<Import> is emitted after <Choose>

Description

Current versions of Paket emit the <Choose> and <Import Project=...> tags in the incorrect order. It should first emit the <Import> tag, but it first emits the <Choose> tag. This results in problems when using the Roslyn compiler, because the following packages require the proper order of these tags:

• Microsoft.Net.Compilers
• Microsoft.CodeDom.Providers.DotNetCompilerPlatform

Repro steps

1. Add the Microsoft.Net.Compilers and Microsoft.CodeDom.Providers.DotNetCompilerPlatform to the project.
2. Run paket update.
3. Recompile the project.

This will show the following error:

C:\Program Files (x86)\MSBuild\14.0\bin\Microsoft.CSharp.Core.targets(76,11): error MSB4064: The "ChecksumAlgorithm" parameter is not supported by the "Csc" task. Verify the parameter exists on the task, and it is a settable public instance property.
C:\Program Files (x86)\MSBuild\14.0\bin\Microsoft.CSharp.Core.targets(67,5): error MSB4063: The "Csc" task could not be initialized with its input parameters. 

To fix this problem, the .csproj file has to be changed manually. This is the file that is generated by Paket:

  <Choose>
    <When Condition="$(TargetFrameworkIdentifier) == '.NETFramework' And ($(TargetFrameworkVersion) == 'v4.5.2' Or $(TargetFrameworkVersion) == 'v4.5.3' Or $(TargetFrameworkVersion) == 'v4.6' Or $(TargetFrameworkVersion) == 'v4.6.1' Or $(TargetFrameworkVersion) == 'v4.6.2' Or $(TargetFrameworkVersion) == 'v4.6.3')">
      <PropertyGroup>
        <__paket__Microsoft_Net_Compilers_props>Microsoft.Net.Compilers</__paket__Microsoft_Net_Compilers_props>
      </PropertyGroup>
    </When>
  </Choose>
  <Import Project="..\packages\Microsoft.Net.Compilers\build\$(__paket__Microsoft_Net_Compilers_props).props" Condition="Exists('..\packages\Microsoft.Net.Compilers\build\$(__paket__Microsoft_Net_Compilers_props).props')" Label="Paket" />
  <Choose>
    <When Condition="$(TargetFrameworkIdentifier) == '.NETFramework' And ($(TargetFrameworkVersion) == 'v4.5.2' Or $(TargetFrameworkVersion) == 'v4.5.3' Or $(TargetFrameworkVersion) == 'v4.6' Or $(TargetFrameworkVersion) == 'v4.6.1' Or $(TargetFrameworkVersion) == 'v4.6.2' Or $(TargetFrameworkVersion) == 'v4.6.3')">
      <PropertyGroup>
        <__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props>Microsoft.CodeDom.Providers.DotNetCompilerPlatform</__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props>
      </PropertyGroup>
    </When>
  </Choose>
  <Import Project="..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform\build\$(__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props).props" Condition="Exists('..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform\build\$(__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props).props')" Label="Paket" />
  <Import Project="$(VSToolsPath)\WebApplications\Microsoft.WebApplication.targets" Condition="'$(VSToolsPath)' != ''" />
  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets" Condition="false" />

It should be changed to:

  <Import Project="..\packages\Microsoft.Net.Compilers\build\$(__paket__Microsoft_Net_Compilers_props).props" Condition="Exists('..\packages\Microsoft.Net.Compilers\build\$(__paket__Microsoft_Net_Compilers_props).props')" Label="Paket" />
  <Choose>
    <When Condition="$(TargetFrameworkIdentifier) == '.NETFramework' And ($(TargetFrameworkVersion) == 'v4.5.2' Or $(TargetFrameworkVersion) == 'v4.5.3' Or $(TargetFrameworkVersion) == 'v4.6' Or $(TargetFrameworkVersion) == 'v4.6.1' Or $(TargetFrameworkVersion) == 'v4.6.2' Or $(TargetFrameworkVersion) == 'v4.6.3')">
      <PropertyGroup>
        <__paket__Microsoft_Net_Compilers_props>Microsoft.Net.Compilers</__paket__Microsoft_Net_Compilers_props>
      </PropertyGroup>
    </When>
  </Choose>
  <Import Project="..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform\build\$(__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props).props" Condition="Exists('..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform\build\$(__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props).props')" Label="Paket" />
  <Import Project="$(VSToolsPath)\WebApplications\Microsoft.WebApplication.targets" Condition="'$(VSToolsPath)' != ''" />
  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets" Condition="false" />
  <Choose>
    <When Condition="$(TargetFrameworkIdentifier) == '.NETFramework' And ($(TargetFrameworkVersion) == 'v4.5.2' Or $(TargetFrameworkVersion) == 'v4.5.3' Or $(TargetFrameworkVersion) == 'v4.6' Or $(TargetFrameworkVersion) == 'v4.6.1' Or $(TargetFrameworkVersion) == 'v4.6.2' Or $(TargetFrameworkVersion) == 'v4.6.3')">
      <PropertyGroup>
        <__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props>Microsoft.CodeDom.Providers.DotNetCompilerPlatform</__paket__Microsoft_CodeDom_Providers_DotNetCompilerPlatform_props>
      </PropertyGroup>
    </When>
  </Choose>

As you can see, the order of the <Import> and <Choose> tags has been changed. This will allow the project to be compiled again.

Expected behavior

<Choose> tags should be emitted after the <Import> tags of the package.

Actual behavior

<Choose> tags should is emitted before the <Import> tags of the package.

Known workarounds

The only workaround is to patch the .csproj by hand.

Related information

This issue exists for a few weeks now. It’s still in 3.16.2.

[isaacabraham]

Hmmm. I’ve just run into the same problem now though - clean ASP .NET project, convert-from-nuget.

[enricosada]

Closing