Issue f2prateek#141: Emit defaultValue if underlying onSharedPreferen…

…ceChangedListener returns null

gradle.properties

@@ -1,5 +1,5 @@
 GROUP=com.f2prateek.rx.preferences2
-VERSION_NAME=2.0.2-SNAPSHOT
+VERSION_NAME=issue~141-SNAPSHOT
 
 POM_DESCRIPTION=Reactive SharedPreferences for Android
 

rx-preferences/src/main/java/com/f2prateek/rx/preferences2/RealPreference.java

@@ -35,8 +35,8 @@ interface Adapter<T> {
   private final Adapter<T> adapter;
   private final Observable<T> values;
 
-  RealPreference(SharedPreferences preferences, final String key, T defaultValue,
-      Adapter<T> adapter, Observable<String> keyChanges) {
+  RealPreference(SharedPreferences preferences, final String key, final T defaultValue,
+                 Adapter<T> adapter, Observable<String> keyChanges) {
     this.preferences = preferences;
     this.key = key;
     this.defaultValue = defaultValue;
@@ -50,7 +50,11 @@ interface Adapter<T> {
         .startWith("<init>") // Dummy value to trigger initial load.
         .map(new Function<String, T>() {
           @Override public T apply(String s) {
-            return get();
+            if(s.equals(RxSharedPreferences.NULL_KEY_EMISSION)) {
+              return defaultValue;
+            } else {
+              return get();
+            }
           }
         });
   }

rx-preferences/src/main/java/com/f2prateek/rx/preferences2/RxSharedPreferences.java

@@ -26,6 +26,8 @@ public final class RxSharedPreferences {
   private static final Long DEFAULT_LONG = 0L;
   private static final String DEFAULT_STRING = "";
 
+  static final String NULL_KEY_EMISSION = "null_key_emission";
+
   /** Create an instance of {@link RxSharedPreferences} for {@code preferences}. */
   @CheckResult @NonNull
   public static RxSharedPreferences create(@NonNull SharedPreferences preferences) {
@@ -43,7 +45,11 @@ private RxSharedPreferences(final SharedPreferences preferences) {
         final OnSharedPreferenceChangeListener listener = new OnSharedPreferenceChangeListener() {
           @Override
           public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
-            emitter.onNext(key);
+            if(key == null) {
+              emitter.onNext(NULL_KEY_EMISSION);
+            } else {
+              emitter.onNext(key);
+            }
           }
         };
 

rx-preferences/src/test/java/com/f2prateek/rx/preferences2/PreferenceTest.java

@@ -10,6 +10,7 @@
 import java.util.List;
 import java.util.Set;
 import org.junit.Before;
+import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -266,6 +267,21 @@ public class PreferenceTest {
     observer.assertValue("bar");
   }
 
+  @Ignore("Robolectric needs to be updated to support API 30")
+  @Test public void asObservableWhenBackingPrefsCleared() {
+    Preference<String> preference = rxPreferences.getString("foo", "bar");
+
+    RecordingObserver<String> observer = observerRule.create();
+    preference.asObservable().subscribe(observer);
+    observer.assertValue("bar");
+
+    preferences.edit().putString("foo", "baz").commit();
+    observer.assertValue("baz");
+
+    preferences.edit().clear().commit();
+    observer.assertValue("bar");
+  }
+
   @Test public void asConsumer() throws Exception {
     Preference<String> preference = rxPreferences.getString("foo");
     Consumer<? super String> consumer = preference.asConsumer();