Remove checked exceptions from transformer interfaces. (#4710)

These functions are for transforming the stream shape, not doing work. Any operation that would throw a checked exception should happen inside the stream, not when shaping it.

Author: JakeWharton

src/main/java/io/reactivex/Completable.java

@@ -942,12 +942,7 @@ public final Throwable blockingGet(long timeout, TimeUnit unit) {
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Completable compose(CompletableTransformer transformer) {
-        try {
-            return wrap(transformer.apply(this));
-        } catch (Throwable ex) {
-            Exceptions.throwIfFatal(ex);
-            throw ExceptionHelper.wrapOrThrow(ex);
-        }
+        return wrap(transformer.apply(this));
     }
 
     /**

src/main/java/io/reactivex/CompletableTransformer.java

@@ -22,8 +22,6 @@ public interface CompletableTransformer {
      * Applies a function to the upstream Completable and returns a CompletableSource.
      * @param upstream the upstream Completable instance
      * @return the transformed CompletableSource instance
-     * @throws Exception in case the transformation throws, checked exceptions will be wrapped
-     * into a RuntimeException
      */
-    CompletableSource apply(Completable upstream) throws Exception;
+    CompletableSource apply(Completable upstream);
 }

src/main/java/io/reactivex/Flowable.java

@@ -6322,12 +6322,7 @@ public final <U> Single<U> collectInto(final U initialItem, BiConsumer<? super U
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Flowable<R> compose(FlowableTransformer<T, R> composer) {
-        try {
-            return fromPublisher(composer.apply(this));
-        } catch (Throwable ex) {
-            Exceptions.throwIfFatal(ex);
-            throw ExceptionHelper.wrapOrThrow(ex);
-        }
+        return fromPublisher(composer.apply(this));
     }
 
     /**

src/main/java/io/reactivex/FlowableTransformer.java

@@ -27,8 +27,6 @@ public interface FlowableTransformer<Upstream, Downstream> {
      * optionally different element type.
      * @param upstream the upstream Flowable instance
      * @return the transformed Publisher instance
-     * @throws Exception in case the transformation throws, checked exceptions will be wrapped
-     * into a RuntimeException
      */
-    Publisher<Downstream> apply(Flowable<Upstream> upstream) throws Exception;
+    Publisher<Downstream> apply(Flowable<Upstream> upstream);
 }

src/main/java/io/reactivex/Maybe.java

@@ -2010,12 +2010,7 @@ public final <U> Maybe<U> cast(final Class<? extends U> clazz) {
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Maybe<R> compose(MaybeTransformer<T, R> transformer) {
-        try {
-            return wrap(transformer.apply(this));
-        } catch (Throwable ex) {
-            Exceptions.throwIfFatal(ex);
-            throw ExceptionHelper.wrapOrThrow(ex);
-        }
+        return wrap(transformer.apply(this));
     }
 
     /**

src/main/java/io/reactivex/MaybeTransformer.java

@@ -25,8 +25,6 @@ public interface MaybeTransformer<Upstream, Downstream> {
      * optionally different element type.
      * @param upstream the upstream Maybe instance
      * @return the transformed MaybeSource instance
-     * @throws Exception in case the transformation throws, checked exceptions will be wrapped
-     * into a RuntimeException
      */
-    MaybeSource<Downstream> apply(Maybe<Upstream> upstream) throws Exception;
+    MaybeSource<Downstream> apply(Maybe<Upstream> upstream);
 }

src/main/java/io/reactivex/Observable.java

@@ -5531,15 +5531,9 @@ public final <U> Single<U> collectInto(final U initialValue, BiConsumer<? super
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Observable<R> compose(ObservableTransformer<T, R> composer) {
-        try {
-            return wrap(composer.apply(this));
-        } catch (Throwable ex) {
-            Exceptions.throwIfFatal(ex);
-            throw ExceptionHelper.wrapOrThrow(ex);
-        }
+        return wrap(composer.apply(this));
     }
 
-
     /**
      * Returns a new Observable that emits items resulting from applying a function that you supply to each item
      * emitted by the source ObservableSource, where that function returns an ObservableSource, and then emitting the items

src/main/java/io/reactivex/ObservableTransformer.java

@@ -25,8 +25,6 @@ public interface ObservableTransformer<Upstream, Downstream> {
      * optionally different element type.
      * @param upstream the upstream Observable instance
      * @return the transformed ObservableSource instance
-     * @throws Exception in case the transformation throws, checked exceptions will be wrapped
-     * into a RuntimeException
      */
-    ObservableSource<Downstream> apply(Observable<Upstream> upstream) throws Exception;
+    ObservableSource<Downstream> apply(Observable<Upstream> upstream);
 }

src/main/java/io/reactivex/Single.java

@@ -1473,12 +1473,7 @@ public final Single<T> hide() {
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Single<R> compose(SingleTransformer<T, R> transformer) {
-        try {
-            return wrap(transformer.apply(this));
-        } catch (Throwable ex) {
-            Exceptions.throwIfFatal(ex);
-            throw ExceptionHelper.wrapOrThrow(ex);
-        }
+        return wrap(transformer.apply(this));
     }
 
     /**

src/main/java/io/reactivex/SingleTransformer.java

@@ -25,8 +25,6 @@ public interface SingleTransformer<Upstream, Downstream> {
      * optionally different element type.
      * @param upstream the upstream Single instance
      * @return the transformed SingleSource instance
-     * @throws Exception in case the transformation throws, checked exceptions will be wrapped
-     * into a RuntimeException
      */
-    SingleSource<Downstream> apply(Single<Upstream> upstream) throws Exception;
+    SingleSource<Downstream> apply(Single<Upstream> upstream);
 }