registry: fix provider discovery (#320)

Author: roseyang62

registry/registry-client/src/main/java/com/salesforce/multicloudj/registry/driver/AbstractRegistry.java

@@ -37,10 +37,6 @@ protected AbstractRegistry(Builder<?, ?> builder) {
         this.proxyEndpoint = builder.getProxyEndpoint();
         this.credentialsOverrider = builder.getCredentialsOverrider();
         this.targetPlatform = builder.getPlatform() != null ? builder.getPlatform() : Platform.DEFAULT;
-
-        if (StringUtils.isBlank(registryEndpoint)) {
-            throw new InvalidArgumentException("Registry endpoint is required");
-        }
     }
 
     @Override

registry/registry-client/src/test/java/com/salesforce/multicloudj/registry/driver/AbstractRegistryTest.java

@@ -330,6 +330,9 @@ public TestBuilder self() {
 
             @Override
             public TestRegistry build() {
+                if (registryEndpoint == null || registryEndpoint.isBlank()) {
+                    throw new InvalidArgumentException("Registry endpoint is required");
+                }
                 return new TestRegistry(this);
             }
         }

registry/registry-gcp/src/main/java/com/salesforce/multicloudj/registry/gcp/GcpRegistry.java

@@ -9,6 +9,7 @@
 import com.salesforce.multicloudj.common.exceptions.SubstrateSdkException;
 import com.salesforce.multicloudj.common.exceptions.UnknownException;
 import com.salesforce.multicloudj.common.gcp.CommonErrorCodeMapping;
+import com.salesforce.multicloudj.common.gcp.GcpConstants;
 import com.salesforce.multicloudj.common.gcp.GcpCredentialsProvider;
 import com.salesforce.multicloudj.registry.driver.AbstractRegistry;
 import com.salesforce.multicloudj.registry.driver.OciRegistryClient;
@@ -29,7 +30,6 @@
 @AutoService(AbstractRegistry.class)
 public class GcpRegistry extends AbstractRegistry {
 
-    public static final String PROVIDER_ID = "gcp";
     private static final String GCP_AUTH_USERNAME = "oauth2accesstoken";
     private static final String CLOUD_PLATFORM_SCOPE = "https://www.googleapis.com/auth/cloud-platform";
 
@@ -41,9 +41,13 @@ public class GcpRegistry extends AbstractRegistry {
     /** Lazily initialized credentials with double-checked locking. */
     private volatile GoogleCredentials credentials;
 
+    public GcpRegistry() {
+        this(new Builder());
+    }
+
     public GcpRegistry(Builder builder) {
         super(builder);
-        this.ociClient = new OciRegistryClient(registryEndpoint, this);
+        this.ociClient = registryEndpoint != null ? new OciRegistryClient(registryEndpoint, this) : null;
     }
 
     @Override
@@ -140,7 +144,11 @@ public void close() throws Exception {
         }
     }
 
-    public static final class Builder extends AbstractRegistry.Builder<GcpRegistry, Builder> {
+    public static class Builder extends AbstractRegistry.Builder<GcpRegistry, Builder> {
+
+        public Builder() {
+            providerId(GcpConstants.PROVIDER_ID);
+        }
 
         @Override
         public Builder self() {
@@ -149,8 +157,6 @@ public Builder self() {
 
         @Override
         public GcpRegistry build() {
-            providerId(PROVIDER_ID);
-            
             if (StringUtils.isBlank(registryEndpoint)) {
                 throw new InvalidArgumentException("Registry endpoint is required for GCP Artifact Registry");
             }

registry/registry-gcp/src/test/java/com/salesforce/multicloudj/registry/gcp/GcpRegistryTest.java

@@ -63,6 +63,13 @@ void testBuilderAndBasicProperties() throws Exception {
         });
     }
 
+    @Test
+    void testNoArgConstructor_ForServiceLoaderDiscovery() {
+        GcpRegistry registry = new GcpRegistry();
+        assertEquals("gcp", registry.getProviderId());
+        assertNotNull(registry.builder());
+    }
+
     @Test
     void testGetAuthToken_Success() throws Exception {
         try (MockedStatic<GoogleCredentials> mockedStatic = mockStatic(GoogleCredentials.class)) {