dotnet · JunTaoLuo · Jul 9, 2019 · Jul 10, 2019 · Jul 10, 2019 · Jul 11, 2019
diff --git a/docs/BuildFromSource.md b/docs/BuildFromSource.md
@@ -27,6 +27,7 @@ Building ASP.NET Core on Windows requires:
         ```ps1
         PS> ./eng/scripts/InstallJdk.ps1
         ```
+* Yarn <https://yarnpkg.com> is required if you are building JS components. For example, this may be required for building Components and SignalR.
 
 ### macOS/Linux
 
@@ -40,6 +41,7 @@ Building ASP.NET Core on macOS or Linux requires:
 * Java Development Kit 11 or newer. Either:
     * OpenJDK <https://jdk.java.net/>
     * Oracle's JDK <https://www.oracle.com/technetwork/java/javase/downloads/index.html>
+* Yarn <https://yarnpkg.com> is required if you are building JS components. For example, this may be required for building Components and SignalR.
 
 ## Clone the source code
 
@@ -129,6 +131,8 @@ On macOS/Linux:
 ./build.sh
 ```
 
+By default, only the C# projects are built. Some sub-areas have additional requirements, such as needing Yarn to be installed, before being able to build successfully.
+
 ### Using `dotnet` on command line in this repo
 
 Because we are using pre-release versions of .NET Core, you have to set a handful of environment variables

diff --git a/eng/Build.props b/eng/Build.props
@@ -31,6 +31,7 @@
                       $(RepoRoot)src\submodules\**\*.*proj;
                       $(RepoRoot)src\Installers\**\*.*proj;
                       $(RepoRoot)src\SignalR\clients\ts\**\node_modules\**\*.*proj;
+                      $(RepoRoot)src\Components\Web.JS\node_modules\**\*.*proj;
                       $(RepoRoot)src\Components\Blazor\Templates\src\content\**\*.*proj;
                       $(RepoRoot)src\ProjectTemplates\Web.ProjectTemplates\content\**\*.csproj;
                       $(RepoRoot)src\ProjectTemplates\Web.ProjectTemplates\content\**\*.fsproj;
@@ -103,6 +104,7 @@
 
         <NodeJsProjects Include="
                           $(RepoRoot)src\SignalR\**\*.npmproj;
+                          $(RepoRoot)src\Components\**\*.npmproj;
                           $(RepoRoot)src\Middleware\**\*.npmproj;
                           "
                         RestoreInParallel="false"

diff --git a/src/Components/Blazor/testassets/HostedInAspNet.Client/HostedInAspNet.Client.csproj b/src/Components/Blazor/testassets/HostedInAspNet.Client/HostedInAspNet.Client.csproj
@@ -3,12 +3,13 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <OutputType>Exe</OutputType>
-    <ReferenceBlazorBuildLocally>true</ReferenceBlazorBuildLocally>
+    <ReferenceBlazorBuildLocally Condition="'$(BuildNodeJS)' == 'true'">true</ReferenceBlazorBuildLocally>
     <RazorLangVersion>3.0</RazorLangVersion>
   </PropertyGroup>
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Blazor" />
+    <ProjectReference Include="$(RepoRoot)src\Components\Web.JS\Microsoft.AspNetCore.Components.Web.JS.npmproj" ReferenceOutputAssemblies="false" />
   </ItemGroup>
 
   <PropertyGroup>

diff --git a/...rosoft.AspNetCore.Blazor.E2EPerformance/Microsoft.AspNetCore.Blazor.E2EPerformance.csproj b/...rosoft.AspNetCore.Blazor.E2EPerformance/Microsoft.AspNetCore.Blazor.E2EPerformance.csproj
@@ -2,11 +2,12 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <ReferenceBlazorBuildLocally>true</ReferenceBlazorBuildLocally>
+    <ReferenceBlazorBuildLocally Condition="'$(BuildNodeJS)' == 'true'">true</ReferenceBlazorBuildLocally>
     <RazorLangVersion>3.0</RazorLangVersion>
   </PropertyGroup>
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Blazor" />
+    <ProjectReference Include="$(RepoRoot)src\Components\Web.JS\Microsoft.AspNetCore.Components.Web.JS.npmproj" ReferenceOutputAssemblies="false" />
   </ItemGroup>
 </Project>
diff --git a/src/Components/Blazor/testassets/MonoSanityClient/MonoSanityClient.csproj b/src/Components/Blazor/testassets/MonoSanityClient/MonoSanityClient.csproj
@@ -7,11 +7,12 @@
     <OutputType>exe</OutputType>
     <RazorLangVersion>3.0</RazorLangVersion>
 
-    <ReferenceBlazorBuildLocally>true</ReferenceBlazorBuildLocally>
+    <ReferenceBlazorBuildLocally Condition="'$(BuildNodeJS)' == 'true'">true</ReferenceBlazorBuildLocally>
     <!-- loader.js is hard-coded to assume it can load .pdbs regardless of Debug/Release configuration -->
     <BlazorEnableDebugging>true</BlazorEnableDebugging>
   </PropertyGroup>
 
   <ItemGroup>
+    <ProjectReference Include="$(RepoRoot)src\Components\Web.JS\Microsoft.AspNetCore.Components.Web.JS.npmproj" ReferenceOutputAssemblies="false" />
   </ItemGroup>
 </Project>
diff --git a/src/Components/Blazor/testassets/StandaloneApp/StandaloneApp.csproj b/src/Components/Blazor/testassets/StandaloneApp/StandaloneApp.csproj
@@ -2,12 +2,13 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <ReferenceBlazorBuildLocally>true</ReferenceBlazorBuildLocally>
+    <ReferenceBlazorBuildLocally Condition="'$(BuildNodeJS)' == 'true'">true</ReferenceBlazorBuildLocally>
     <RazorLangVersion>3.0</RazorLangVersion>
   </PropertyGroup>
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Blazor" />
     <Reference Include="Microsoft.AspNetCore.Blazor.HttpClient" />
+    <ProjectReference Include="$(RepoRoot)src\Components\Web.JS\Microsoft.AspNetCore.Components.Web.JS.npmproj" ReferenceOutputAssemblies="false" />
   </ItemGroup>
 </Project>
diff --git a/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj b/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj
@@ -20,6 +20,8 @@
     <Reference Include="Microsoft.Extensions.Caching.Memory" />
     <Reference Include="Microsoft.Extensions.FileProviders.Composite" />
     <Reference Include="Microsoft.Extensions.FileProviders.Embedded" />
+
+    <ProjectReference Include="..\..\Web.JS\Microsoft.AspNetCore.Components.Web.JS.npmproj" />
   </ItemGroup>
 
   <PropertyGroup>
@@ -51,17 +53,21 @@
   </ItemGroup>
 
   <PropertyGroup>
-    <!--
-      We check in the Release / Production build of blazor.*.js, but not the Debug builds. Consequently the former is always available to embed, the latter is only available
-      if Web.JS was built locally. Use the Debug build when available and building in Debug configuration.
-    -->
-    <BlazorServerJSFile>..\..\Web.JS\dist\Release\blazor.server.js</BlazorServerJSFile>
-    <BlazorServerJSFile Condition="'$(Configuration)' == 'Debug' AND Exists('..\..\Web.JS\dist\Debug\blazor.server.js')">..\..\Web.JS\dist\Debug\blazor.server.js</BlazorServerJSFile>
+    <BlazorServerJSFile>..\..\Web.JS\dist\$(Configuration)\blazor.server.js</BlazorServerJSFile>
   </PropertyGroup>
 
   <ItemGroup>
-    <EmbeddedResource Include="$(BlazorServerJSFile)" LogicalName="_framework/%(Filename)%(Extension)" />
+    <EmbeddedResource Include="$(BlazorServerJSFile)" LogicalName="_framework/%(Filename)%(Extension)" Condition="Exists('$(BlazorServerJSFile)')" />
     <EmbeddedResource Include="$(BlazorServerJSFile).map" LogicalName="_framework/%(Filename)%(Extension)" Condition="Exists('$(BlazorServerJSFile).map')" />
   </ItemGroup>
 
+  <Target Name="VerifyBlazorServerJSFileExists" BeforeTargets="PrepareForBuild">
+    <Warning
+      Text="Blazor server JS files not found and will not be embedded. Set BuildNodeJS to true or build the Microsoft.AspNetCore.Components.Web.JS.npmproj before building this project."
+      Condition="!Exists('$(BlazorServerJSFile)')" />
+    <Error
+      Text="Blazor server JS files not found and will not be embedded. Set BuildNodeJS to true or build the Microsoft.AspNetCore.Components.Web.JS.npmproj before building this project."
+      Condition="!Exists('$(BlazorServerJSFile)') and '$(Configuration)' == 'Release'" />
+  </Target>
+
 </Project>
diff --git a/src/Components/Web.JS/.gitignore b/src/Components/Web.JS/.gitignore
@@ -1,2 +1,2 @@
 node_modules/
-dist/Debug/
+dist/
diff --git a/src/Components/Web.JS/dist/.gitattributes b/src/Components/Web.JS/dist/.gitattributes
diff --git a/src/Components/Web.JS/dist/Release/blazor.server.js b/src/Components/Web.JS/dist/Release/blazor.server.js
diff --git a/src/Components/Web.JS/dist/Release/blazor.webassembly.js b/src/Components/Web.JS/dist/Release/blazor.webassembly.js
diff --git a/src/Components/test/testassets/BasicTestApp/BasicTestApp.csproj b/src/Components/test/testassets/BasicTestApp/BasicTestApp.csproj
@@ -4,7 +4,7 @@
     <TargetFramework>netstandard2.0</TargetFramework>
     <RazorLangVersion>3.0</RazorLangVersion>
 
-    <ReferenceBlazorBuildLocally>true</ReferenceBlazorBuildLocally>
+    <ReferenceBlazorBuildLocally Condition="'$(BuildNodeJS)' == 'true'">true</ReferenceBlazorBuildLocally>
     <!-- Must be defined before ReferenceFromSource.props is imported -->
     <AdditionalRunArguments>--pathbase /subdir</AdditionalRunArguments>
   </PropertyGroup>

diff --git a/src/Shared/E2ETesting/E2ETesting.targets b/src/Shared/E2ETesting/E2ETesting.targets
@@ -11,7 +11,7 @@
       Importance="High"
       Text="Prerequisites were not enforced at build time. Running Yarn or the E2E tests might fail as a result. Check /src/Shared/E2ETesting/Readme.md for instructions." />
 
-    <Yarn Command="install --mutex network" />
+    <Yarn Command="install --mutex network" Condition="'$(EnforceE2ETestPrerequisites)' == 'true'"/>
   </Target>
 
   <Target