Func0 can transparently implement java.util.concurrent.Callable.

rxjava-contrib/rxjava-async-util/src/main/java/rx/util/async/Async.java

@@ -1596,9 +1596,13 @@ public static <R> Observable<R> fromAction(Action0 action, R result) {
      * @see #start(rx.functions.Func0) 
      * @see #fromCallable(java.util.concurrent.Callable) 
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Async-Operators#fromfunc0">RxJava Wiki: fromFunc0()</a>
+     *
+     * @deprecated  Unnecessary now that Func0 extends Callable. Just call
+     *              {@link #fromCallable(Callable)} instead.
      */
+    @Deprecated
     public static <R> Observable<R> fromFunc0(Func0<? extends R> function) {
-        return fromFunc0(function, Schedulers.computation());
+        return fromCallable(function);
     }
 
     /**
@@ -1674,9 +1678,13 @@ public static <R> Observable<R> fromAction(Action0 action, R result, Scheduler s
      * @see #start(rx.functions.Func0) 
      * @see #fromCallable(java.util.concurrent.Callable) 
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Async-Operators#fromfunc0">RxJava Wiki: fromFunc0()</a>
+     *
+     * @deprecated  Unnecessary now that Func0 extends Callable. Just call
+     *              {@link #fromCallable(Callable, Scheduler)} instead.
      */
+    @Deprecated
     public static <R> Observable<R> fromFunc0(Func0<? extends R> function, Scheduler scheduler) {
-        return Observable.create(OperationFromFunctionals.fromFunc0(function)).subscribeOn(scheduler);
+        return fromCallable(function, scheduler);
     }
 
     /**

rxjava-contrib/rxjava-async-util/src/main/java/rx/util/async/operators/OperationFromFunctionals.java

@@ -38,22 +38,28 @@ public final class OperationFromFunctionals {
     public static <R> OnSubscribeFunc<R> fromAction(Action0 action, R result) {
         return new InvokeAsync<R>(Actions.toFunc(action, result));
     }
-
-    /** Subscriber function that invokes a function and returns its value. */
+
+    /**
+     * Subscriber function that invokes a function and returns its value.
+     *
+     * @deprecated  Unnecessary now that Func0 extends Callable. Just call
+     *              {@link #fromCallable(Callable)} instead.
+     */
+    @Deprecated
     public static <R> OnSubscribeFunc<R> fromFunc0(Func0<? extends R> function) {
-        return new InvokeAsync<R>(function);
+        return fromCallable(function);
     }
 
     /** 
      * Subscriber function that invokes the callable and returns its value or
      * propagates its checked exception.
      */
     public static <R> OnSubscribeFunc<R> fromCallable(Callable<? extends R> callable) {
-        return new InvokeAsyncCallable<R>(callable);
+        return new InvokeAsync<R>(callable);
     }
     /** Subscriber function that invokes a runnable and returns the given result. */
     public static <R> OnSubscribeFunc<R> fromRunnable(final Runnable run, final R result) {
-        return new InvokeAsync(new Func0<R>() {
+        return new InvokeAsync<R>(new Func0<R>() {
             @Override
             public R call() {
                 run.run();
@@ -62,38 +68,13 @@ public R call() {
         });
     }
 
-    /**
-     * Invokes a function when an observer subscribes.
-     * @param <R> the return type
-     */
-    static final class InvokeAsync<R> implements OnSubscribeFunc<R> {
-        final Func0<? extends R> function;
-        public InvokeAsync(Func0<? extends R> function) {
-            if (function == null) {
-                throw new NullPointerException("function");
-            }
-            this.function = function;
-        }
-        @Override
-        public Subscription onSubscribe(Observer<? super R> t1) {
-            Subscription s = Subscriptions.empty();
-            try {
-                t1.onNext(function.call());
-            } catch (Throwable t) {
-                t1.onError(t);
-                return s;
-            }
-            t1.onCompleted();
-            return s;
-        }
-    }
     /**
      * Invokes a java.util.concurrent.Callable when an observer subscribes.
      * @param <R> the return type
      */
-    static final class InvokeAsyncCallable<R> implements OnSubscribeFunc<R> {
+    static final class InvokeAsync<R> implements OnSubscribeFunc<R> {
         final Callable<? extends R> callable;
-        public InvokeAsyncCallable(Callable<? extends R> callable) {
+        public InvokeAsync(Callable<? extends R> callable) {
             if (callable == null) {
                 throw new NullPointerException("function");
             }

rxjava-contrib/rxjava-async-util/src/test/java/rx/util/async/operators/OperationFromFunctionalsTest.java

@@ -110,6 +110,13 @@ public void call() {
 
         testRunShouldThrow(source, RuntimeException.class);
     }
+
+    /**
+     * @deprecated  {@link Func0} now extends {@link Callable}, so
+     *              {@link Async#fromFunc0(Func0)} is unnecessary. Once it's
+     *              removed, this test can be removed as well.
+     */
+    @Deprecated
     @Test
     public void testFromFunc0() {
         Func0<Integer> func = new Func0<Integer>() {
@@ -139,7 +146,14 @@ public Integer call() {
             verify(observer, never()).onError(any(Throwable.class));
         }
     }
-
+
+    /**
+     * @deprecated  {@link Func0} now extends {@link Callable}, so
+     *              {@link Async#fromFunc0(Func0, rx.Scheduler)} is
+     *              unnecessary. Once it's removed, this test can be removed
+     *              as well.
+     */
+    @Deprecated
     @Test
     public void testFromFunc0Throws() {
         Func0<Integer> func = new Func0<Integer>() {

rxjava-core/src/main/java/rx/functions/Func0.java

@@ -15,6 +15,9 @@
  */
 package rx.functions;
 
-public interface Func0<R> extends Function {
+import java.util.concurrent.Callable;
+
+public interface Func0<R> extends Function, Callable<R> {
+    @Override
     public R call();
-}
+}