adding tests

RxJavaExtensions/src/androidTest/java/it/sephiroth/android/rxjava3/extensions/SingleAndroidTest.kt

@@ -2,10 +2,8 @@ package it.sephiroth.android.rxjava3.extensions
 
 import android.os.Looper
 import androidx.test.ext.junit.runners.AndroidJUnit4
-import io.reactivex.rxjava3.core.Observable
 import io.reactivex.rxjava3.core.Single
 import io.reactivex.rxjava3.schedulers.Schedulers
-import it.sephiroth.android.rxjava3.extensions.observable.firstInList
 import it.sephiroth.android.rxjava3.extensions.observers.AutoDisposableSingleObserver
 import it.sephiroth.android.rxjava3.extensions.single.*
 import org.junit.Assert
@@ -145,6 +143,14 @@ class SingleAndroidTest {
         Single.just(listOf(null, null)).asObservable().test().await().assertComplete().assertNoValues()
     }
 
+    @Test
+    fun test011() {
+        Single.just(listOf(1, 2, 3, 4, 5)).firstInList { it % 2 == 0 }.test().await().assertComplete().assertValue(2)
+        Single.just(emptyList<Int>()).firstInList { it % 2 == 0 }.test().await().assertComplete().assertNoValues()
+        Single.just(listOf(null, 1, 2)).firstInList { null != it && it % 2 == 0 }.test().await().assertComplete().assertValue(2)
+        Single.just(listOf<Int?>(null, null)).firstInList { null != it && it % 2 == 0 }.test().await().assertComplete().assertNoValues()
+    }
+
     companion object {
         private lateinit var ioThread: Thread
         private lateinit var singleThread: Thread

RxJavaExtensions/src/main/java/it/sephiroth/android/rxjava3/extensions/flowable/Flowable.kt

@@ -42,6 +42,8 @@ import it.sephiroth.android.rxjava3.extensions.observable.autoSubscribe
 import it.sephiroth.android.rxjava3.extensions.observers.AutoDisposableObserver
 import it.sephiroth.android.rxjava3.extensions.observers.AutoDisposableSubscriber
 import it.sephiroth.android.rxjava3.extensions.operators.FlowableMapNotNull
+import it.sephiroth.android.rxjava3.extensions.single.firstInList
+import it.sephiroth.android.rxjava3.extensions.single.firstInListNotNull
 import java.util.*
 import java.util.concurrent.TimeUnit
 import java.util.function.Predicate
@@ -236,7 +238,7 @@ fun <T> Flowable<T>.toSingle(): Single<T> where T : Any {
  * @since 3.0.5
  */
 fun <T> Flowable<List<T>>.firstInList(): Maybe<T> {
-    return this.firstOrError().filter { it.isNotEmpty() }.map { it.first() }
+    return this.toSingle().firstInList()
 }
 
 
@@ -247,7 +249,7 @@ fun <T> Flowable<List<T>>.firstInList(): Maybe<T> {
  * @since 3.0.5
  */
 fun <T> Flowable<List<T>>.firstInListNotNull(): Maybe<T> {
-    return this.firstOrError().filter { it.isNotEmpty() }.mapOptional { Optional.ofNullable(it.firstOrNull { item -> item != null }) }
+    return this.toSingle().firstInListNotNull()
 }
 
 
@@ -258,5 +260,5 @@ fun <T> Flowable<List<T>>.firstInListNotNull(): Maybe<T> {
  * @since 3.0.5
  */
 fun <T> Flowable<List<T>>.firstInList(predicate: Predicate<T>): Maybe<T> {
-    return this.firstOrError().mapOptional { list -> Optional.ofNullable(list.firstOrNull { item -> predicate.test(item) }) }
+    return this.toSingle().firstInList(predicate)
 }

RxJavaExtensions/src/main/java/it/sephiroth/android/rxjava3/extensions/observable/Observable.kt

@@ -42,6 +42,8 @@ import io.reactivex.rxjava3.schedulers.Schedulers
 import it.sephiroth.android.rxjava3.extensions.MuteException
 import it.sephiroth.android.rxjava3.extensions.observers.AutoDisposableObserver
 import it.sephiroth.android.rxjava3.extensions.operators.ObservableMapNotNull
+import it.sephiroth.android.rxjava3.extensions.single.firstInList
+import it.sephiroth.android.rxjava3.extensions.single.firstInListNotNull
 import java.util.*
 import java.util.concurrent.TimeUnit
 import java.util.function.Predicate
@@ -68,7 +70,7 @@ fun <T> Observable<T>.toSingle(): Single<T> where T : Any {
  * if the list contains at least one element.
  */
 fun <T> Observable<List<T>>.firstInList(): Maybe<T> {
-    return this.firstOrError().filter { it.isNotEmpty() }.map { it.first() }
+    return this.toSingle().firstInList()
 }
 
 /**
@@ -78,7 +80,7 @@ fun <T> Observable<List<T>>.firstInList(): Maybe<T> {
  * @since 3.0.5
  */
 fun <T> Observable<List<T>>.firstInListNotNull(): Maybe<T> {
-    return this.firstOrError().filter { it.isNotEmpty() }.mapOptional { Optional.ofNullable(it.firstOrNull { item -> item != null }) }
+    return this.toSingle().firstInListNotNull()
 }
 
 /**
@@ -88,7 +90,7 @@ fun <T> Observable<List<T>>.firstInListNotNull(): Maybe<T> {
  * @since 3.0.5
  */
 fun <T> Observable<List<T>>.firstInList(predicate: Predicate<T>): Maybe<T> {
-    return this.firstOrError().mapOptional { list -> Optional.ofNullable(list.firstOrNull { item -> predicate.test(item) }) }
+    return this.toSingle().firstInList(predicate)
 }
 
 

RxJavaExtensions/src/main/java/it/sephiroth/android/rxjava3/extensions/single/Single.kt

@@ -37,6 +37,7 @@ import io.reactivex.rxjava3.core.Single
 import io.reactivex.rxjava3.functions.Function
 import it.sephiroth.android.rxjava3.extensions.observers.AutoDisposableSingleObserver
 import java.util.*
+import java.util.function.Predicate
 
 
 /**
@@ -46,25 +47,34 @@ import java.util.*
  */
 
 /**
- * If the [Single] returns a [List] of items, this transformer will
- * convert the source into a [Maybe] which will emit the very first item of the list,
+ * If the source [Single] returns a [List] of items, this transformer will
+ * convert the Single into a [Maybe] which emit the very first item of the list,
  * if the list contains at least one element.
  */
 fun <T> Single<List<T>>.firstInList(): Maybe<T> {
     return this.filter { it.isNotEmpty() }.map { it.first() }
 }
 
-
 /**
- * If the [Single] returns a [List] of items, this transformer will
- * convert the source into a [Maybe] which will emit the very first non null item of the list.
+ * If the source [Single] returns a [List] of items, this transformer will
+ * convert the Single into a [Maybe] which emit the very first non null item of the list.
  *
  * @since 3.0.5
  */
 fun <T> Single<List<T>>.firstInListNotNull(): Maybe<T> {
     return this.filter { it.isNotEmpty() }.mapOptional { Optional.ofNullable(it.firstOrNull { item -> item != null }) }
 }
 
+/**
+ * If the source [Single] returns a [List] of items, this transformer will
+ * convert the Single into a [Maybe] which emit the very first item that match the predicate.
+ *
+ * @since 3.0.5
+ */
+fun <T> Single<List<T>>.firstInList(predicate: Predicate<T>): Maybe<T> {
+    return this.mapOptional { list -> Optional.ofNullable(list.firstOrNull { item -> predicate.test(item) }) }
+}
+
 /**
  * Subscribe to this [Single] using an instance of the [AutoDisposableSingleObserver]
  */