Add thenWith(Function)
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6 changed files with 137 additions and 3 deletions
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@ -5,6 +5,7 @@ CHANGELOG
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------
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* Add `andThen(Function)`
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* Add `thenWith(Function)`
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0.9.0
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-----
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@ -96,6 +96,11 @@ class Err<T> implements Result<T> {
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return Result.error(error);
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}
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@Override
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public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
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return this;
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}
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@Override
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public boolean equals(final Object other) {
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return other instanceof Err && Objects.equals(error, ((Err) other).error);
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@ -202,7 +202,6 @@ public interface Result<T> extends Functor<T, Result<?>> {
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*
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* <p>Combination of {@link #flatMap(Function)} and {@link #of(Callable)}.</p>
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*
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* <p>Syntax is:</p>
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* <pre><code>
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* Integer doSomething() {...}
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* String doSomethingElse(final Integer value) {...}
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@ -212,9 +211,29 @@ public interface Result<T> extends Functor<T, Result<?>> {
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*
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* <p>When the Result is an Err, then the original error is carried over and the Callable is never called.</p>
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*
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* @param f the function to map the Success value to the Callable
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* @param f the function to map the Success value into the Callable
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* @param <R> the type of the final Result
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* @return a new Result
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*/
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<R> Result<R> andThen(Function<T, Callable<R>> f);
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/**
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* Perform the continuation with the current Result value then return the current Result, assuming there was no
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* error in the continuation.
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*
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* <pre><code>
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* Integer doSomething() {...}
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* void doSomethingElse(final Integer value) {...}
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* Result<Integer> r = Result.of(() -> doSomething())
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* .thenWith(value -> () -> doSomethingElse(value));
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* </code></pre>
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*
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* <p>Where the Result is an Err, then the Result is returned immediately and the continuation is ignored.</p>
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* <p>Where the Result is a Success, then if an exception is thrown by the continuation the Result returned will be
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* a new error Result containing that exception, otherwise the original Result will be returned.</p>
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*
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* @param f the function to map the Success value into the result continuation
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* @return the Result or a new error Result
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*/
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Result<T> thenWith(Function<T, WithResultContinuation<T>> f);
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}
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@ -100,6 +100,11 @@ class Success<T> implements Result<T> {
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return Result.of(f.apply(value));
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}
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@Override
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public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
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return f.apply(value).call(this);
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}
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@Override
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public boolean equals(final Object other) {
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return other instanceof Success && Objects.equals(value, ((Success) other).value);
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@ -0,0 +1,49 @@
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/**
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* The MIT License (MIT)
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*
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* Copyright (c) 2017 Paul Campbell
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
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* and associated documentation files (the "Software"), to deal in the Software without restriction,
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* including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all copies
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* or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
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* AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package net.kemitix.mon.result;
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/**
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* A Callable-like interface for performing an action with a Result that, if there are no errors is returned as-is, but
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* if there is an error then a new error Result is returned.
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*
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* @param <T> the type of the current Result value
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*/
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@FunctionalInterface
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public interface WithResultContinuation<T> {
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/**
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* Method to make use of the Result value.
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*
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* @throws Exception to replace the current Result with an error
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*/
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void run() throws Exception;
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@SuppressWarnings({"illegalcatch", "javadocmethod"})
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default Result<T> call(final Result<T> currentResult) {
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try {
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run();
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} catch (Throwable e) {
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return Result.error(e);
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}
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return currentResult;
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}
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}
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@ -540,7 +540,7 @@ public class ResultTest implements WithAssertions {
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}
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@Test
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public void error_andThenError_thenError() {
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public void error_andThenError_thenOriginalError() {
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//given
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final RuntimeException exception1 = new RuntimeException();
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final Result<Object> error = Result.error(exception1);
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@ -553,6 +553,61 @@ public class ResultTest implements WithAssertions {
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result.onError(e -> assertThat(e).isSameAs(exception1));
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}
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@Test
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public void success_whenThenWith_whenOkay_thenSuccess() {
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//given
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final Result<Integer> ok = Result.ok(1);
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//when
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final Result<Integer> result = ok.thenWith(v -> () -> {
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// do something with v
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});
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//then
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assertThat(result.isOkay()).isTrue();
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result.peek(v -> assertThat(v).isEqualTo(1));
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}
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@Test
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public void success_whenThenWith_whenError_thenError() {
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//given
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final Result<Integer> ok = Result.ok(1);
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final RuntimeException exception = new RuntimeException();
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//when
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final Result<Integer> result = ok.thenWith(v -> () -> {
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throw exception;
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});
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//then
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assertThat(result.isError()).isTrue();
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result.onError(e -> assertThat(e).isSameAs(exception));
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}
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@Test
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public void error_whenThenWith_whenOkay_thenError() {
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//given
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final RuntimeException exception = new RuntimeException();
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final Result<Integer> error = Result.error(exception);
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//when
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final Result<Integer> result = error.thenWith(v -> () -> {
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// do something with v
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});
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//then
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assertThat(result.isError()).isTrue();
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result.onError(e -> assertThat(e).isSameAs(exception));
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}
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@Test
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public void error_whenThenWith_whenError_thenOriginalError() {
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//given
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final RuntimeException exception = new RuntimeException();
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final Result<Integer> error = Result.error(exception);
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//when
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final Result<Integer> result = error.thenWith(v -> () -> {
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throw new RuntimeException();
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});
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//then
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assertThat(result.isError()).isTrue();
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result.onError(e -> assertThat(e).isSameAs(exception));
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}
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@RequiredArgsConstructor
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private static class UseCase {
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