SDK does not correctly resolve RazorExtension when multiple instances of RazorConfiguration are present

Fixes #2721

Author: pranavkm

src/Microsoft.NET.Sdk.Razor/build/netstandard2.0/Sdk.Razor.CurrentVersion.targets

@@ -276,10 +276,10 @@ Copyright (c) .NET Foundation. All rights reserved.
  Condition="'$(RazorDefaultConfiguration)'!=''">
 
  <ItemGroup>
- <ResolvedRazorConfiguration Include="@(RazorConfiguration)" Condition="'%(RazorConfiguration.Identity)'=='$(RazorDefaultConfiguration)'" />
+ <ResolvedRazorConfiguration Include="@(RazorConfiguration->WithMetadataValue('Identity', '$(RazorDefaultConfiguration)')->Distinct())" />
  </ItemGroup>
 
- <FindInList List="@(RazorExtension)" ItemSpecToFind="@(RazorConfiguration->Metadata('Extensions'))">
+ <FindInList List="@(RazorExtension)" ItemSpecToFind="@(ResolvedRazorConfiguration->Metadata('Extensions'))">
  <Output TaskParameter="ItemFound" ItemName="ResolvedRazorExtension" />
  </FindInList>
  </Target>

test/Microsoft.NET.Sdk.Razor.Test/IntegrationTests/BuildIntegrationTest.cs

@@ -630,6 +630,28 @@ public async Task Building_NETCoreApp21TargetingProject()
  Assert.FileExists(result, OutputPath, "SimpleMvc21.Views.pdb");
  }
 
+ [Fact]
+ [InitializeTestProject("SimpleMvc21")]
+ public async Task Building_WorksWhenMultipleRazorConfigurationsArePresent()
+ {
+ TargetFramework = "netcoreapp2.1";
+ AddProjectFileContent(@"
+<ItemGroup>
+ <RazorConfiguration Include=""MVC-2.1"">
+ <Extensions>MVC-2.1;$(CustomRazorExtension)</Extensions>
+ </RazorConfiguration>
+</ItemGroup>");
+
+ // Build
+ var result = await DotnetMSBuild("Build");
+
+ Assert.BuildPassed(result);
+ Assert.FileExists(result, OutputPath, "SimpleMvc21.dll");
+ Assert.FileExists(result, OutputPath, "SimpleMvc21.pdb");
+ Assert.FileExists(result, OutputPath, "SimpleMvc21.Views.dll");
+ Assert.FileExists(result, OutputPath, "SimpleMvc21.Views.pdb");
+ }
+
  private static DependencyContext ReadDependencyContext(string depsFilePath)
  {
  var reader = new DependencyContextJsonReader();

test/testapps/SimpleMvc21/SimpleMvc21.csproj

@@ -9,6 +9,8 @@
  <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>
 
+ <!-- Test Placeholder -->
+
  <PropertyGroup Condition="'$(RunningAsTest)' == ''">
  <!-- We don't want to run build server when not running as tests. -->
  <UseRazorBuildServer>false</UseRazorBuildServer>

test/testapps/SimpleMvc21/Views/_ViewImports.cshtml

@@ -1,3 +1,4 @@
 @using SimpleMvc
 @using SimpleMvc.Models
 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+@namespace SimpleMvc21