add missing null checks

Author: jhspetersson

src/main/java/io/github/jhspetersson/packrat/Packrat.java

@@ -575,6 +575,7 @@ public final class Packrat {
      */
     @NonNull
     public static <T> Gatherer<T, ?, T> mapWhile(@NonNull Function<? super T, ? extends T> mapper, @NonNull Predicate<? super T> predicate) {
+        Objects.requireNonNull(predicate, "predicate cannot be null");
         return new MapWhileUntilGatherer<>(mapper, predicate);
     }
 
@@ -590,6 +591,7 @@ public final class Packrat {
      */
     @NonNull
     public static <T> Gatherer<T, ?, T> mapUntil(@NonNull Function<? super T, ? extends T> mapper, @NonNull Predicate<? super T> predicate) {
+        Objects.requireNonNull(predicate, "predicate cannot be null");
         return new MapWhileUntilGatherer<>(mapper, null, predicate);
     }
 

src/test/java/io/github/jhspetersson/packrat/MapWhileUntilTest.java

@@ -6,6 +6,7 @@
 import java.util.stream.IntStream;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 public class MapWhileUntilTest {
     @Test
@@ -19,4 +20,24 @@ public void mapUntilTest() {
         var mapped = IntStream.rangeClosed(1, 10).boxed().gather(Packrat.mapUntil(n -> n * 10, n -> n == 6)).toList();
         assertEquals(List.of(10, 20, 30, 40, 50, 6, 7, 8, 9, 10), mapped);
     }
+
+    @Test
+    public void mapWhileNullPredicateThrows() {
+        assertThrows(NullPointerException.class, () -> Packrat.mapWhile(n -> (Integer) n * 10, null));
+    }
+
+    @Test
+    public void mapUntilNullPredicateThrows() {
+        assertThrows(NullPointerException.class, () -> Packrat.mapUntil(n -> (Integer) n * 10, null));
+    }
+
+    @Test
+    public void mapWhileNullMapperThrows() {
+        assertThrows(NullPointerException.class, () -> Packrat.<Integer>mapWhile(null, n -> n <= 3));
+    }
+
+    @Test
+    public void mapUntilNullMapperThrows() {
+        assertThrows(NullPointerException.class, () -> Packrat.<Integer>mapUntil(null, n -> n == 6));
+    }
 }