Enable setting OkHttpClient for FirebaseFunctions

Author: svenjacobs

firebase-functions/src/androidTest/java/com/google/firebase/functions/FirebaseFunctionsTest.java

@@ -24,6 +24,8 @@
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
+import okhttp3.OkHttpClient;
+
 @RunWith(AndroidJUnit4.class)
 public class FirebaseFunctionsTest {
 
@@ -101,6 +103,17 @@ public void testEmulatorSettings() {
     assertEquals(functions1.getURL("foo").toString(), functions2.getURL("foo").toString());
   }
 
+  @Test
+  public void testSetOkHttpClient() {
+    OkHttpClient client = new OkHttpClient.Builder().build();
+    FirebaseApp app = getApp("testSetOkHttpClient");
+    FirebaseFunctions functions = FirebaseFunctions.getInstance(app);
+
+    functions.setOkHttpClient(client);
+
+    assertEquals(client, functions.getOkHttpClient());
+  }
+
   private FirebaseApp getApp(String name) {
     return FirebaseApp.initializeApp(
         InstrumentationRegistry.getInstrumentation().getTargetContext(),

firebase-functions/src/main/java/com/google/firebase/functions/FirebaseFunctions.java

@@ -63,7 +63,7 @@ public class FirebaseFunctions {
   private static boolean providerInstallStarted = false;
 
   // The network client to use for HTTPS requests.
-  private final OkHttpClient client;
+  private OkHttpClient client;
 
   // A serializer to encode/decode parameters and return values.
   private final Serializer serializer;
@@ -277,6 +277,19 @@ public void useEmulator(@NonNull String host, int port) {
     this.emulatorSettings = new EmulatedServiceSettings(host, port);
   }
 
+  /**
+   * Sets the OkHttpClient instance used by this FirebaseFunctions instance.
+   *
+   * @param client The OkHttpClient instance
+   */
+  public void setOkHttpClient(OkHttpClient client) {
+    this.client = client;
+  }
+
+  OkHttpClient getOkHttpClient() {
+    return this.client;
+  }
+
   /**
    * Calls a Callable HTTPS trigger endpoint.
    *