Store errors that can happen during extraction of the next page

- Closes #24

src/main/java/org/schabi/newpipe/extractor/ListExtractor.java

@@ -69,9 +69,19 @@ public abstract class ListExtractor extends Extractor {
          */
         public final String nextItemsUrl;
 
-        public NextItemsResult(List<InfoItem> nextItemsList, String nextItemsUrl) {
+        /**
+         * Errors that happened during the extraction
+         */
+        public final List<Throwable> errors;
+
+        public NextItemsResult(InfoItemCollector collector, String nextItemsUrl) {
+            this(collector.getItemList(), nextItemsUrl, collector.getErrors());
+        }
+
+        public NextItemsResult(List<InfoItem> nextItemsList, String nextItemsUrl, List<Throwable> errors) {
             this.nextItemsList = nextItemsList;
             this.nextItemsUrl = nextItemsUrl;
+            this.errors = errors;
         }
 
         public boolean hasMoreStreams() {

src/main/java/org/schabi/newpipe/extractor/services/soundcloud/SoundcloudChannelExtractor.java

@@ -102,6 +102,6 @@ public class SoundcloudChannelExtractor extends ChannelExtractor {
         StreamInfoItemCollector collector = new StreamInfoItemCollector(getServiceId());
         nextStreamsUrl = SoundcloudParsingHelper.getStreamsFromApiMinItems(15, collector, nextStreamsUrl);
 
-        return new NextItemsResult(collector.getItemList(), nextStreamsUrl);
+        return new NextItemsResult(collector, nextStreamsUrl);
     }
 }

src/main/java/org/schabi/newpipe/extractor/services/soundcloud/SoundcloudPlaylistExtractor.java

@@ -104,6 +104,6 @@ public class SoundcloudPlaylistExtractor extends PlaylistExtractor {
         StreamInfoItemCollector collector = new StreamInfoItemCollector(getServiceId());
         nextStreamsUrl = SoundcloudParsingHelper.getStreamsFromApiMinItems(15, collector, nextStreamsUrl);
 
-        return new NextItemsResult(collector.getItemList(), nextStreamsUrl);
+        return new NextItemsResult(collector, nextStreamsUrl);
     }
 }

src/main/java/org/schabi/newpipe/extractor/services/youtube/YoutubeChannelExtractor.java

@@ -153,7 +153,7 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
         setupNextStreamsAjax(NewPipe.getDownloader());
         collectStreamsFrom(collector, nextStreamsAjax.select("body").first());
 
-        return new NextItemsResult(collector.getItemList(), nextStreamsUrl);
+        return new NextItemsResult(collector, nextStreamsUrl);
     }
 
     private void setupNextStreamsAjax(Downloader downloader) throws IOException, ReCaptchaException, ParsingException {

src/main/java/org/schabi/newpipe/extractor/services/youtube/YoutubePlaylistExtractor.java

@@ -157,7 +157,7 @@ public class YoutubePlaylistExtractor extends PlaylistExtractor {
         setupNextStreamsAjax(NewPipe.getDownloader());
         collectStreamsFrom(collector, nextStreamsAjax.select("tbody[id=\"pl-load-more-destination\"]").first());
 
-        return new NextItemsResult(collector.getItemList(), nextStreamsUrl);
+        return new NextItemsResult(collector, nextStreamsUrl);
     }
 
     private void setupNextStreamsAjax(Downloader downloader) throws IOException, ReCaptchaException, ParsingException {

src/test/java/org/schabi/newpipe/extractor/services/soundcloud/SoundcloudChannelExtractorTest.java

@@ -3,6 +3,7 @@ package org.schabi.newpipe.extractor.services.soundcloud;
 import org.junit.Before;
 import org.junit.Test;
 import org.schabi.newpipe.Downloader;
+import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.channel.ChannelExtractor;
 
@@ -70,7 +71,9 @@ public class SoundcloudChannelExtractorTest {
     public void testGetNextStreams() throws Exception {
         // Setup the streams
         extractor.getStreams();
-        assertTrue("extractor didn't have next streams", !extractor.getNextStreams().nextItemsList.isEmpty());
+        ListExtractor.NextItemsResult nextItemsResult = extractor.getNextStreams();
+        assertTrue("extractor didn't have next streams", !nextItemsResult.nextItemsList.isEmpty());
+        assertTrue("errors occurred during extraction of the next streams", nextItemsResult.errors.isEmpty());
         assertTrue("extractor didn't have more streams after getNextStreams", extractor.hasMoreStreams());
     }
 

src/test/java/org/schabi/newpipe/extractor/services/soundcloud/SoundcloudPlaylistExtractorTest.java

@@ -4,6 +4,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.schabi.newpipe.Downloader;
 import org.schabi.newpipe.extractor.NewPipe;
+import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.playlist.PlaylistExtractor;
 
 import static org.junit.Assert.*;
@@ -79,4 +80,15 @@ public class SoundcloudPlaylistExtractorTest {
         extractor.getStreams();
         assertTrue("extractor didn't have more streams", !extractor.hasMoreStreams());
     }
+
+    @Test(expected = ExtractionException.class)
+    public void testGetNextStreamsNonExistent() throws Exception {
+        // Setup the streams
+        extractor.getStreams();
+
+        // This playlist don't have more streams, it should throw an error
+        extractor.getNextStreams();
+
+        fail("Expected exception wasn't thrown");
+    }
 }

src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeChannelExtractorTest.java

@@ -3,6 +3,7 @@ package org.schabi.newpipe.extractor.services.youtube;
 import org.junit.Before;
 import org.junit.Test;
 import org.schabi.newpipe.Downloader;
+import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.channel.ChannelExtractor;
 
@@ -99,7 +100,9 @@ public class YoutubeChannelExtractorTest {
     public void testGetNextStreams() throws Exception {
         // Setup the streams
         extractor.getStreams();
-        assertTrue("extractor didn't have next streams", !extractor.getNextStreams().nextItemsList.isEmpty());
+        ListExtractor.NextItemsResult nextItemsResult = extractor.getNextStreams();
+        assertTrue("extractor didn't have next streams", !nextItemsResult.nextItemsList.isEmpty());
+        assertTrue("errors occurred during extraction of the next streams", nextItemsResult.errors.isEmpty());
         assertTrue("extractor didn't have more streams after getNextStreams", extractor.hasMoreStreams());
     }
 

src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubePlaylistExtractorTest.java

@@ -3,6 +3,7 @@ package org.schabi.newpipe.extractor.services.youtube;
 import org.junit.Before;
 import org.junit.Test;
 import org.schabi.newpipe.Downloader;
+import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.playlist.PlaylistExtractor;
 
@@ -89,7 +90,9 @@ public class YoutubePlaylistExtractorTest {
     public void testGetNextStreams() throws Exception {
         // Setup the streams
         extractor.getStreams();
-        assertTrue("extractor didn't have next streams", !extractor.getNextStreams().nextItemsList.isEmpty());
+        ListExtractor.NextItemsResult nextItemsResult = extractor.getNextStreams();
+        assertTrue("extractor didn't have next streams", !nextItemsResult.nextItemsList.isEmpty());
+        assertTrue("errors occurred during extraction of the next streams", nextItemsResult.errors.isEmpty());
         assertTrue("extractor didn't have more streams after getNextStreams", extractor.hasMoreStreams());
     }