2.x: Check runnable == null in *Scheduler.schedule*(). (#5748)

* 2.x: Check runnable == null in *Scheduler.schedule*().

* "run is null".

* sudo "run is null".

Author: artem-zinnatullin

src/main/java/io/reactivex/plugins/RxJavaPlugins.java

@@ -446,6 +446,8 @@ public static Scheduler onNewThreadScheduler(@NonNull Scheduler defaultScheduler
      */
     @NonNull
     public static Runnable onSchedule(@NonNull Runnable run) {
+        ObjectHelper.requireNonNull(run, "run is null");
+
         Function<? super Runnable, ? extends Runnable> f = onScheduleHandler;
         if (f == null) {
             return run;

src/test/java/io/reactivex/plugins/RxJavaPluginsTest.java

@@ -1369,8 +1369,6 @@ public void subscribeActual(CompletableObserver t) {
 
             assertNull(RxJavaPlugins.onAssembly((Maybe)null));
 
-            assertNull(RxJavaPlugins.onSchedule(null));
-
             Maybe myb = new Maybe() {
                 @Override
                 public void subscribeActual(MaybeObserver t) {
@@ -1381,10 +1379,7 @@ public void subscribeActual(MaybeObserver t) {
             assertSame(myb, RxJavaPlugins.onAssembly(myb));
 
 
-            assertNull(RxJavaPlugins.onSchedule(null));
-
             Runnable action = Functions.EMPTY_RUNNABLE;
-
             assertSame(action, RxJavaPlugins.onSchedule(action));
 
             class AllSubscriber implements Subscriber, Observer, SingleObserver, CompletableObserver, MaybeObserver {

src/test/java/io/reactivex/schedulers/AbstractSchedulerTests.java

@@ -742,4 +742,34 @@ public void run() {
         assertSame(countDownRunnable, wrapper.getWrappedRunnable());
         disposable.dispose();
     }
-}
+
+    @Test
+    public void scheduleDirectNullRunnable() {
+        try {
+            getScheduler().scheduleDirect(null);
+            fail();
+        } catch (NullPointerException npe) {
+            assertEquals("run is null", npe.getMessage());
+        }
+    }
+
+    @Test
+    public void scheduleDirectWithDelayNullRunnable() {
+        try {
+            getScheduler().scheduleDirect(null, 10, TimeUnit.MILLISECONDS);
+            fail();
+        } catch (NullPointerException npe) {
+            assertEquals("run is null", npe.getMessage());
+        }
+    }
+
+    @Test
+    public void schedulePeriodicallyDirectNullRunnable() {
+        try {
+            getScheduler().schedulePeriodicallyDirect(null, 5, 10, TimeUnit.MILLISECONDS);
+            fail();
+        } catch (NullPointerException npe) {
+            assertEquals("run is null", npe.getMessage());
+        }
+    }
+}