Support downloading plugins using ORAS

modules/nf-commons/build.gradle

@@ -35,6 +35,7 @@ dependencies {
     api 'dev.failsafe:failsafe:3.1.0'
     // patch gson dependency required by pf4j
     api 'com.google.code.gson:gson:2.10.1'
+    implementation 'land.oras:oras-java-sdk:0.2.4'
 
     /* testImplementation inherited from top gradle build file */
     testImplementation(testFixtures(project(":nextflow")))

modules/nf-commons/src/main/nextflow/plugin/OrasPluginDownloader.groovy

@@ -0,0 +1,66 @@
+package nextflow.plugin
+
+import groovy.transform.CompileStatic
+import land.oras.ContainerRef
+import land.oras.Manifest
+import land.oras.Registry
+import org.pf4j.PluginRuntimeException
+
+import java.nio.file.Files
+import java.nio.file.Path
+
+/**
+ * Support downloading plugins from an ORAS (OCI Registry As Storage)
+ * location.
+ *
+ * NOTE: logically this should implement pf4j's FileDownloader interface,
+ * but unfortunately that interface uses java.net.URL which doesn't support
+ * custom URI protocols.
+ *
+ * See https://oras.land/
+ */
+@CompileStatic
+class OrasPluginDownloader {
+    private static final String PROTOCOL = "oras://"
+    private static final String ARTIFACT_TYPE = "application/vnd.nextflow.plugin+zip"
+
+    static boolean canDownload(String uri) {
+        return uri.startsWith(PROTOCOL)
+    }
+
+    Path downloadFile(String uri) throws IOException {
+        if (!canDownload(uri)) {
+            throw new PluginRuntimeException("URI protocol not supported by ORAS downloader: {}", uri);
+        }
+        return downloadOras(uri)
+    }
+
+    private static Path downloadOras(String uri) {
+        Path destination = Files.createTempDirectory("oras-update-downloader")
+        destination.toFile().deleteOnExit()
+
+        // strip the oras:// prefix since it's just a marker
+        ContainerRef source = ContainerRef.parse(uri.replaceFirst("oras://", ""))
+        Registry registry = Registry.Builder.builder()
+            // use http on localhost, require https everywhere else
+            .withInsecure(source.registry.startsWith("localhost:"))
+            .build()
+
+        // grab oras metadata about the url
+        Manifest manifest = registry.getManifest(source)
+        String type = manifest.getArtifactType()
+        if (type != ARTIFACT_TYPE) {
+            throw new PluginRuntimeException("Not a nextflow plugin: {}", uri)
+        }
+        // get the filename of the plugin artifact, which should be in layer 0
+        def layers = manifest.getLayers()
+        if (layers.size() < 1) {
+            throw new PluginRuntimeException("Unable to find nextflow plugin at: {}", uri)
+        }
+        String filename = layers[0].annotations['org.opencontainers.image.title']
+
+        // download the plugin artifact
+        registry.pullArtifact(source, destination, true)
+        return destination.resolve(filename)
+    }
+}

modules/nf-commons/src/main/nextflow/plugin/PluginUpdater.groovy

@@ -17,6 +17,8 @@
 
 package nextflow.plugin
 
+import org.pf4j.update.FileVerifier
+
 import static java.nio.file.StandardCopyOption.*
 
 import java.nio.file.Files
@@ -244,6 +246,27 @@ class PluginUpdater extends UpdateManager {
         return Failsafe.with(policy).get(supplier)
     }
 
+    // override this method from the parent class to support oras:// downloads
+    @Override
+    protected Path downloadPlugin(String id, String version) {
+        try {
+            def release = findReleaseForPlugin(id, version)
+
+            // pf4j's FileDownloader interface uses java.net.URL, which
+            // doesn't support custom protocols. This means we can't use
+            // it for oras:// URIs and instead have to call the ORAS downloader
+            // directly in such cases
+            Path downloaded = OrasPluginDownloader.canDownload(release.url)
+                ? new OrasPluginDownloader().downloadFile(release.url)
+                : getFileDownloader(id).downloadFile(new URL(release.url))
+
+            getFileVerifier(id).verify(new FileVerifier.Context(id, release), downloaded);
+            return downloaded;
+        } catch (IOException e) {
+            throw new PluginRuntimeException(e, "Error during download of plugin {}", id);
+        }
+    }
+
     protected <T> RetryPolicy<T> retryPolicy(String id, String version) {
         final listener = new dev.failsafe.event.EventListener<ExecutionAttemptedEvent<T>>() {
             @Override