Add support for <BlazorWebAssemblyLazyLoad /> item group (#23071)

* Add support for <BlazorLazyLoad /> item group
* Respond to feedback from peer review

src/Components/WebAssembly/Build/src/Tasks/GenerateBlazorBootJson.cs

@@ -88,6 +88,9 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
                         case "assembly":
                             resourceList = resourceData.assembly;
                             break;
+                        case "dynamicAssembly":
+                            resourceList = resourceData.dynamicAssembly;
+                            break;
                         case "pdb":
                             resourceData.pdb ??= new ResourceHashesByNameDictionary();
                             resourceList = resourceData.pdb;
@@ -207,6 +210,11 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
             /// </summary>
             public ResourceHashesByNameDictionary assembly { get; set; } = new ResourceHashesByNameDictionary();
 
+            /// <summary>
+            /// Assembly (.dll) resources that are loaded dynamically during runtime
+            /// </summary>
+            public ResourceHashesByNameDictionary dynamicAssembly { get; set; } = new ResourceHashesByNameDictionary();
+
             /// <summary>
             /// "debug" (.pdb) resources
             /// </summary>

src/Components/WebAssembly/Build/src/targets/Blazor.MonoRuntime.targets

@@ -129,6 +129,7 @@
       <_BlazorOutputWithTargetPath Include="@(_BlazorResolvedAssembly)">
         <BootManifestResourceType Condition="'%(Extension)' == '.dll'">assembly</BootManifestResourceType>
         <BootManifestResourceType Condition="'%(Extension)' == '.pdb'">pdb</BootManifestResourceType>
+        <BootManifestResourceType Condition="@(BlazorWebAssemblyLazyLoad->AnyHaveMetadataValue('Identity', '%(Filename)')) != ''">dynamicAssembly</BootManifestResourceType>
         <BootManifestResourceName>%(FileName)%(Extension)</BootManifestResourceName>
         <TargetOutputPath>$(_BlazorRuntimeBinOutputPath)%(FileName)%(Extension)</TargetOutputPath>
       </_BlazorOutputWithTargetPath>

src/Components/WebAssembly/Build/test/BuildIntegrationTests/BuildLazyLoadTest.cs

@@ -0,0 +1,176 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Testing;
+using Xunit;
+using static Microsoft.AspNetCore.Components.WebAssembly.Build.WebAssemblyRuntimePackage;
+
+namespace Microsoft.AspNetCore.Components.WebAssembly.Build
+{
+    public class BuildLazyLoadTest
+    {
+        [Fact]
+        public async Task Build_LazyLoadExplicitAssembly_Debug_Works()
+        {
+            // Arrange
+            using var project = ProjectDirectory.Create("standalone", additionalProjects: new[] { "razorclasslibrary" });
+            project.Configuration = "Debug";
+
+            project.AddProjectFileContent(
+@"
+<ItemGroup>
+    <BlazorWebAssemblyLazyLoad Include='RazorClassLibrary.dll' />
+</ItemGroup>
+");
+
+            var result = await MSBuildProcessManager.DotnetMSBuild(project);
+
+            var buildOutputDirectory = project.BuildOutputDirectory;
+
+            // Verify that a blazor.boot.json file has been created
+            Assert.FileExists(result, buildOutputDirectory, "wwwroot", "_framework", "blazor.boot.json");
+            // And that the assembly is in the output
+            Assert.FileExists(result, buildOutputDirectory, "wwwroot", "_framework", "_bin", "RazorClassLibrary.dll");
+
+            var bootJson = ReadBootJsonData(result, Path.Combine(buildOutputDirectory, "wwwroot", "_framework", "blazor.boot.json"));
+
+            // And that it has been labelled as a dynamic assembly in the boot.json
+            var dynamicAssemblies = bootJson.resources.dynamicAssembly;
+            var assemblies = bootJson.resources.assembly;
+
+            Assert.NotNull(dynamicAssemblies);
+            Assert.Contains("RazorClassLibrary.dll", dynamicAssemblies.Keys);
+            Assert.DoesNotContain("RazorClassLibrary.dll", assemblies.Keys);
+
+            // App assembly should not be lazy loaded
+            Assert.DoesNotContain("standalone.dll", dynamicAssemblies.Keys);
+            Assert.Contains("standalone.dll", assemblies.Keys);
+        }
+
+        [Fact]
+        public async Task Build_LazyLoadExplicitAssembly_Release_Works()
+        {
+            // Arrange
+            using var project = ProjectDirectory.Create("standalone", additionalProjects: new[] { "razorclasslibrary" });
+            project.Configuration = "Release";
+
+            project.AddProjectFileContent(
+@"
+<ItemGroup>
+    <BlazorWebAssemblyLazyLoad Include='RazorClassLibrary.dll' />
+</ItemGroup>
+");
+
+            var result = await MSBuildProcessManager.DotnetMSBuild(project);
+
+            var buildOutputDirectory = project.BuildOutputDirectory;
+
+            // Verify that a blazor.boot.json file has been created
+            Assert.FileExists(result, buildOutputDirectory, "wwwroot", "_framework", "blazor.boot.json");
+            // And that the assembly is in the output
+            Assert.FileExists(result, buildOutputDirectory, "wwwroot", "_framework", "_bin", "RazorClassLibrary.dll");
+
+            var bootJson = ReadBootJsonData(result, Path.Combine(buildOutputDirectory, "wwwroot", "_framework", "blazor.boot.json"));
+
+            // And that it has been labelled as a dynamic assembly in the boot.json
+            var dynamicAssemblies = bootJson.resources.dynamicAssembly;
+            var assemblies = bootJson.resources.assembly;
+
+            Assert.NotNull(dynamicAssemblies);
+            Assert.Contains("RazorClassLibrary.dll", dynamicAssemblies.Keys);
+            Assert.DoesNotContain("RazorClassLibrary.dll", assemblies.Keys);
+
+            // App assembly should not be lazy loaded
+            Assert.DoesNotContain("standalone.dll", dynamicAssemblies.Keys);
+            Assert.Contains("standalone.dll", assemblies.Keys);
+        }
+
+                [Fact]
+        public async Task Publish_LazyLoadExplicitAssembly_Debug_Works()
+        {
+            // Arrange
+            using var project = ProjectDirectory.Create("standalone", additionalProjects: new[] { "razorclasslibrary" });
+            project.Configuration = "Debug";
+
+            project.AddProjectFileContent(
+@"
+<ItemGroup>
+    <BlazorWebAssemblyLazyLoad Include='RazorClassLibrary.dll' />
+</ItemGroup>
+");
+
+            var result = await MSBuildProcessManager.DotnetMSBuild(project, "Publish");
+
+            var publishDirectory = project.PublishOutputDirectory;
+
+            // Verify that a blazor.boot.json file has been created
+            Assert.FileExists(result, publishDirectory, "wwwroot", "_framework", "blazor.boot.json");
+            // And that the assembly is in the output
+            Assert.FileExists(result, publishDirectory, "wwwroot", "_framework", "_bin", "RazorClassLibrary.dll");
+
+            var bootJson = ReadBootJsonData(result, Path.Combine(publishDirectory, "wwwroot", "_framework", "blazor.boot.json"));
+
+            // And that it has been labelled as a dynamic assembly in the boot.json
+            var dynamicAssemblies = bootJson.resources.dynamicAssembly;
+            var assemblies = bootJson.resources.assembly;
+
+            Assert.NotNull(dynamicAssemblies);
+            Assert.Contains("RazorClassLibrary.dll", dynamicAssemblies.Keys);
+            Assert.DoesNotContain("RazorClassLibrary.dll", assemblies.Keys);
+
+            // App assembly should not be lazy loaded
+            Assert.DoesNotContain("standalone.dll", dynamicAssemblies.Keys);
+            Assert.Contains("standalone.dll", assemblies.Keys);
+        }
+
+        [Fact]
+        public async Task Publish_LazyLoadExplicitAssembly_Release_Works()
+        {
+            // Arrange
+            using var project = ProjectDirectory.Create("standalone", additionalProjects: new[] { "razorclasslibrary" });
+            project.Configuration = "Release";
+
+            project.AddProjectFileContent(
+@"
+<ItemGroup>
+    <BlazorWebAssemblyLazyLoad Include='RazorClassLibrary.dll' />
+</ItemGroup>
+");
+
+            var result = await MSBuildProcessManager.DotnetMSBuild(project, "Publish");
+
+            var publishDirectory = project.PublishOutputDirectory;
+
+            // Verify that a blazor.boot.json file has been created
+            Assert.FileExists(result, publishDirectory, "wwwroot", "_framework", "blazor.boot.json");
+            // And that the assembly is in the output
+            Assert.FileExists(result, publishDirectory, "wwwroot", "_framework", "_bin", "RazorClassLibrary.dll");
+
+            var bootJson = ReadBootJsonData(result, Path.Combine(publishDirectory, "wwwroot", "_framework", "blazor.boot.json"));
+
+            // And that it has been labelled as a dynamic assembly in the boot.json
+            var dynamicAssemblies = bootJson.resources.dynamicAssembly;
+            var assemblies = bootJson.resources.assembly;
+
+            Assert.NotNull(dynamicAssemblies);
+            Assert.Contains("RazorClassLibrary.dll", dynamicAssemblies.Keys);
+            Assert.DoesNotContain("RazorClassLibrary.dll", assemblies.Keys);
+
+            // App assembly should not be lazy loaded
+            Assert.DoesNotContain("standalone.dll", dynamicAssemblies.Keys);
+            Assert.Contains("standalone.dll", assemblies.Keys);
+        }
+
+        private static GenerateBlazorBootJson.BootJsonData ReadBootJsonData(MSBuildResult result, string path)
+        {
+            return JsonSerializer.Deserialize<GenerateBlazorBootJson.BootJsonData>(
+                File.ReadAllText(Path.Combine(result.Project.DirectoryPath, path)),
+                new JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+        }
+    }
+}