Allow sharing version computation with a user-owned project

Quickbuild requires that every P2P be to a git-controlled project. This makes it incompatible with NB.GV's running the MSBuild task to one of its own .targets files. To workaround this, a quickbuild user will have to define their own project that does nothing but compute the version using NB.GV, and then set `NBGV_CachingProjectReference` to the full path to this custom project. Note that no actual *caching* occurs at this stage when under quickbuild because quickbuild uses a new top-level msbuild call for every project. We'll need to combine this with caching version info to a file on disk for this to be a perf improvement in quickbuild.
dotnet · Oct 9, 2021 · f0e05d1 · f0e05d1
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diff --git a/doc/quickbuild.md b/doc/quickbuild.md
@@ -0,0 +1,55 @@
+# Microsoft's (internal) quickbuild
+
+Nerdbank.GitVersioning supports the Microsoft-internal quickbuild/cloudbuild tool.
+
+It works out of the box, but each project will recompute the version, which may accumulate to a significant increase in overall build time.
+
+🚧 A future version of Nerdbank.GitVersioning will cache version information as a file so that the following instructions will be effective. 🚧
+
+To calculate the version just once for an entire build, a few manual steps are required.
+
+1. Create this project in your repo. The suggested location is `VersionGeneration/VersionGeneration.msbuildproj`.
+
+    ```xml
+    <Project Sdk="Microsoft.Build.NoTargets">
+      <PropertyGroup>
+        <TargetFramework>net5.0</TargetFramework>
+        <IsPackable>false</IsPackable>
+        <SkipCopyBuildProduct>true</SkipCopyBuildProduct>
+        <NBGV_CacheMode>VersionGenerationTarget</NBGV_CacheMode>
+      </PropertyGroup>
+    </Project>
+    ```
+
+    The `TargetFramework` property value is not important as no assemblies are built by this project,
+    but a value is nonetheless required for NuGet to be willing to consume the Nerdbank.GitVersioning package reference
+    (which is referenced in Directory.Build.props as described later).
+
+1. Add the SDK version to your repo-root level `global.json` file, if it is not already present.
+    The [latest available version from nuget.org](https://www.nuget.org/packages/microsoft.build.notargets) is recommended.
+
+    ```json
+    {
+      "msbuild-sdks": {
+        "Microsoft.Build.NoTargets": "3.1.0"
+      }
+    }
+    ```
+
+1. Modify your repo-root level `Directory.Build.props` file to contain these elements:
+
+    ```xml
+    <PropertyGroup>
+      <!-- This entire repo has just one version.json file, so compute the version   once and share with all projects in a large build. -->
+      <GitVersionBaseDirectory>$(MSBuildThisFileDirectory)</GitVersionBaseDirectory>
+    </PropertyGroup>
+
+    <PropertyGroup Condition=" '$(QBuild)' == '1' ">
+      <NBGV_CacheMode>MSBuildTargetCaching</NBGV_CacheMode>
+      <NBGV_CachingProjectReference>$(MSBuildThisFileDirectory)VersionGeneration\VersionGeneration.msbuildproj</NBGV_CachingProjectReference>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <PackageReference Include="Nerdbank.GitVersioning" Version="3.5.*" PrivateAssets="all" />
+    </ItemGroup>
+    ```
diff --git a/src/NerdBank.GitVersioning.Tests/NerdBank.GitVersioning.Tests.csproj b/src/NerdBank.GitVersioning.Tests/NerdBank.GitVersioning.Tests.csproj
@@ -12,7 +12,7 @@
     <Compile Include="..\Shared\**\*.cs" LinkBase="Shared" />
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="..\Nerdbank.GitVersioning.Tasks\build\*.targets;..\Nerdbank.GitVersioning.Tasks\build\*.props">
+    <EmbeddedResource Include="..\Nerdbank.GitVersioning.Tasks\build\*.targets;..\Nerdbank.GitVersioning.Tasks\build\*.props;..\Nerdbank.GitVersioning.Tasks\build\*.proj">
       <Visible>false</Visible>
       <Link>Targets\%(FileName)%(Extension)</Link>
     </EmbeddedResource>

diff --git a/src/Nerdbank.GitVersioning.Tasks/Nerdbank.GitVersioning.nuspec b/src/Nerdbank.GitVersioning.Tasks/Nerdbank.GitVersioning.nuspec
@@ -52,9 +52,9 @@ IMPORTANT: The 3.x release may produce a different version height than prior maj
     <file src="build\MSBuildTargetCaching.targets" target="build\MSBuildTargetCaching.targets" />
     <file src="build\Nerdbank.GitVersioning.Common.targets" target="build\Nerdbank.GitVersioning.Common.targets" />
     <file src="build\Nerdbank.GitVersioning.Inner.targets" target="build\Nerdbank.GitVersioning.Inner.targets" />
-    <file src="build\Nerdbank.GitVersioning.Inner.Empty.targets" target="build\Nerdbank.GitVersioning.Inner.Empty.targets" />
     <file src="build\Nerdbank.GitVersioning.props" target="build\Nerdbank.GitVersioning$LKGSuffix$.props" />
     <file src="build\Nerdbank.GitVersioning.targets" target="build\Nerdbank.GitVersioning$LKGSuffix$.targets" />
+    <file src="build\PrivateP2PCaching.proj" target="build\PrivateP2PCaching.proj" />
     <file src="buildCrossTargeting\Nerdbank.GitVersioning.targets" target="buildCrossTargeting\Nerdbank.GitVersioning$LKGSuffix$.targets" />
     <file src="readme.txt" target="readme.txt" />
   </files>

diff --git a/src/Nerdbank.GitVersioning.Tasks/build/MSBuildTargetCaching.targets b/src/Nerdbank.GitVersioning.Tasks/build/MSBuildTargetCaching.targets
@@ -6,22 +6,30 @@
     <NBGV_InnerGlobalProperties Condition=" '$(ProjectPathRelativeToGitRepoRoot)' != '' ">$(NBGV_InnerGlobalProperties)ProjectPathRelativeToGitRepoRoot=$(ProjectPathRelativeToGitRepoRoot);</NBGV_InnerGlobalProperties>
     <NBGV_InnerGlobalProperties Condition=" '$(GitVersionBaseDirectory)' != '' ">$(NBGV_InnerGlobalProperties)GitVersionBaseDirectory=$(GitVersionBaseDirectory);</NBGV_InnerGlobalProperties>
     <NBGV_InnerGlobalProperties Condition=" '$(OverrideBuildNumberOffset)' != '' ">$(NBGV_InnerGlobalProperties)OverrideBuildNumberOffset=$(OverrideBuildNumberOffset);</NBGV_InnerGlobalProperties>
-    <NBGV_InnerGlobalProperties Condition=" '$(NBGV_CacheMode)' != '' ">$(NBGV_InnerGlobalProperties)NBGV_CacheMode=$(NBGV_CacheMode);</NBGV_InnerGlobalProperties>
   </PropertyGroup>
 
   <!-- Compile a list of global properties that may vary when a project builds but that would never influence the result of the GetBuildVersion task. -->
   <ItemGroup>
     <NBGV_GlobalPropertiesToRemove Include="TargetFramework" />
     <NBGV_GlobalPropertiesToRemove Include="RuntimeIdentifier" />
-    <NBGV_GlobalPropertiesToRemove Include="Configuration" />
-    <NBGV_GlobalPropertiesToRemove Include="Platform" />
 
     <_BuildMetadataSnapped Include="@(BuildMetadata)" />
   </ItemGroup>
 
+  <!-- We generally prefer to clear config|platform properties because they do not impact the version.
+       But quickbuild doesn't like a p2p that removes these, so set them to defensible constant values in that situation. -->
+  <PropertyGroup Condition=" '$(QBuild)' == '1' ">
+    <NBGV_InnerGlobalProperties>$(NBGV_InnerGlobalProperties)Configuration=Release;</NBGV_InnerGlobalProperties>
+    <NBGV_InnerGlobalProperties>$(NBGV_InnerGlobalProperties)Platform=AnyCPU;</NBGV_InnerGlobalProperties>
+  </PropertyGroup>
+  <ItemGroup Condition=" '$(QBuild)' != '1' ">
+    <NBGV_GlobalPropertiesToRemove Include="Configuration" />
+    <NBGV_GlobalPropertiesToRemove Include="Platform" />
+  </ItemGroup>
+
   <ItemGroup>
     <!-- Declare a P2P so that "msbuild -graph -isolate" doesn't complain when we use the MSBuild task to invoke our inner shared project. -->
-    <ProjectReference Include="$(MSBuildThisFileDirectory)Nerdbank.GitVersioning.Inner.targets">
+    <ProjectReference Include="$(NBGV_CachingProjectReference)">
       <Targets>GetBuildVersion_Properties;GetBuildVersion_CloudBuildVersionVars</Targets>
       <Properties>$(NBGV_InnerGlobalProperties)BuildMetadata=@(BuildMetadata, ',');</Properties>
       <GlobalPropertiesToRemove>@(NBGV_GlobalPropertiesToRemove)</GlobalPropertiesToRemove>
@@ -32,6 +40,7 @@
       <SkipGetTargetFrameworkProperties>true</SkipGetTargetFrameworkProperties>
       <Visible>false</Visible>
       <NBGV_InnerProject>true</NBGV_InnerProject>
+      <PrivateAssets>all</PrivateAssets>
     </ProjectReference>
   </ItemGroup>
 

diff --git a/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.Inner.targets b/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.Inner.targets
@@ -43,6 +43,4 @@
     <Message Importance="low" Text="NuGetPackageVersion: $(NuGetPackageVersion)" />
   </Target>
 
-  <Import Project="Nerdbank.GitVersioning.Inner.Empty.targets" Condition=" '$(NBGV_CacheMode)' == 'MSBuildTargetCaching' " />
-
 </Project>
diff --git a/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.props b/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.props
@@ -11,5 +11,10 @@
     -->
     <NBGV_CacheMode Condition=" '$(NBGV_CacheMode)' == '' and '$(QBuild)' == '1' ">None</NBGV_CacheMode>
     <NBGV_CacheMode Condition=" '$(NBGV_CacheMode)' == '' ">MSBuildTargetCaching</NBGV_CacheMode>
+
+    <!-- This property may be overridden in environments where all P2P references must be a project actually defined within the git repo directory.
+         Learn more at :/doc/quickbuild.md.
+         -->
+    <NBGV_CachingProjectReference Condition=" '$(NBGV_CachingProjectReference)' == '' ">$(MSBuildThisFileDirectory)PrivateP2PCaching.proj</NBGV_CachingProjectReference>
   </PropertyGroup>
 </Project>
diff --git a/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.targets b/src/Nerdbank.GitVersioning.Tasks/build/Nerdbank.GitVersioning.targets
@@ -38,6 +38,7 @@
       <!-- $(TargetExt) isn't set at evaluation time for us when built in wpftmp.csproj with manual imports -->
       <!-- Suppress assembly version info generation if not obviously compiling an assembly. -->
       <GenerateAssemblyVersionInfo Condition=" '$(GenerateAssemblyVersionInfo)' == '' and '$(TargetExt)' != '.dll' and '$(TargetExt)' != '.exe' ">false</GenerateAssemblyVersionInfo>
+      <GenerateAssemblyVersionInfo Condition=" '$(GenerateAssemblyVersionInfo)' == '' and '$(NBGV_CacheMode)' == 'VersionGenerationTarget' ">false</GenerateAssemblyVersionInfo>
 
       <!-- Workaround the property stomping that msbuild does (see https://github.com/microsoft/msbuild/pull/4922) with manual imports. -->
       <PrepareForBuildDependsOn>

diff --git a/...erdbank.GitVersioning.Inner.Empty.targets → ...ioning.Tasks/build/PrivateP2PCaching.proj b/...erdbank.GitVersioning.Inner.Empty.targets → ...ioning.Tasks/build/PrivateP2PCaching.proj
@@ -1,4 +1,7 @@
-<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+
+  <Import Project="Nerdbank.GitVersioning.Inner.targets" />
 
   <!-- These targets are called by MSBuild static graph because we declare a ProjectReference item to this file. -->
   <Target Name="GetTargetFrameworks" />