fix: HttpClient.Factory instances can be prioritized

Introduce a scoring system so that HttpClient.Factory instances
provided by the SPI can be prioritized.
The higher the priority, the higher the chances
that the factory instance will be selected automatically
to create HttpClient instances.

Signed-off-by: GitHub <bot@example.com>

kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/http/HttpClient.java

@@ -58,6 +58,15 @@ default boolean isDefault() {
       return false;
     }
 
+    /**
+     * The priority of the implementation. The higher the priority the more likely it will be used.
+     * 
+     * @return the priority.
+     */
+    default int priority() {
+      return 0;
+    }
+
   }
 
   interface DerivedClientBuilder {

kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/utils/HttpClientUtils.java

@@ -166,7 +166,8 @@ private static HttpClient.Factory getFactory(ServiceLoader<HttpClient.Factory> l
             + "choosing the first non-default implementation. "
             + "You should exclude dependencies that aren't needed or use an explicit association of the HttpClient.Factory.");
       }
-      if (factory == null || (factory.isDefault() && !possible.isDefault())) {
+      if (factory == null || (factory.isDefault() && !possible.isDefault())
+          || (!factory.isDefault()) && factory.priority() < possible.priority()) {
         factory = possible;
       }
     }

kubernetes-client-api/src/test/java/io/fabric8/kubernetes/client/utils/HttpClientUtilsTest.java

@@ -17,7 +17,10 @@
 
 import io.fabric8.kubernetes.client.Config;
 import io.fabric8.kubernetes.client.ConfigBuilder;
+import io.fabric8.kubernetes.client.KubernetesClientException;
+import io.fabric8.kubernetes.client.http.HttpClient;
 import io.fabric8.kubernetes.client.http.Interceptor;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
@@ -27,17 +30,28 @@
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.mockito.MockedStatic;
 
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.List;
+import java.util.ServiceLoader;
 import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.AssertionsForClassTypes.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
 
 class HttpClientUtilsTest {
 
@@ -182,4 +196,100 @@ void withNoHttpProxyProvidedReturnsNull() throws MalformedURLException {
       assertThat(url).isNull();
     }
   }
+
+  @Nested
+  @DisplayName("getHttpClientFactory")
+  class GetHttpClientFactory {
+
+    private List<HttpClient.Factory> factories;
+    @SuppressWarnings("rawtypes")
+    private MockedStatic<ServiceLoader> mockedStaticServiceLoader;
+
+    @BeforeEach
+    void setUp() {
+      // n.b. Since ServiceLoader is mocked for this test, it's not possible to use AssertJ assertions.
+      factories = new ArrayList<>();
+      mockedStaticServiceLoader = mockStatic(ServiceLoader.class);
+      @SuppressWarnings("unchecked")
+      final ServiceLoader<HttpClient.Factory> mockServiceLoader = mock(ServiceLoader.class);
+      when(mockServiceLoader.iterator()).thenAnswer(i -> new ArrayList<>(factories).iterator());
+      when(ServiceLoader.load(eq(HttpClient.Factory.class), any())).thenReturn(mockServiceLoader);
+      mockedStaticServiceLoader.when(() -> ServiceLoader.load(eq(HttpClient.Factory.class)))
+          .thenReturn(mockServiceLoader);
+    }
+
+    @AfterEach
+    void tearDown() {
+      factories.clear();
+      mockedStaticServiceLoader.close();
+    }
+
+    @Test
+    @DisplayName("With no implementations, should throw exception")
+    void withNoImplementations() {
+      final KubernetesClientException result = assertThrows(KubernetesClientException.class,
+          HttpClientUtils::getHttpClientFactory);
+      assertEquals(
+          "No httpclient implementations found on the context classloader, please ensure your classpath includes an implementation jar",
+          result.getMessage());
+    }
+
+    @Test
+    @DisplayName("With default implementation, should return default")
+    void withDefault() {
+      factories.add(new DefaultHttpClientFactory());
+      assertEquals(DefaultHttpClientFactory.class, HttpClientUtils.getHttpClientFactory().getClass());
+    }
+
+    @Test
+    @DisplayName("With default and other implementation, should return other")
+    void withDefaultAndOther() {
+      factories.add(new OtherHttpClientFactory());
+      factories.add(new DefaultHttpClientFactory());
+      assertEquals(OtherHttpClientFactory.class, HttpClientUtils.getHttpClientFactory().getClass());
+    }
+
+    @Test
+    @DisplayName("With default and other implementation, should return Priority")
+    void withDefaultAndPriorityAndOther() {
+      factories.add(new OtherHttpClientFactory());
+      factories.add(new PriorityHttpClientFactory());
+      factories.add(new DefaultHttpClientFactory());
+      assertEquals(PriorityHttpClientFactory.class, HttpClientUtils.getHttpClientFactory().getClass());
+    }
+
+    private final class DefaultHttpClientFactory implements HttpClient.Factory {
+
+      @Override
+      public HttpClient.Builder newBuilder() {
+        return null;
+      }
+
+      @Override
+      public boolean isDefault() {
+        return true;
+      }
+    }
+
+    private final class OtherHttpClientFactory implements HttpClient.Factory {
+
+      @Override
+      public HttpClient.Builder newBuilder() {
+        return null;
+      }
+    }
+
+    private final class PriorityHttpClientFactory implements HttpClient.Factory {
+
+      @Override
+      public HttpClient.Builder newBuilder() {
+        return null;
+      }
+
+      @Override
+      public int priority() {
+        return Integer.MAX_VALUE;
+      }
+    }
+  }
 }