Throw exceptions if some of the deprecated source methods are used

app/src/main/java/eu/kanade/tachiyomi/source/Source.kt

@@ -40,23 +40,33 @@ interface Source : tachiyomi.source.Source {
      *
      * @param manga the manga to update.
      */
-    @Deprecated("Use getMangaDetails instead")
-    fun fetchMangaDetails(manga: SManga): Observable<SManga> = Observable.empty()
+    @Deprecated(
+        "Use the 1.x API instead",
+        ReplaceWith("getMangaDetails")
+    )
+    fun fetchMangaDetails(manga: SManga): Observable<SManga> = throw IllegalStateException("Not used")
 
     /**
      * Returns an observable with all the available chapters for a manga.
      *
      * @param manga the manga to update.
      */
-    @Deprecated("Use getChapterList instead")
-    fun fetchChapterList(manga: SManga): Observable<List<SChapter>> = Observable.empty()
+    @Deprecated(
+        "Use the 1.x API instead",
+        ReplaceWith("getChapterList")
+    )
+    fun fetchChapterList(manga: SManga): Observable<List<SChapter>> = throw IllegalStateException("Not used")
 
+    // TODO: remove direct usages on this method
     /**
      * Returns an observable with the list of pages a chapter has.
      *
      * @param chapter the chapter.
      */
-    @Deprecated("Use getPageList instead")
+    @Deprecated(
+        "Use the 1.x API instead",
+        ReplaceWith("getPageList")
+    )
     fun fetchPageList(chapter: SChapter): Observable<List<Page>> = Observable.empty()
 
     /**

app/src/main/java/eu/kanade/tachiyomi/ui/browse/source/globalsearch/GlobalSearchPresenter.kt

@@ -222,7 +222,7 @@ open class GlobalSearchPresenter(
                 Observable.from(first)
                     .filter { it.thumbnail_url == null && !it.initialized }
                     .map { Pair(it, source) }
-                    .concatMap { runAsObservable({ getMangaDetails(it.first, it.second) }) }
+                    .concatMap { runAsObservable { getMangaDetails(it.first, it.second) } }
                     .map { Pair(source as CatalogueSource, it) }
             }
             .onBackpressureBuffer()

app/src/main/java/eu/kanade/tachiyomi/util/lang/RxCoroutineBridge.kt

@@ -60,8 +60,8 @@ internal fun <T> CancellableContinuation<T>.unsubscribeOnCancellation(sub: Subsc
     invokeOnCancellation { sub.unsubscribe() }
 
 fun <T> runAsObservable(
+    backpressureMode: Emitter.BackpressureMode = Emitter.BackpressureMode.NONE,
     block: suspend () -> T,
-    backpressureMode: Emitter.BackpressureMode = Emitter.BackpressureMode.NONE
 ): Observable<T> {
     return Observable.create(
         { emitter ->