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Generate deterministic Blazor asset manifest to fix universal builds
The bundled fingerprint manifest was the SDK's raw static web assets endpoints manifest, which embeds volatile per-file data (Last-Modified timestamps). On a universal MacCatalyst build the x64 and arm64 legs produce byte-different manifests, so the SDK's app-bundle merge fails: error : Unable to merge the file 'Contents/Resources/_maui/blazor-asset-manifest.json', it's different between the input app bundles. This broke every Blazor Hybrid template build on macOS (BlazorTemplateTest and SimpleTemplateTest with the maui-blazor template). Single-RID device tests never hit the universal merge, so it wasn't caught locally. Instead of bundling the raw manifest, generate a minimal manifest from the @(StaticWebAssetEndpoint) items at build time containing only the fingerprinted route and its logical label. That data is entirely content-derived (fingerprints are content hashes, labels are logical names) with no timestamps, absolute paths, or RIDs, and is emitted sorted - so it is byte-identical across architectures and the universal merge succeeds. Verified: the x64 and arm64 manifests now have an identical SHA-256. Also simplifies the runtime: it now parses a tiny purpose-built file (via STJ source-gen) instead of walking the large SDK endpoints manifest. MacCatalyst device tests: 45 passed, 1 pre-existing skip, including AppTypeResolvesFingerprintedAssetsViaAssets. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 2ca68fe1-bef6-46a6-a0fd-17b7654cef34
1 parent fb24f61 commit c46e8d4

2 files changed

Lines changed: 120 additions & 102 deletions

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‎src/BlazorWebView/src/Maui/StaticWebAssetsManifest.cs‎

Lines changed: 26 additions & 96 deletions
Original file line numberDiff line numberDiff line change
@@ -10,18 +10,20 @@
1010
namespace Microsoft.AspNetCore.Components.WebView.Maui
1111
{
1212
/// <summary>
13-
/// Parses the static web assets endpoints manifest (<c>*.staticwebassets.endpoints.json</c>) that
14-
/// is bundled with a hybrid app and exposes it as:
13+
/// Loads the minimal fingerprinted-asset manifest that MAUI generates at build time (from the
14+
/// static web assets endpoints) and bundles with a hybrid app, and exposes it as:
1515
/// <list type="bullet">
1616
/// <item><description>a <see cref="ResourceAssetCollection"/> so <c>@Assets["logical"]</c> resolves to the
1717
/// fingerprinted URL at render time; and</description></item>
1818
/// <item><description>a route-to-physical map so the web view can serve the physical asset for a
1919
/// fingerprinted request URL.</description></item>
2020
/// </list>
2121
/// Blazor Web Apps build this from endpoint metadata via <c>MapStaticAssets</c>; hybrid apps have no
22-
/// server, so this reconstructs the same information from the bundled manifest. The manifest is
23-
/// bundled outside the web root and read via the app package APIs, so it is never exposed to the
24-
/// web view.
22+
/// server, so MAUI reconstructs just the fingerprint mapping at build time. The manifest is bundled
23+
/// outside the web root and read via the app package APIs, so it is never exposed to the web view.
24+
/// Its content is derived entirely from asset fingerprints and logical names (no timestamps, absolute
25+
/// paths, or runtime identifiers), so it is deterministic and identical across architectures - which
26+
/// is required for universal (multi-RID) app bundles to merge.
2527
/// </summary>
2628
internal sealed class StaticWebAssetsManifest
2729
{
@@ -41,7 +43,7 @@ private StaticWebAssetsManifest(ResourceAssetCollection assets, IReadOnlyDiction
4143
/// <summary>Gets the fingerprint-aware asset collection used to resolve <c>@Assets</c>.</summary>
4244
public ResourceAssetCollection Assets { get; }
4345

44-
/// <summary>Gets the map of request route (possibly fingerprinted) to the physical asset file.</summary>
46+
/// <summary>Gets the map of fingerprinted request route to the physical asset file under the web root.</summary>
4547
public IReadOnlyDictionary<string, string> RouteToPhysicalPath { get; }
4648

4749
/// <summary>
@@ -84,53 +86,28 @@ internal static StaticWebAssetsManifest Parse(Stream stream)
8486
internal static StaticWebAssetsManifest FromData(ManifestData? data)
8587
{
8688
var resources = new List<ResourceAsset>();
87-
var seenLabels = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
8889
var routeToPhysical = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
8990

90-
var endpoints = data?.Endpoints;
91-
if (endpoints is null || endpoints.Count == 0)
91+
var assets = data?.Assets;
92+
if (assets is null || assets.Count == 0)
9293
{
9394
return new StaticWebAssetsManifest(ResourceAssetCollection.Empty, routeToPhysical);
9495
}
9596

96-
foreach (var endpoint in endpoints)
97+
foreach (var asset in assets)
9798
{
98-
var route = endpoint.Route;
99-
var assetFile = endpoint.AssetFile;
100-
if (route is null || assetFile is null)
99+
var route = asset.Route;
100+
var label = asset.Label;
101+
if (route is null || label is null)
101102
{
102103
continue;
103104
}
104105

105-
// Endpoints with selectors are alternative representations (for example gzip/brotli
106-
// content negotiation). They are not distinct assets, so skip them - mirroring the
107-
// framework's own ResourceCollectionResolver.
108-
if (endpoint.Selectors is { Count: > 0 })
109-
{
110-
continue;
111-
}
112-
113-
var isCompressed = assetFile.EndsWith(".gz", StringComparison.OrdinalIgnoreCase) ||
114-
assetFile.EndsWith(".br", StringComparison.OrdinalIgnoreCase);
115-
116-
var (label, integrity) = ReadProperties(endpoint.EndpointProperties);
117-
118-
// @Assets resolution: map the human-readable label to the fingerprinted route. Skip
119-
// compressed variants and duplicate labels to avoid collisions.
120-
if (label is not null && !isCompressed && seenLabels.Add(label))
121-
{
122-
var properties = integrity is null
123-
? new[] { new ResourceAssetProperty("label", label) }
124-
: new[] { new ResourceAssetProperty("label", label), new ResourceAssetProperty("integrity", integrity) };
125-
resources.Add(new ResourceAsset(route, properties));
126-
}
106+
// @Assets resolution: the fingerprinted route is exposed under its logical label.
107+
resources.Add(new ResourceAsset(route, new[] { new ResourceAssetProperty("label", label) }));
127108

128-
// Serving: map the (possibly fingerprinted) route to the physical file on disk. Prefer
129-
// the uncompressed asset and keep the first mapping for a given route.
130-
if (!isCompressed)
131-
{
132-
routeToPhysical.TryAdd(NormalizePath(route), NormalizePath(assetFile));
133-
}
109+
// Serving: the physical file under the web root is the logical (non-fingerprinted) label.
110+
routeToPhysical.TryAdd(NormalizePath(route), NormalizePath(label));
134111
}
135112

136113
return new StaticWebAssetsManifest(new ResourceAssetCollection(resources), routeToPhysical);
@@ -157,72 +134,25 @@ public bool TryResolvePhysicalPath(string requestedPath, out string physicalPath
157134
return false;
158135
}
159136

160-
private static (string? Label, string? Integrity) ReadProperties(List<EndpointProperty>? properties)
161-
{
162-
string? label = null;
163-
string? integrity = null;
164-
165-
if (properties is not null)
166-
{
167-
foreach (var property in properties)
168-
{
169-
if (property.Name is null)
170-
{
171-
continue;
172-
}
173-
174-
if (label is null && property.Name.Equals("label", StringComparison.OrdinalIgnoreCase))
175-
{
176-
label = property.Value;
177-
}
178-
else if (integrity is null && property.Name.Equals("integrity", StringComparison.OrdinalIgnoreCase))
179-
{
180-
integrity = property.Value;
181-
}
182-
}
183-
}
184-
185-
return (label, integrity);
186-
}
187-
188137
private static string NormalizePath(string path) =>
189138
(path ?? string.Empty).Replace('\\', '/').TrimStart('/');
190139

191-
/// <summary>The subset of the endpoints manifest that hybrid asset resolution needs.</summary>
140+
/// <summary>The minimal fingerprint manifest MAUI generates at build time.</summary>
192141
internal sealed class ManifestData
193142
{
194-
[JsonPropertyName("Endpoints")]
195-
public List<Endpoint>? Endpoints { get; set; }
143+
[JsonPropertyName("Assets")]
144+
public List<AssetEntry>? Assets { get; set; }
196145
}
197146

198-
internal sealed class Endpoint
147+
internal sealed class AssetEntry
199148
{
149+
/// <summary>The fingerprinted, served route (for example <c>_content/Pkg/app.abc123.css</c>).</summary>
200150
[JsonPropertyName("Route")]
201151
public string? Route { get; set; }
202152

203-
[JsonPropertyName("AssetFile")]
204-
public string? AssetFile { get; set; }
205-
206-
[JsonPropertyName("Selectors")]
207-
public List<EndpointSelector>? Selectors { get; set; }
208-
209-
[JsonPropertyName("EndpointProperties")]
210-
public List<EndpointProperty>? EndpointProperties { get; set; }
211-
}
212-
213-
internal sealed class EndpointSelector
214-
{
215-
[JsonPropertyName("Name")]
216-
public string? Name { get; set; }
217-
}
218-
219-
internal sealed class EndpointProperty
220-
{
221-
[JsonPropertyName("Name")]
222-
public string? Name { get; set; }
223-
224-
[JsonPropertyName("Value")]
225-
public string? Value { get; set; }
153+
/// <summary>The logical, non-fingerprinted path used by <c>@Assets</c> and stored on disk under the web root.</summary>
154+
[JsonPropertyName("Label")]
155+
public string? Label { get; set; }
226156
}
227157
}
228158

‎src/BlazorWebView/src/Maui/build/Microsoft.AspNetCore.Components.WebView.Maui.targets‎

Lines changed: 94 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -70,17 +70,105 @@
7070
</Target>
7171

7272
<!--
73-
Bundle the static web assets endpoints manifest so that fingerprinted assets (@Assets, @ImportMap)
73+
Generate a minimal, deterministic fingerprint manifest so that fingerprinted assets (@Assets)
7474
can be resolved at runtime. Blazor Web Apps get this from MapStaticAssets endpoint metadata; hybrid
75-
apps have no server, so BlazorWebView loads this bundled manifest instead. It is bundled OUTSIDE
76-
wwwroot so it is never exposed to the web view, and BlazorWebView reads it from the app package via
77-
FileSystem.OpenAppPackageFileAsync.
75+
apps have no server, so MAUI reconstructs just the fingerprint mapping (fingerprinted route -> logical
76+
label) from the static web asset endpoints.
77+
78+
The generated file is bundled OUTSIDE wwwroot so it is never exposed to the web view, and BlazorWebView
79+
reads it from the app package via FileSystem.OpenAppPackageFileAsync. Its content is derived entirely
80+
from content fingerprints and logical names (no timestamps, absolute paths, or RIDs), so it is byte
81+
identical across architectures - which the SDK requires when merging universal (multi-RID) app bundles.
7882
-->
83+
<UsingTask TaskName="_GenerateMauiBlazorAssetManifest"
84+
TaskFactory="RoslynCodeTaskFactory"
85+
AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll">
86+
<ParameterGroup>
87+
<Endpoints ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true" />
88+
<OutputFile ParameterType="System.String" Required="true" />
89+
</ParameterGroup>
90+
<Task>
91+
<Using Namespace="System" />
92+
<Using Namespace="System.Collections.Generic" />
93+
<Using Namespace="System.IO" />
94+
<Using Namespace="System.Text" />
95+
<Using Namespace="System.Text.RegularExpressions" />
96+
<Code Type="Fragment" Language="cs"><![CDATA[
97+
// Reduce the static web asset endpoints to the minimal fingerprint mapping BlazorWebView needs:
98+
// the fingerprinted route and its logical, non-fingerprinted label. Only primary (non-compressed)
99+
// endpoints that actually carry a fingerprint are relevant; everything else serves directly.
100+
var byRoute = new SortedDictionary<string, string>(StringComparer.Ordinal);
101+
foreach (var endpoint in Endpoints)
102+
{
103+
var selectors = endpoint.GetMetadata("Selectors");
104+
if (!string.IsNullOrEmpty(selectors) && selectors != "[]")
105+
{
106+
// Content-negotiated alternative (gzip/brotli); not a distinct asset.
107+
continue;
108+
}
109+
110+
var properties = endpoint.GetMetadata("EndpointProperties") ?? string.Empty;
111+
if (!Regex.IsMatch(properties, "\"Name\"\\s*:\\s*\"fingerprint\""))
112+
{
113+
// Not a fingerprinted route (the plain route is served directly).
114+
continue;
115+
}
116+
117+
var labelMatch = Regex.Match(properties, "\"Name\"\\s*:\\s*\"label\"\\s*,\\s*\"Value\"\\s*:\\s*\"(?<v>(?:[^\"\\\\]|\\\\.)*)\"");
118+
if (!labelMatch.Success)
119+
{
120+
continue;
121+
}
122+
123+
var route = endpoint.ItemSpec;
124+
var label = labelMatch.Groups["v"].Value;
125+
if (!string.IsNullOrEmpty(route) && !string.IsNullOrEmpty(label))
126+
{
127+
byRoute[route] = label;
128+
}
129+
}
130+
131+
static string JsonEscape(string value) =>
132+
value.Replace("\\", "\\\\").Replace("\"", "\\\"");
133+
134+
var builder = new StringBuilder();
135+
builder.Append("{\"Assets\":[");
136+
var first = true;
137+
foreach (var pair in byRoute)
138+
{
139+
if (!first)
140+
{
141+
builder.Append(',');
142+
}
143+
first = false;
144+
builder.Append("{\"Route\":\"").Append(JsonEscape(pair.Key))
145+
.Append("\",\"Label\":\"").Append(JsonEscape(pair.Value)).Append("\"}");
146+
}
147+
builder.Append("]}");
148+
149+
var content = builder.ToString();
150+
Directory.CreateDirectory(Path.GetDirectoryName(OutputFile));
151+
152+
// Only write when the content changes so incremental builds stay clean.
153+
if (!File.Exists(OutputFile) || File.ReadAllText(OutputFile) != content)
154+
{
155+
File.WriteAllText(OutputFile, content);
156+
}
157+
]]></Code>
158+
</Task>
159+
</UsingTask>
160+
79161
<Target Name="_BundleMauiBlazorAssetManifest"
80162
AfterTargets="ConvertStaticWebAssetsToMauiAssets"
81-
Condition="'$(StaticWebAssetEndpointsBuildManifestPath)' != '' and Exists('$(StaticWebAssetEndpointsBuildManifestPath)')">
163+
DependsOnTargets="ResolveStaticWebAssetsConfiguration"
164+
Condition="'@(StaticWebAssetEndpoint)' != ''">
165+
<PropertyGroup>
166+
<_MauiBlazorAssetManifestFile>$(IntermediateOutputPath)maui\blazor-asset-manifest.json</_MauiBlazorAssetManifestFile>
167+
</PropertyGroup>
168+
<_GenerateMauiBlazorAssetManifest Endpoints="@(StaticWebAssetEndpoint)"
169+
OutputFile="$(_MauiBlazorAssetManifestFile)" />
82170
<ItemGroup>
83-
<MauiAsset Include="$(StaticWebAssetEndpointsBuildManifestPath)">
171+
<MauiAsset Include="$(_MauiBlazorAssetManifestFile)" Condition="Exists('$(_MauiBlazorAssetManifestFile)')">
84172
<Link>_maui/blazor-asset-manifest.json</Link>
85173
<TargetPath>_maui/blazor-asset-manifest.json</TargetPath>
86174
</MauiAsset>

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