Tidy up build filesystem providers code

src/Microsoft.Blazor.BuildTools/Core/Build.cs

@@ -1,6 +1,7 @@
 // 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 Microsoft.Blazor.BuildTools.Core.FileSystem;
 using System.IO;
 
 namespace Microsoft.Blazor.BuildTools.Core
@@ -9,7 +10,7 @@ namespace Microsoft.Blazor.BuildTools.Core
     {
         internal static void Execute(string assemblyPath, string webRootPath)
         {
-            var clientFileSystem = ClientFileSystem.Instantiate(assemblyPath, webRootPath);
+            var clientFileSystem = new ClientFileProvider(assemblyPath, webRootPath);
             var distDirPath = Path.Combine(Path.GetDirectoryName(assemblyPath), "dist");
             FileUtil.WriteFileProviderToDisk(clientFileSystem, distDirPath, clean: true);
         }

src/Microsoft.Blazor.BuildTools/Core/ClientFileSystem.cs

@@ -1,45 +0,0 @@
-// 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 Microsoft.Blazor.BuildTools.Core.FrameworkFiles;
-using Microsoft.Blazor.BuildTools.Core.WebRootFiles;
-using Microsoft.Blazor.Internal.Common.FileProviders;
-using Microsoft.Extensions.FileProviders;
-using System.Collections.Generic;
-using System.IO;
-
-namespace Microsoft.Blazor.BuildTools.Core
-{
-    internal static class ClientFileSystem
-    {
-        public static IFileProvider Instantiate(string clientAssemblyPath, string webRootPath)
-        {
-            var fileProviders = new List<(string, IFileProvider)>();
-
-            if (!File.Exists(clientAssemblyPath))
-            {
-                throw new FileNotFoundException($"Could not find client assembly file at '{clientAssemblyPath}'.", clientAssemblyPath);
-            }
-
-            var frameworkFileProvider = FrameworkFileProvider.Instantiate(
-                clientAssemblyPath);
-            fileProviders.Add(("/_framework", frameworkFileProvider));
-
-            if (!string.IsNullOrEmpty(webRootPath))
-            {
-                if (!Directory.Exists(webRootPath))
-                {
-                    throw new DirectoryNotFoundException($"Could not find web root directory at '{webRootPath}'.");
-                }
-
-                var webRootFileProvider = WebRootFileProvider.Instantiate(
-                    webRootPath,
-                    Path.GetFileNameWithoutExtension(clientAssemblyPath),
-                    frameworkFileProvider.GetDirectoryContents("/_bin"));
-                fileProviders.Add(("/", webRootFileProvider));
-            }
-
-            return new CompositeMountedFileProvider(fileProviders.ToArray());
-        }
-    }
-}

src/Microsoft.Blazor.BuildTools/Core/FileSystem/ClientFileProvider.cs

@@ -0,0 +1,63 @@
+// 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 Microsoft.Blazor.Internal.Common.FileProviders;
+using Microsoft.Extensions.FileProviders;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Microsoft.Blazor.BuildTools.Core.FileSystem
+{
+    internal class ClientFileProvider : CompositeMountedFileProvider
+    {
+        public ClientFileProvider(string clientAssemblyPath, string webRootPath)
+            : base(GetContents(clientAssemblyPath, webRootPath))
+        {
+        }
+
+        private static (string, IFileProvider)[] GetContents(string clientAssemblyPath, string webRootPath)
+        {
+            var fileProviders = new List<(string, IFileProvider)>();
+
+            // There must always be a client assembly, and we always supply a /_framework
+            // directory containing everything needed to execute it
+            if (!File.Exists(clientAssemblyPath))
+            {
+                throw new FileNotFoundException($"Could not find client assembly file at '{clientAssemblyPath}'.", clientAssemblyPath);
+            }
+            var frameworkFileProvider = new FrameworkFileProvider(clientAssemblyPath);
+            fileProviders.Add(("/_framework", frameworkFileProvider));
+            
+            // The web root directory is optional. If it exists and contains /index.html, then
+            // we will inject the relevant <script> tag and supply that file. Otherwise, we just
+            // don't supply an /index.html file.
+            if (TryCreateIndexHtmlFileProvider(
+                webRootPath, clientAssemblyPath, frameworkFileProvider, out var indexHtmlFileProvider))
+            {
+                fileProviders.Add(("/", indexHtmlFileProvider));
+            }
+
+            return fileProviders.ToArray();
+        }
+
+        private static bool TryCreateIndexHtmlFileProvider(
+            string webRootPath, string assemblyPath, IFileProvider frameworkFileProvider, out IFileProvider result)
+        {
+            if (!string.IsNullOrEmpty(webRootPath))
+            {
+                var path = Path.Combine(webRootPath, "index.html");
+                if (File.Exists(path))
+                {
+                    var template = File.ReadAllText(path);
+                    var assemblyName = Path.GetFileNameWithoutExtension(assemblyPath);
+                    var binFiles = frameworkFileProvider.GetDirectoryContents("/_bin");
+                    result = new IndexHtmlFileProvider(template, assemblyName, binFiles);
+                    return true;
+                }
+            }
+
+            result = null;
+            return false;
+        }
+    }
+}

src/Microsoft.Blazor.BuildTools/Core/FileSystem/FrameworkFiles/FrameworkFileProvider.cs

@@ -7,17 +7,26 @@ using Microsoft.Blazor.Mono;
 using Microsoft.Extensions.FileProviders;
 using System.IO;
 
-namespace Microsoft.Blazor.BuildTools.Core.FrameworkFiles
+namespace Microsoft.Blazor.BuildTools.Core.FileSystem
 {
-    internal static class FrameworkFileProvider
+    internal class FrameworkFileProvider : CompositeMountedFileProvider
     {
-        public static IFileProvider Instantiate(string clientAssemblyPath)
+        public FrameworkFileProvider(string clientAssemblyPath)
-            => new CompositeMountedFileProvider(
+            : base(GetContents(clientAssemblyPath))
+        {
+        }
+
+        private static (string, IFileProvider)[] GetContents(string clientAssemblyPath)
+        {
+            return new[]
+            {
                 ("/", MonoStaticFileProvider.JsFiles),
                 ("/", BlazorBrowserFileProvider.Instance),
-                ("/_bin", BinDirFileProvider(clientAssemblyPath)));
+                ("/_bin", CreateBinDirFileProvider(clientAssemblyPath))
+            };
+        }
 
-        private static IFileProvider BinDirFileProvider(string clientAssemblyPath)
+        private static IFileProvider CreateBinDirFileProvider(string clientAssemblyPath)
             => new ReferencedAssemblyFileProvider(
                     Path.GetFileNameWithoutExtension(clientAssemblyPath),
                     new ReferencedAssemblyResolver(

src/Microsoft.Blazor.BuildTools/Core/FileSystem/FrameworkFiles/ReferencedAssemblyFileProvider.cs

@@ -7,7 +7,7 @@ using System.Linq;
 using Mono.Cecil;
 using Microsoft.Blazor.Internal.Common.FileProviders;
 
-namespace Microsoft.Blazor.BuildTools.Core.FrameworkFiles
+namespace Microsoft.Blazor.BuildTools.Core.FileSystem
 {
     internal class ReferencedAssemblyFileProvider : InMemoryFileProvider
     {

src/Microsoft.Blazor.BuildTools/Core/FileSystem/FrameworkFiles/ReferencedAssemblyResolver.cs

@@ -5,7 +5,7 @@ using Microsoft.Extensions.FileProviders;
 using System.IO;
 using System.Linq;
 
-namespace Microsoft.Blazor.BuildTools.Core.FrameworkFiles
+namespace Microsoft.Blazor.BuildTools.Core.FileSystem
 {
     internal class ReferencedAssemblyResolver
     {

src/Microsoft.Blazor.BuildTools/Core/FileSystem/IndexHtmlFileProvider.cs

@@ -8,7 +8,7 @@ using System.Text;
 using Microsoft.Extensions.FileProviders;
 using System.Linq;
 
-namespace Microsoft.Blazor.BuildTools.Core.WebRootFiles
+namespace Microsoft.Blazor.BuildTools.Core.FileSystem
 {
     internal class IndexHtmlFileProvider : InMemoryFileProvider
     {

src/Microsoft.Blazor.BuildTools/Core/WebRootFiles/WebRootFileProvider.cs

@@ -1,25 +0,0 @@
-// 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 Microsoft.Extensions.FileProviders;
-using System.Collections.Generic;
-using System.IO;
-
-namespace Microsoft.Blazor.BuildTools.Core.WebRootFiles
-{
-    internal static class WebRootFileProvider
-    {
-        public static IFileProvider Instantiate(
-            string clientWebRoot, string assemblyName, IEnumerable<IFileInfo> binFiles)
-            => new CompositeFileProvider(
-                new IndexHtmlFileProvider(
-                    ReadIndexHtmlFile(clientWebRoot), assemblyName, binFiles),
-                new PhysicalFileProvider(clientWebRoot));
-
-        private static string ReadIndexHtmlFile(string clientWebRoot)
-        {
-            var path = Path.Combine(clientWebRoot, "index.html");
-            return File.Exists(path) ? File.ReadAllText(path) : null;
-        }
-    }
-}

test/Microsoft.Blazor.Build.Test/IndexHtmlFileProviderTest.cs

@@ -7,7 +7,7 @@ using System.Linq;
 using Xunit;
 using System;
 using AngleSharp.Parser.Html;
-using Microsoft.Blazor.BuildTools.Core.WebRootFiles;
+using Microsoft.Blazor.BuildTools.Core.FileSystem;
 
 namespace Microsoft.Blazor.Server.Test
 {

test/Microsoft.Blazor.Build.Test/ReferencedAssemblyFileProviderTest.cs

@@ -1,7 +1,7 @@
 // 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 Microsoft.Blazor.BuildTools.Core.FrameworkFiles;
+using Microsoft.Blazor.BuildTools.Core.FileSystem;
 using Microsoft.Blazor.Mono;
 using Mono.Cecil;
 using System;