Merge pull request #54 from kemitix/result-orelsethrow-checkederrorresultexception

[result] orElseThrow() throws error within a CheckedErrorResultException

CHANGELOG

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+1.2.0
+-----
+
+* [result] orElseThrow() throws error within a CheckedErrorResultException
+
 1.1.0
 -----
 

README.org

@@ -821,7 +821,7 @@
 **** =T orElseThrow()=
 
      Extracts the successful value from the result, or throws the error
-     =Throwable=.
+     within a =CheckedErrorResultException=.
 
      #+BEGIN_SRC java
      final Integer result = Result.of(() -> getValue())

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

@@ -0,0 +1,46 @@
+/**
+ * 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;
+
+/**
+ * A checked wrapper for exceptions thrown within a {@link Result}.
+ *
+ * <p>Used by {@link Result#orElseThrow()} when the {@link Result} is an error.</p>
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public final class CheckedErrorResultException extends Exception {
+
+    private CheckedErrorResultException(final Throwable cause) {
+        super(cause);
+    }
+
+    /**
+     * Creates a new object.
+     *
+     * @param cause the cause
+     * @return a {@link CheckedErrorResultException} containing the cause
+     */
+    static CheckedErrorResultException with(final Throwable cause) {
+        return new CheckedErrorResultException(cause);
+    }
+}

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

@@ -73,8 +73,8 @@ class Err<T> implements Result<T> {
     }
 
     @Override
-    public T orElseThrow() throws Throwable {
-        throw error;
+    public T orElseThrow() throws CheckedErrorResultException {
+        throw CheckedErrorResultException.with(error);
     }
 
     @Override

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

@@ -22,7 +22,7 @@
 package net.kemitix.mon.result;
 
 /**
- * An unchecked wrapper fot exceptions thrown within a {@link Result}.
+ * An unchecked wrapper for exceptions thrown within a {@link Result}.
  *
  * <p>Used by {@link Result#orElseThrowUnchecked()} when the {@link Result} is an error.</p>
  *

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

@@ -96,23 +96,21 @@ public interface Result<T> extends Functor<T, Result<?>> {
      * @param <T>    the type of the Maybe and the Result
      * @return a Result containing the value of the Maybe when it is a Just, or the error when it is Nothing
      */
-    @SuppressWarnings("illegalcatch")
     public static <T> Maybe<T> toMaybe(final Result<T> result) {
         try {
             return Maybe.just(result.orElseThrow());
-        } catch (final Throwable throwable) {
+        } catch (final CheckedErrorResultException throwable) {
             return Maybe.nothing();
         }
     }
 
     /**
-     * Extracts the successful value from the result, or throws the error Throwable.
+     * Extracts the successful value from the result, or throws the error within a {@link CheckedErrorResultException}.
      *
      * @return the value if a success
-     * @throws Throwable if the result is an error
+     * @throws CheckedErrorResultException if the result is an error
      */
-    @SuppressWarnings("illegalthrows")
-    public abstract T orElseThrow() throws Throwable;
+    public abstract T orElseThrow() throws CheckedErrorResultException;
 
     /**
      * Extracts the successful value from the result, or throws the error Throwable.

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

@@ -2,6 +2,7 @@ package net.kemitix.mon;
 
 import lombok.RequiredArgsConstructor;
 import net.kemitix.mon.maybe.Maybe;
+import net.kemitix.mon.result.CheckedErrorResultException;
 import net.kemitix.mon.result.ErrorResultException;
 import net.kemitix.mon.result.UnexpectedErrorResultException;
 import net.kemitix.mon.result.Result;
@@ -294,7 +295,9 @@ public class ResultTest implements WithAssertions {
         final RuntimeException exception = new RuntimeException();
         final Result<Integer> error = Result.error(exception);
         //when
-        assertThatThrownBy(() -> error.orElseThrow()).isSameAs(exception);
+        assertThatThrownBy(() -> error.orElseThrow())
+                .isInstanceOf(CheckedErrorResultException.class)
+                .hasCause(exception);
     }
 
     @Test public void okay_whenOrElseThrowT_isValue() throws Exception {