Microsoft.Common.tasks cleanup

[rainersigwald]

Microsoft.Common.tasks has every built-in MSBuild task duplicated between sections, one of which is

https://github.com/microsoft/msbuild/blob/3453beee039fb6f5ccc54ac783ebeced31fec472/src/Tasks/Microsoft.Common.tasks#L9-L14

I don't think we need to have back compat with dev11 any more, and $(AssemblyVersion) should never be empty with MSBuild as built from this repo.

I'm not 100% sure of the impact of just deleting all the 4.0 references; that needs to be considered.

We cannot delete the 3.5 references like

https://github.com/microsoft/msbuild/blob/3453beee039fb6f5ccc54ac783ebeced31fec472/src/Tasks/Microsoft.Common.tasks#L39

They're needed for asset compat on old projects. But they should be conditioned out on .NET Core, which they currently are not.

[Nirmal4G]

If we make Core SDK (#1686) for the common targets, it might be safe to clean up all workarounds and back-compat till v15!

Can the following be removed too? As you said $(MSBuildAssemblyVersion) will not be empty. These code paths will never hit.

msbuild/src/Tasks/Microsoft.Common.props

Line 93 in ee1c9fd

<PropertyGroup Condition="'$(MSBuildAssemblyVersion)' == '' and ('$(VisualStudioVersion)' != '' and '$(VisualStudioVersion)' &gt;= '12.0')">

msbuild/src/Tasks/Microsoft.Common.props

Lines 107 to 112 in ee1c9fd

	<!-- If building using 4.X MSBuild, we want to act like this project is TV 4.0, so override
	the custom extensibility target locations with the hard-coded 4.0 equivalent. -->
	<PropertyGroup Condition="'$(MSBuildAssemblyVersion)' == ''">
	<CustomBeforeMicrosoftCommonProps Condition="'$(CustomBeforeMicrosoftCommonProps)'==''">$(MSBuildExtensionsPath)\v4.0\Custom.Before.$(MSBuildThisFile)</CustomBeforeMicrosoftCommonProps>
	<CustomAfterMicrosoftCommonProps Condition="'$(CustomAfterMicrosoftCommonProps)'==''">$(MSBuildExtensionsPath)\v4.0\Custom.After.$(MSBuildThisFile)</CustomAfterMicrosoftCommonProps>
	</PropertyGroup>

msbuild/src/Tasks/Microsoft.Common.props

Line 117 in ee1c9fd

<Import Project="$(MSBuildExtensionsPath)\4.0\Microsoft.Common.props" Condition="'$(MSBuildAssemblyVersion)' == '' and Exists('$(MSBuildExtensionsPath)\4.0\Microsoft.Common.props')" />

We could also remove xmlns as we already removed $(MSBuildAllProjects) (thus the min MSBuild version will be v16)!