[browser] Expect fingerprint on dotnet.js for preloading (#120694)

Author: maraf

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

@@ -566,8 +566,13 @@ Copyright (c) .NET Foundation. All rights reserved.
   </Target>
 
   <Target Name="_AddWasmPreloadBuildProperties" DependsOnTargets="_WasmConfigurePreload;_AddWasmStaticWebAssets" BeforeTargets="GenerateStaticWebAssetsManifest" Condition="'$(_WasmPreloadAssets)' == 'true'">
+    <PropertyGroup>
+      <_WasmBootConfigFileNameWithoutExtension>$([System.IO.Path]::GetFileNameWithoutExtension('$(_WasmBootConfigFileName)'))</_WasmBootConfigFileNameWithoutExtension>
+      <_WasmBootConfigFileExtension>$([System.IO.Path]::GetExtension('$(_WasmBootConfigFileName)'))</_WasmBootConfigFileExtension>
+    </PropertyGroup>
     <ItemGroup>
-      <_WasmPreloadBuildScriptAsset Include="@(StaticWebAsset)" Condition="'%(AssetKind)' != 'Publish' and '%(FileName)%(Extension)' == '$(_WasmBootConfigFileName)'" />
+      <_WasmPreloadBuildScriptAsset Include="@(StaticWebAsset)" Condition="'$(_WasmFingerprintAssets)' == 'true' and '$(_WasmFingerprintBootConfig)' == 'true' and '%(AssetKind)' != 'Publish' and '%(FileName)%(Extension)' == '$(_WasmBootConfigFileNameWithoutExtension).%(Fingerprint)$(_WasmBootConfigFileExtension)'" />
+      <_WasmPreloadBuildScriptAsset Include="@(StaticWebAsset)" Condition="('$(_WasmFingerprintAssets)' != 'true' or '$(_WasmFingerprintBootConfig)' != 'true') and '%(AssetKind)' != 'Publish' and '%(FileName)%(Extension)' == '$(_WasmBootConfigFileName)'" />
     </ItemGroup>
 
     <FilterStaticWebAssetEndpoints

src/mono/wasm/Wasm.Build.Tests/PreloadingTests.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.IO;
 using System.Linq;
 using Xunit;
@@ -18,22 +19,26 @@ public PreloadingTests(ITestOutputHelper output, SharedBuildPerTestClassFixture
     }
 
     [Theory]
-    [InlineData(false, false)]
-    [InlineData(false, true)]
-    [InlineData(true, false)]
-    [InlineData(true, true)]
-    public void PreloadAssets(bool isPublish, bool fingerprintDotnetJs)
+    [InlineData(false, false, false)]
+    [InlineData(false, false, true)]
+    [InlineData(false, true, false)]
+    [InlineData(false, true, true)]
+    [InlineData(true, false, false)]
+    [InlineData(true, false, true)]
+    [InlineData(true, true, false)]
+    [InlineData(true, true, true)]
+    public void PreloadAssets(bool isPublish, bool fingerprintDotnetJs, bool preloadAssets)
     {
         Configuration config = Configuration.Debug;
         ProjectInfo info = CopyTestAsset(config, aot: false, TestAsset.WasmBasicTestApp, "PreloadAssets");
 
-        string extraMSBuildArgs = $"-p:WasmFingerprintDotnetJs={fingerprintDotnetJs}";
+        string extraMSBuildArgs = $"-p:WasmFingerprintDotnetJs={fingerprintDotnetJs.ToString().ToLower()} -p:WasmPreloadAssets={preloadAssets.ToString().ToLower()}";
         if (isPublish)
             PublishProject(info, config, new PublishOptions(ExtraMSBuildArgs: extraMSBuildArgs), wasmFingerprintDotnetJs: fingerprintDotnetJs);
         else
             BuildProject(info, config, new BuildOptions(ExtraMSBuildArgs: extraMSBuildArgs), wasmFingerprintDotnetJs: fingerprintDotnetJs);
 
-        string? indexHtmlPath = null;
+        string? indexHtmlPath;
         if (isPublish)
         {
             indexHtmlPath = Path.Combine(
@@ -51,16 +56,37 @@ public void PreloadAssets(bool isPublish, bool fingerprintDotnetJs)
         Assert.True(File.Exists(indexHtmlPath));
         string indexHtmlContent = File.ReadAllText(indexHtmlPath);
 
-        if (fingerprintDotnetJs)
+        Assert.Equal(preloadAssets ? 1 : 0, CountOccurrences(indexHtmlContent, "rel=\"preload\""));
+        if (preloadAssets)
         {
-            // Expect to find fingerprinted preload
-            Assert.Contains("<link href=\"_framework/dotnet", indexHtmlContent);
-            Assert.DoesNotContain("<link href=\"_framework/dotnet.js\"", indexHtmlContent);
+            if (fingerprintDotnetJs)
+            {
+                // Expect to find fingerprinted preload
+                Assert.Contains("<link href=\"_framework/dotnet", indexHtmlContent);
+                Assert.DoesNotContain("<link href=\"_framework/dotnet.js\"", indexHtmlContent);
+            }
+            else
+            {
+                // Expect to find non-fingerprinted preload
+                Assert.Contains("<link href=\"_framework/dotnet.js\"", indexHtmlContent);
+            }
         }
-        else
+    }
+
+    public static int CountOccurrences(string source, string substring)
+    {
+        if (string.IsNullOrEmpty(source) || string.IsNullOrEmpty(substring))
+            return 0;
+
+        int count = 0;
+        int index = 0;
+
+        while ((index = source.IndexOf(substring, index, StringComparison.Ordinal)) != -1)
         {
-            // Expect to find non-fingerprinted preload
-            Assert.Contains("<link href=\"_framework/dotnet.js\"", indexHtmlContent);
+            count++;
+            index += substring.Length;
         }
+
+        return count;
     }
 }