AssemblyInformationalVersion' attribute

Solution

For SDK style projects AssemblyInfo will always be generated (unless <GenerateAssemblyInfo>false</GenerateAssemblyInfo> is set). The generated AssemblyInfo will contain some version information, regardless whether you set <AssemblyInformationalVersion> explicitly, or not.

So: Setting UpdateAssemblyInfo=true in GitVersion creates an AssemblyInfo, and your csproj also creates one. Hence, the error.

What you can do: Get the version and set build properties accordingly, so the generated AssemblyInfo contains the information you want it to.

Task("Build")
.Does(() => {
   // get version
   var gitVersion = GitVersion();
   var version = gitVersion.SemVer; // or something other...
   Information($"Building version: {version}");

   // add version to settings
   var settings = new DotNetBuildSettings();
   settings.MSBuildSettings = new DotNetCoreMSBuildSettings();
   settings.MSBuildSettings.Properties.Add("AssemblyVersion", new[] { version });
   settings.MSBuildSettings.Properties.Add("AssemblyFileVersion", new[] { version });
   settings.MSBuildSettings.Properties.Add("AssemblyInformationalVersion", new [] { version });
   settings.MSBuildSettings.Properties.Add("Version", new [] { version });

   // build
   DotNetBuild("./console/console.csproj", settings);
});