Fix: Allow OCI archives without manifest annotations (#397)

Fixes #369

Per the OCI Image Spec, manifest descriptor annotations are optional.
Previously, archives without annotations would fail to import with
"Failed to import image".

**Changes:**
- Modified `getImageReferencefromDescriptor` to return digest-based
references (`untagged@sha256:...`) when annotations are missing
- Removed guard that skipped manifests without annotations
- Added test case with `scratch_no_annotations.tar`

**Testing:**
All 167 tests pass, including new test for images without annotations.

Package.swift

@@ -90,7 +90,10 @@ let package = Package(
             name: "ContainerizationUnitTests",
             dependencies: ["Containerization"],
             path: "Tests/ContainerizationTests",
-            resources: [.copy("ImageTests/Resources/scratch.tar")]
+            resources: [
+                .copy("ImageTests/Resources/scratch.tar"),
+                .copy("ImageTests/Resources/scratch_no_annotations.tar"),
+            ]
         ),
         .target(
             name: "ContainerizationEXT4",

Sources/Containerization/Image/ImageStore/ImageStore+OCILayout.swift

@@ -80,9 +80,7 @@ extension ImageStore {
         let (id, tempDir) = try await self.contentStore.newIngestSession()
         do {
             for descriptor in index.manifests {
-                guard let reference = client.getImageReferencefromDescriptor(descriptor: descriptor) else {
-                    continue
-                }
+                let reference = client.getImageReferencefromDescriptor(descriptor: descriptor)
                 let ref = try Reference.parse(reference)
                 let name = ref.path
                 let operation = ImportOperation(name: name, contentStore: self.contentStore, client: client, ingestDir: tempDir, progress: progress)

Sources/ContainerizationOCI/Client/LocalOCILayoutClient.swift

@@ -205,11 +205,8 @@ extension LocalOCILayoutClient {
         descriptor.annotations = annotations
     }
 
-    package func getImageReferencefromDescriptor(descriptor: Descriptor) -> String? {
+    package func getImageReferencefromDescriptor(descriptor: Descriptor) -> String {
         let annotations = descriptor.annotations
-        guard let annotations else {
-            return nil
-        }
 
         // Annotations here do not conform to the OCI image specification.
         // The interpretation of the annotations "org.opencontainers.image.ref.name" and
@@ -220,16 +217,21 @@ extension LocalOCILayoutClient {
         //     https://github.com/moby/buildkit/issues/4615#issuecomment-2521810830
         // Until a consensus is reached, the preference is given to "com.apple.containerization.image.name" and then to
         // using "io.containerd.image.name" as it is the next safest choice
-        if let name = annotations[AnnotationKeys.containerizationImageName] {
-            return name
+        if let annotations {
+            if let name = annotations[AnnotationKeys.containerizationImageName] {
+                return name
+            }
+            if let name = annotations[AnnotationKeys.containerdImageName] {
+                return name
+            }
+            if let name = annotations[AnnotationKeys.openContainersImageName] {
+                return name
+            }
         }
-        if let name = annotations[AnnotationKeys.containerdImageName] {
-            return name
-        }
-        if let name = annotations[AnnotationKeys.openContainersImageName] {
-            return name
-        }
-        return nil
+
+        // Fallback: Generate digest-based reference for images without annotations
+        // This makes sure OCI spec compliance as annotations are optional
+        return "untagged@\(descriptor.digest)"
     }
 
     package enum Error: Swift.Error {

Tests/ContainerizationTests/ImageTests/ImageStoreTests.swift

@@ -87,4 +87,26 @@ public class ImageStoreTests: ContainsAuth {
         let _ = try await self.store.tag(existing: imageReference, new: upstreamTag)
         try await self.store.push(reference: upstreamTag, auth: authentication)
     }
+
+    @Test func testLoadImageWithoutAnnotations() async throws {
+        let fileManager = FileManager.default
+        let tempDir = fileManager.uniqueTemporaryDirectory()
+        defer {
+            try? fileManager.removeItem(at: tempDir)
+        }
+
+        let tarPath = Foundation.Bundle.module.url(forResource: "scratch_no_annotations", withExtension: "tar")!
+        let reader = try ArchiveReader(format: .pax, filter: .none, file: tarPath)
+        try reader.extractContents(to: tempDir)
+
+        let loaded = try await self.store.load(from: tempDir)
+
+        #expect(loaded.count == 1)
+
+        let reference = loaded.first!.reference
+        #expect(reference.hasPrefix("untagged@sha256:"))
+
+        let retrieved = try await self.store.get(reference: reference)
+        #expect(retrieved.reference == reference)
+    }
 }