Add worker extension validation to CI (#2764)

Directory.Build.props

@@ -11,4 +11,8 @@
     <TargetsRoot>$(EngRoot)build/</TargetsRoot>
   </PropertyGroup>
 
+  <PropertyGroup Condition="'$(TF_BUILD)' == 'true'">
+    <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
+  </PropertyGroup>
+
 </Project>

eng/build/WorkerExtensions.targets

@@ -1,4 +1,9 @@
 <Project>
+    <PropertyGroup>
+        <_ExtensionProjectTemplate>$(MSBuildThisFileDirectory)/extensionValidationProjectTemplate.txt</_ExtensionProjectTemplate>
+        <_ExtensionValidationLocation>$(IntermediateOutputPath)ExtensionValidation/</_ExtensionValidationLocation>
+    </PropertyGroup>
+
     <Target Name="AddWebJobsExtensionInformation" BeforeTargets="GetAssemblyAttributes" Condition="'@(WebJobsExtension)' != ''">
         <ItemGroup>
             <_ExtensionInformationAttribute Include="@(WebJobsExtension->'Microsoft.Azure.Functions.Worker.Extensions.Abstractions.ExtensionInformationAttribute')">
@@ -8,4 +13,18 @@
             <AssemblyAttribute Include="@(_ExtensionInformationAttribute)" RemoveMetadata="Version" />
         </ItemGroup>
     </Target>
+
+    <Target Name="GenerateExtensionProject" AfterTargets="Compile" Condition="'@(WebJobsExtension)' != '' and '$(ContinuousIntegrationBuild)' == 'true'">
+        <MakeDir Directories="$(_ExtensionValidationLocation)" />
+        <WriteLinesToFile
+            File="$(_ExtensionValidationLocation)ExtensionValidation.csproj"
+            Lines="$([System.IO.File]::ReadAllText($(_ExtensionProjectTemplate))
+                .Replace('$PackageName$', '%(WebJobsExtension.Identity)')
+                .Replace('$PackageVersion$', '%(WebJobsExtension.Version)'))"
+            Overwrite="true" />
+    </Target>
+
+    <Target Name="RestoreGeneratedExtensionProject" AfterTargets="GenerateExtensionProject" Condition="'@(WebJobsExtension)' != '' and '$(ContinuousIntegrationBuild)' == 'true'">
+        <MSBuild Projects="$(_ExtensionValidationLocation)ExtensionValidation.csproj" Targets="Restore" />
+    </Target>
 </Project>

eng/build/extensionValidationProjectTemplate.txt

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <TargetFramework>net8.0</TargetFramework>
+        <OutputType>Library</OutputType>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="$PackageName$" Version="$PackageVersion$" />
+    </ItemGroup>
+</Project>