Allow users to set a specific ContainerImageFormat to force OCI support

src/Containers/Microsoft.NET.Build.Containers/ContainerBuilder.cs

@@ -6,6 +6,12 @@
 
 namespace Microsoft.NET.Build.Containers;
 
+internal enum KnownImageFormats
+{
+    OCI,
+    Docker
+}
+
 internal static class ContainerBuilder
 {
     internal static async Task<int> ContainerizeAsync(
@@ -34,6 +40,7 @@ internal static async Task<int> ContainerizeAsync(
         string? archiveOutputPath,
         bool generateLabels,
         bool generateDigestLabel,
+        KnownImageFormats? imageFormat,
         ILoggerFactory loggerFactory,
         CancellationToken cancellationToken)
     {
@@ -99,6 +106,15 @@ internal static async Task<int> ContainerizeAsync(
         logger.LogInformation(Strings.ContainerBuilder_StartBuildingImage, imageName, string.Join(",", imageName), sourceImageReference);
         cancellationToken.ThrowIfCancellationRequested();
 
+        // forcibly change the media type if required
+        imageBuilder.ManifestMediaType = imageFormat switch
+        {
+            null => imageBuilder.ManifestMediaType,
+            KnownImageFormats.Docker => SchemaTypes.DockerManifestV2,
+            KnownImageFormats.OCI => SchemaTypes.OciManifestV1,
+            _ => imageBuilder.ManifestMediaType // should be impossible unless we add to the enum
+        };
+
         Layer newLayer = Layer.FromDirectory(publishDirectory.FullName, workingDir, imageBuilder.IsWindows, imageBuilder.ManifestMediaType);
         imageBuilder.AddLayer(newLayer);
         imageBuilder.SetWorkingDirectory(workingDir);

src/Containers/Microsoft.NET.Build.Containers/ImageBuilder.cs

@@ -19,7 +19,6 @@ internal sealed class ImageBuilder
 
     // the mutable internal manifest that we're building by modifying the base and applying customizations
     private readonly ManifestV2 _manifest;
-    private readonly string _manifestMediaType;
     private readonly ImageConfig _baseImageConfig;
     private readonly ILogger _logger;
 
@@ -32,15 +31,15 @@ internal sealed class ImageBuilder
     public ImageConfig BaseImageConfig => _baseImageConfig;
 
     /// <summary>
-    /// MediaType of the output manifest.
+    /// MediaType of the output manifest. By default, this will be the same as the base image manifest.
     /// </summary>
-    public string ManifestMediaType => _manifestMediaType; // output the same media type as the base image manifest.
+    public string ManifestMediaType { get; set; }
 
     internal ImageBuilder(ManifestV2 manifest, string manifestMediaType, ImageConfig baseImageConfig, ILogger logger)
     {
         _baseImageManifest = manifest;
         _manifest = new ManifestV2() { SchemaVersion = manifest.SchemaVersion, Config = manifest.Config, Layers = new(manifest.Layers), MediaType = manifest.MediaType };
-        _manifestMediaType = manifestMediaType;
+        ManifestMediaType = manifestMediaType;
         _baseImageConfig = baseImageConfig;
         _logger = logger;
     }
@@ -70,14 +69,20 @@ internal BuiltImage Build()
         ManifestConfig newManifestConfig = _manifest.Config with
         {
             digest = imageDigest,
-            size = imageSize
+            size = imageSize,
+            mediaType = ManifestMediaType switch
+            {
+                SchemaTypes.OciManifestV1 => SchemaTypes.OciImageConfigV1,
+                SchemaTypes.DockerManifestV2 => SchemaTypes.DockerContainerV1,
+                _ => SchemaTypes.OciImageConfigV1 // opinion - defaulting to modern here, but really this should never happen
+            }
         };
 
         ManifestV2 newManifest = new ManifestV2()
         {
             Config = newManifestConfig,
             SchemaVersion = _manifest.SchemaVersion,
-            MediaType = _manifest.MediaType,
+            MediaType = ManifestMediaType,
             Layers = _manifest.Layers
         };
 

src/Containers/Microsoft.NET.Build.Containers/PublicAPI/net10.0/PublicAPI.Unshipped.txt

@@ -243,6 +243,8 @@ Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateDigestLabel.get -> b
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateDigestLabel.set -> void
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GeneratedContainerNames.get -> Microsoft.Build.Framework.ITaskItem![]!
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GeneratedContainerNames.set -> void
+Microsoft.NET.Build.Containers.Tasks.CreateNewImage.ImageFormat.get -> string?
+Microsoft.NET.Build.Containers.Tasks.CreateNewImage.ImageFormat.set -> void
 Microsoft.NET.Build.Containers.Tasks.ParseContainerProperties
 Microsoft.NET.Build.Containers.Tasks.ParseContainerProperties.ContainerEnvironmentVariables.get -> Microsoft.Build.Framework.ITaskItem![]!
 Microsoft.NET.Build.Containers.Tasks.ParseContainerProperties.ContainerEnvironmentVariables.set -> void

src/Containers/Microsoft.NET.Build.Containers/PublicAPI/net472/PublicAPI.Unshipped.txt

@@ -90,6 +90,8 @@ Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateDigestLabel.get -> b
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateDigestLabel.set -> void
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GeneratedContainerNames.get -> Microsoft.Build.Framework.ITaskItem![]!
 Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GeneratedContainerNames.set -> void
+Microsoft.NET.Build.Containers.Tasks.CreateNewImage.ImageFormat.get -> string?
+Microsoft.NET.Build.Containers.Tasks.CreateNewImage.ImageFormat.set -> void
 override Microsoft.NET.Build.Containers.Tasks.CreateNewImage.ToolName.get -> string!
 override Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateCommandLineCommands() -> string!
 override Microsoft.NET.Build.Containers.Tasks.CreateNewImage.GenerateFullPathToTool() -> string!

src/Containers/Microsoft.NET.Build.Containers/Registry/SchemaTypes.cs

@@ -9,8 +9,11 @@ internal class SchemaTypes
     internal const string DockerContainerV1 = "application/vnd.docker.container.image.v1+json";
     internal const string DockerManifestListV2 = "application/vnd.docker.distribution.manifest.list.v2+json";
     internal const string DockerManifestV2 = "application/vnd.docker.distribution.manifest.v2+json";
+
     internal const string OciManifestV1 = "application/vnd.oci.image.manifest.v1+json"; // https://containers.gitbook.io/build-containers-the-hard-way/#registry-format-oci-image-manifest
     internal const string OciImageIndexV1 = "application/vnd.oci.image.index.v1+json";
+    internal const string OciImageConfigV1 = "application/vnd.oci.image.config.v1+json";
+
     internal const string DockerLayerGzip = "application/vnd.docker.image.rootfs.diff.tar.gzip";
     internal const string OciLayerGzipV1 = "application/vnd.oci.image.layer.v1.tar+gzip";
 }