Add missing nullability annotations to Functions. (#601)

Author: vkryachko

firebase-functions/firebase-functions.gradle

@@ -19,7 +19,6 @@ plugins {
 firebaseLibrary {
     testLab.enabled = true
     publishSources = true
-    staticAnalysis.disableKotlinInteropLint()
 }
 
 android {

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

@@ -128,7 +128,8 @@ public void onProviderInstallFailed(int i, android.content.Intent intent) {
    * @param app The app for the Firebase project.
    * @param region The region for the HTTPS trigger, such as "us-central1".
    */
-  public static FirebaseFunctions getInstance(FirebaseApp app, String region) {
+  @NonNull
+  public static FirebaseFunctions getInstance(@NonNull FirebaseApp app, @NonNull String region) {
     Preconditions.checkNotNull(app, "You must call FirebaseApp.initializeApp first.");
     Preconditions.checkNotNull(region);
 
@@ -143,7 +144,8 @@ public static FirebaseFunctions getInstance(FirebaseApp app, String region) {
    *
    * @param app The app for the Firebase project.
    */
-  public static FirebaseFunctions getInstance(FirebaseApp app) {
+  @NonNull
+  public static FirebaseFunctions getInstance(@NonNull FirebaseApp app) {
     return getInstance(app, "us-central1");
   }
 
@@ -152,17 +154,20 @@ public static FirebaseFunctions getInstance(FirebaseApp app) {
    *
    * @param region The region for the HTTPS trigger, such as "us-central1".
    */
-  public static FirebaseFunctions getInstance(String region) {
+  @NonNull
+  public static FirebaseFunctions getInstance(@NonNull String region) {
     return getInstance(FirebaseApp.getInstance(), region);
   }
 
   /** Creates a Cloud Functions client with the default app. */
+  @NonNull
   public static FirebaseFunctions getInstance() {
     return getInstance(FirebaseApp.getInstance(), "us-central1");
   }
 
   /** Returns a reference to the Callable HTTPS trigger with the given name. */
-  public HttpsCallableReference getHttpsCallable(String name) {
+  @NonNull
+  public HttpsCallableReference getHttpsCallable(@NonNull String name) {
     return new HttpsCallableReference(this, name);
   }
 

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

@@ -76,6 +76,7 @@ public class HttpsCallableReference {
    * @see java.io.IOException
    * @see FirebaseFunctionsException
    */
+  @NonNull
   public Task<HttpsCallableResult> call(@Nullable Object data) {
     return functionsClient.call(name, data, options);
   }
@@ -94,6 +95,7 @@ public Task<HttpsCallableResult> call(@Nullable Object data) {
    *
    * @return A Task that will be completed when the HTTPS request has completed.
    */
+  @NonNull
   public Task<HttpsCallableResult> call() {
     return functionsClient.call(name, null, options);
   }
@@ -104,11 +106,10 @@ public Task<HttpsCallableResult> call() {
    * @param timeout The length of the timeout, in the given units.
    * @param units The units for the specified timeout.
    */
-  public void setTimeout(long timeout, TimeUnit units) {
+  public void setTimeout(long timeout, @NonNull TimeUnit units) {
     options.setTimeout(timeout, units);
   }
 
-  @NonNull
   /**
    * Returns the timeout for calls from this instance of Functions.
    *
@@ -124,7 +125,8 @@ public long getTimeout() {
    * @param timeout The length of the timeout, in the given units.
    * @param units The units for the specified timeout.
    */
-  public HttpsCallableReference withTimeout(long timeout, TimeUnit units) {
+  @NonNull
+  public HttpsCallableReference withTimeout(long timeout, @NonNull TimeUnit units) {
     HttpsCallableReference other = new HttpsCallableReference(functionsClient, name);
     other.setTimeout(timeout, units);
     return other;

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

@@ -14,6 +14,8 @@
 
 package com.google.firebase.functions;
 
+import androidx.annotation.Nullable;
+
 /** The result of calling a HttpsCallableReference function. */
 public class HttpsCallableResult {
   // The actual result data, as generic types decoded from JSON.
@@ -30,6 +32,7 @@ public class HttpsCallableResult {
    * array, this object would be a List<Object>. If your trigger returned a JavaScript object with
    * keys and values, this object would be a Map<String, Object>.
    */
+  @Nullable
   public Object getData() {
     return data;
   }