Skip stub inner packages when parsing bundle manifests

Real-world bundles like Microsoft.DesktopAppInstaller include 'stub'
inner packages whose FileName attribute is e.g.
'AppxMetadata\Stub\AppInstaller_x64_stub.msix'. These are metadata-only
placeholders used by the platform for delta servicing — they don't carry
a real block map. Diffing them threw 'Bundle does not contain expected
inner package'.

- BundleManifestParser now normalizes backslash separators and skips
  entries under AppxMetadata/.
- New test BundleManifestParser_SkipsStubPackages.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: aclinick

MSIXplainer.Core.Tests/UpdateDiffBundleTests.cs

@@ -353,4 +353,29 @@ [new SyntheticFile("App.exe", Bytes("a", 100))]),
             File.Delete(newBundle);
         }
     }
+
+    [Fact]
+    public void BundleManifestParser_SkipsStubPackages()
+    {
+        // Real DesktopAppInstaller bundles include stub packages whose FileName
+        // attribute is "AppxMetadata\Stub\AppInstaller_x64_stub.msix". These are
+        // metadata-only placeholders (no real payload), so the parser must skip
+        // them — otherwise UpdateDiffService later tries to read their block map
+        // and fails with "Bundle does not contain expected inner package".
+        var xml = $$"""
+            <?xml version="1.0" encoding="utf-8"?>
+            <Bundle xmlns="{{BundleNs.NamespaceName}}">
+              <Identity Name="Test.App" Publisher="CN=Test" Version="1.0.0.0" />
+              <Packages>
+                <Package Type="application" Version="1.0.0.0" Architecture="x64" FileName="App_x64.msix" Size="100" Offset="0" />
+                <Package Type="application" Version="1.0.0.0" Architecture="x64" FileName="AppxMetadata\Stub\App_x64_stub.msix" Size="50" Offset="0" />
+              </Packages>
+            </Bundle>
+            """;
+
+        var inners = BundleManifestParser.Parse(xml);
+
+        Assert.Single(inners);
+        Assert.Equal("App_x64.msix", inners[0].FileName);
+    }
 }

MSIXplainer.Core/Services/BundleManifestParser.cs

@@ -62,6 +62,16 @@ public static IReadOnlyList<BundleInnerPackage> Parse(string xml)
             var fileName = p.Attribute("FileName")?.Value ?? string.Empty;
             if (string.IsNullOrEmpty(fileName)) continue;
 
+            // Normalize path separator: bundle manifests sometimes use '\' but
+            // the underlying ZIP entry names always use '/'.
+            fileName = fileName.Replace('\\', '/');
+
+            // Skip stub packages (AppxMetadata/Stub/*.msix). Stubs are metadata-only
+            // placeholders used by the platform for bundle delta servicing — they
+            // don't carry a real block map or payload, so they have nothing to diff.
+            if (fileName.StartsWith("AppxMetadata/", StringComparison.OrdinalIgnoreCase))
+                continue;
+
             var type = p.Attribute("Type")?.Value ?? "application";
             var version = p.Attribute("Version")?.Value ?? string.Empty;
             var arch = p.Attribute("Architecture")?.Value ?? "neutral";

MSIXplainer/Package.appxmanifest

@@ -11,7 +11,7 @@
   <Identity
     Name="Clinick.msixplainer"
     Publisher="CN=46604BD4-AFD9-4B23-8EB3-10EAF66872A5"
-    Version="1.0.23.0" />
+    Version="1.0.24.0" />
 
   <mp:PhoneIdentity PhoneProductId="3a09e9f9-55b1-418a-9e63-9a662f1a29bc" PhonePublisherId="00000000-0000-0000-0000-000000000000"/>