Add Validation.getOrElseThrow(Function<E, X>) (#2695)

Author: Julien Debon

src/main/java/io/vavr/control/Validation.java

@@ -657,6 +657,33 @@ public final <U> U fold(Function<? super E, ? extends U> ifInvalid, Function<? s
         return isValid() ? ifValid.apply(get()) : ifInvalid.apply(getError());
     }
 
+    /**
+     * Gets the Valid value or throws, if the projected Validation is an Invalid.
+     *
+     * <pre>{@code
+     * Function<String, RuntimeException> exceptionFunction = RuntimeException::new;
+     * // prints "42"
+     * System.out.println(Validation.<String, Integer>valid(42).getOrElseThrow(exceptionFunction));
+     *
+     * // throws RuntimeException("no value found")
+     * Validation.invalid("no value found").getOrElseThrow(exceptionFunction);
+     * }</pre>
+     *
+     * @param <X>               a throwable type
+     * @param exceptionFunction a function which creates an exception based on an Invalid value
+     * @return the valid value, if the underlying Valdition is a Valid or else throws the exception provided by
+     * {@code exceptionFunction} by applying the Invalid value.
+     * @throws X if the projected Validation is an Invalid
+     */
+    public final <X extends Throwable> T getOrElseThrow(Function<? super E, X> exceptionFunction) throws X {
+      Objects.requireNonNull(exceptionFunction, "exceptionFunction is null");
+      if (isValid()) {
+        return get();
+      } else {
+        throw exceptionFunction.apply(getError());
+      }
+    }
+
     /**
      * Flip the valid/invalid values for this Validation. If this is a Valid&lt;E,T&gt;, returns Invalid&lt;T,E&gt;.
      * Or if this is an Invalid&lt;E,T&gt;, return a Valid&lt;T,E&gt;.

src/test/java/io/vavr/control/ValidationTest.java

@@ -300,6 +300,30 @@ public void shouldConvertFailureToU() {
         assertThat(result).isEqualTo(3);
     }
 
+
+    // getOrElseThrow(Function)
+
+    @Test
+    public void shouldReturnValidWhenGetOrElseThrowWithFunctionOnValid() {
+      final Integer actual = Validation.<String, Integer> valid(1).getOrElseThrow(s -> new RuntimeException(s));
+      assertThat(actual).isEqualTo(1);
+    }
+
+    @Test(expected = RuntimeException.class)
+    public void shouldThrowWhenGetOrElseThrowWithFunctionOnInvalid() {
+      Validation.<String, Integer> invalid("some error").getOrElseThrow(s -> new RuntimeException(s));
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void shouldThrowNullPointerExceptionWhenGetOrElseThrowNullWithFunctionOnValid() {
+      Validation.<String, Integer> valid(1).getOrElseThrow((Function<? super String, RuntimeException>) null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void shouldThrowNullPointerExceptionWhenGetOrElseThrowNullWithFunctionOnInvalid() {
+      Validation.<String, Integer> invalid("some error").getOrElseThrow((Function<? super String, RuntimeException>) null);
+    }
+
     // -- swap
 
     @Test