[result] add orElseThrow(Class) and orElseThrowUnchecked()

Split `MonResultException` into `ErrorResultException` and `UnexpectedErrorResultException`.

src/main/java/net/kemitix/mon/result/Err.java

@@ -73,8 +73,22 @@ class Err<T> implements Result<T> {
     }
 
     @Override
-    public T orElseThrow() throws MonResultException {
+    public T orElseThrow() throws Throwable {
-        throw MonResultException.with(error);
+        throw error;
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <E extends Exception> T orElseThrow(final Class<E> type) throws E {
+        if (type.isInstance(error)) {
+            throw (E) error;
+        }
+        throw UnexpectedErrorResultException.with(error);
+    }
+
+    @Override
+    public T orElseThrowUnchecked() {
+        throw ErrorResultException.with(error);
     }
 
     @Override

src/main/java/net/kemitix/mon/result/ErrorResultException.java

@@ -22,13 +22,15 @@
 package net.kemitix.mon.result;
 
 /**
- * An Unchecked wrapper for exceptions thrown within a {@code Result}.
+ * An unchecked wrapper fot exceptions thrown within a {@link Result}.
+ *
+ * <p>Used by {@link Result#orElseThrowUnchecked()} when the {@link Result} is an error.</p>
  *
  * @author Paul Campbell (pcampbell@kemitix.net)
  */
-public final class MonResultException extends RuntimeException {
+public final class ErrorResultException extends RuntimeException {
 
-    private MonResultException(final Throwable cause) {
+    private ErrorResultException(final Throwable cause) {
         super(cause);
     }
 
@@ -36,9 +38,9 @@ public final class MonResultException extends RuntimeException {
      * Creates a new object.
      *
      * @param cause the cause
-     * @return a MonResultException contain the cause
+     * @return a {@link ErrorResultException} containing the cause
      */
-    static MonResultException with(final Throwable cause) {
+    static ErrorResultException with(final Throwable cause) {
-        return new MonResultException(cause);
+        return new ErrorResultException(cause);
     }
 }

src/main/java/net/kemitix/mon/result/Result.java

@@ -99,7 +99,7 @@ public interface Result<T> extends Functor<T, Result<?>> {
     @SuppressWarnings("illegalcatch")
     public static <T> Maybe<T> toMaybe(final Result<T> result) {
         try {
-            return Maybe.just(result.orElseThrow());
+            return Maybe.just(result.orElseThrow(Exception.class));
         } catch (final Throwable throwable) {
             return Maybe.nothing();
         }
@@ -109,9 +109,28 @@ public interface Result<T> extends Functor<T, Result<?>> {
      * Extracts the successful value from the result, or throws the error Throwable.
      *
      * @return the value if a success
-     * @throws MonResultException if the result is an error
+     * @throws Throwable if the result is an error
      */
-    public abstract T orElseThrow() throws MonResultException;
+    @SuppressWarnings("illegalthrows")
+    public abstract T orElseThrow() throws Throwable;
+
+    /**
+     * Extracts the successful value from the result, or throws the error Throwable.
+     *
+     * @param type the type of checked exception that may be thrown
+     * @param <E> the type of the checked exception to throw
+     *
+     * @return the value if a success
+     * @throws E if the result is an error
+     */
+    public abstract <E extends Exception> T orElseThrow(Class<E> type) throws E;
+
+    /**
+     * Extracts the successful value from the result, or throws the error in a {@link UnexpectedErrorResultException}.
+     *
+     * @return the value if a success
+     */
+    public abstract T orElseThrowUnchecked();
 
     /**
      * Swaps the inner Result of a Maybe, so that a Result is on the outside.

src/main/java/net/kemitix/mon/result/Success.java

@@ -75,6 +75,16 @@ class Success<T> implements Result<T> {
         return value;
     }
 
+    @Override
+    public <E extends Exception> T orElseThrow(final Class<E> type) throws E {
+        return value;
+    }
+
+    @Override
+    public T orElseThrowUnchecked() {
+        return value;
+    }
+
     @Override
     public Result<T> peek(final Consumer<T> consumer) {
         consumer.accept(value);

src/main/java/net/kemitix/mon/result/UnexpectedErrorResultException.java

@@ -0,0 +1,47 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Paul Campbell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies
+ * or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.kemitix.mon.result;
+
+/**
+ * An Unchecked wrapper for unexpected exceptions thrown within a {@link Result}.
+ *
+ * <p>Used by {@link Result#orElseThrow(Class)} when the {@link Result} is an error of a different type to the
+ * parameter.</p>
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public final class UnexpectedErrorResultException extends RuntimeException {
+
+    private UnexpectedErrorResultException(final Throwable cause) {
+        super(cause);
+    }
+
+    /**
+     * Creates a new object.
+     *
+     * @param cause the cause
+     * @return a {@link UnexpectedErrorResultException} containing the cause
+     */
+    static UnexpectedErrorResultException with(final Throwable cause) {
+        return new UnexpectedErrorResultException(cause);
+    }
+}

src/test/java/net/kemitix/mon/ResultTest.java

@@ -2,6 +2,8 @@ package net.kemitix.mon;
 
 import lombok.RequiredArgsConstructor;
 import net.kemitix.mon.maybe.Maybe;
+import net.kemitix.mon.result.ErrorResultException;
+import net.kemitix.mon.result.UnexpectedErrorResultException;
 import net.kemitix.mon.result.Result;
 import org.assertj.core.api.WithAssertions;
 import org.junit.Test;
@@ -292,7 +294,53 @@ public class ResultTest implements WithAssertions {
         final RuntimeException exception = new RuntimeException();
         final Result<Integer> error = Result.error(exception);
         //when
-        assertThatThrownBy(() -> error.orElseThrow()).hasCause(exception);
+        assertThatThrownBy(() -> error.orElseThrow()).isSameAs(exception);
+    }
+
+    @Test public void okay_whenOrElseThrowT_isValue() throws Exception {
+        //given
+        final Result<Integer> ok = Result.ok(1);
+        //when
+        final Integer value = ok.orElseThrow(Exception.class);
+        //then
+        assumeThat(value).isEqualTo(1);
+    }
+
+    @Test public void errorT_whenOrElseThrowT_throwsT() {
+        //given
+        final RuntimeException exception = new RuntimeException();
+        final Result<Object> error = Result.error(exception);
+        //then
+        assertThatThrownBy(() -> error.orElseThrow(RuntimeException.class)).isSameAs(exception);
+    }
+
+    @Test public void errorR_whenOrElseThrowT_throwsWrappedR() {
+        //given
+        final IOException exception = new IOException();
+        final Result<Object> error = Result.error(exception);
+        //then
+        assertThatThrownBy(() -> error.orElseThrow(RuntimeException.class))
+                .isInstanceOf(UnexpectedErrorResultException.class)
+                .hasCause(exception);
+    }
+
+    @Test public void okay_whenOrElseThrowUnchecked_isValue() {
+        //given
+        final Result<Integer> ok = Result.ok(1);
+        //when
+        final Integer value = ok.orElseThrowUnchecked();
+        //then
+        assumeThat(value).isEqualTo(1);
+    }
+
+    @Test public void error_whenOrElseThrowUnchecked_throwsWrapped() {
+        //given
+        final IOException exception = new IOException();
+        final Result<Object> error = Result.error(exception);
+        //then
+        assertThatThrownBy(() -> error.orElseThrowUnchecked())
+                .isInstanceOf(ErrorResultException.class)
+                .hasCause(exception);
     }
 
     @Test