New feature: .mapTo(U) and .mapToVoid() for Value<T> (#3086)

Author: adamkopec

vavr/src/main/java/io/vavr/Value.java

@@ -416,6 +416,26 @@ default T getOrNull() {
         return isEmpty() ? null : get();
     }
 
+    /**
+     * Maps the underlying value to another fixed value.
+     *
+     * @param value  value to replace the contents with
+     * @param <U>    The new component type
+     * @return A new value
+     */
+    default <U> Value<U> mapTo(U value) {
+        return map((ignored) -> value);
+    }
+
+    /**
+     * Maps the underlying value to Void
+     *
+     * @return A new value of type Void
+     */
+    default Value<Void> mapToVoid() {
+        return map((ignored) -> null);
+    }
+
     /**
      * Checks if this {@code Value} is asynchronously (short: async) computed.
      * <p>

vavr/src/main/java/io/vavr/collection/TreeSet.java

@@ -1017,6 +1017,11 @@ public <U> SortedSet<U> zipWithIndex(BiFunction<? super T, ? super Integer, ? ex
         return TreeSet.ofAll(Comparators.naturalComparator(), iterator().zipWithIndex(mapper));
     }
 
+    @Override
+    public TreeSet<Void> mapToVoid() {
+        return map((o1, o2) -> 0, ignored -> null);
+    }
+
     // -- Object
 
     @Override

vavr/src/test/java/io/vavr/AbstractValueTest.java

@@ -218,6 +218,25 @@ public void shouldReturnValueWhenGetOrNullOfNonEmpty() {
         assertThat(of(1).getOrNull()).isEqualTo(1);
     }
 
+    // -- mapTo
+
+    @TestTemplate
+    public void shouldExecuteMapToCorrectly() {
+        assertThat(empty().mapTo(1)).isEqualTo(empty().mapTo(2));
+        assertThat(of(2).mapTo(1)).isEqualTo(of(3).mapTo(1));
+        assertThat(of(2).mapTo(1)).isEqualTo(of(3).map(ignored -> 1));
+        assertThat(of(3).mapTo(2)).isEqualTo(of(1).map(ignored -> 2));
+    }
+
+    // -- mapToVoid
+
+    @TestTemplate
+    public void shouldExecuteMapToVoidCorrectly() {
+        assertThat(empty().mapToVoid()).isEqualTo(empty());
+        assertThat(of(1).mapToVoid()).isEqualTo(of(1).mapTo(null));
+        assertThat(of(1).mapToVoid()).isEqualTo(of(1).map(ignored -> null));
+    }
+
     // -- forEach
 
     @TestTemplate

vavr/src/test/java/io/vavr/collection/BitSetTest.java

@@ -565,6 +565,13 @@ public void shouldReturnTailOfNonEmptyHavingReversedOrder() {
         // BitSet can't have reverse order
     }
 
+    @Test
+    @Override
+    public void shouldExecuteMapToVoidCorrectly() {
+        assertThat(empty().mapToVoid()).isEqualTo(empty());
+        assertThat(of(1).mapToVoid()).isEqualTo(of((Integer)null));
+    }
+
     // -- classes
 
     private static final class Mapper<T> implements Serializable {

vavr/src/test/java/io/vavr/collection/TreeSetTest.java

@@ -411,4 +411,11 @@ public void shouldZipAllEmptyAndNonNil() {
     @Disabled
     public void shouldZipAllNonEmptyAndNil() {
     }
+
+    @Test
+    @Override
+    public void shouldExecuteMapToVoidCorrectly() {
+        assertThat(empty().mapToVoid()).isEqualTo(empty());
+        assertThat(of(1).map(ignored -> null)).isEqualTo(of(1).mapToVoid());
+    }
 }