Merge pull request #33 from kemitix/single-consumers-for-maybe-and-result

Single consumers for maybe and result
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Paul Campbell 2018-07-07 23:16:24 +01:00 committed by GitHub
commit c8bdd77ac9
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9 changed files with 136 additions and 2 deletions

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@ -1,6 +1,13 @@
CHANGELOG CHANGELOG
========= =========
0.9.0
-----
* Add `Maybe.ifNothing(Runnable)`
* Add `Result.recover(Function)`
* Add `Result.onError(Consumer)`
0.8.0 0.8.0
----- -----

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@ -93,6 +93,11 @@ final class Just<T> implements Maybe<T> {
return this; return this;
} }
@Override
public void ifNothing(final Runnable runnable) {
// ignore - not nothing
}
@Override @Override
public void orElseThrow(final Supplier<Exception> e) { public void orElseThrow(final Supplier<Exception> e) {
// do not throw // do not throw

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@ -142,4 +142,11 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
* @return this Maybe * @return this Maybe
*/ */
Maybe<T> peek(Consumer<T> consumer); Maybe<T> peek(Consumer<T> consumer);
/**
* Run the runnable if the Maybe is a Nothing, otherwise do nothing.
*
* @param runnable the runnable to call if this is a Nothing
*/
void ifNothing(Runnable runnable);
} }

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@ -74,6 +74,11 @@ final class Nothing<T> implements Maybe<T> {
return this; return this;
} }
@Override
public void ifNothing(final Runnable runnable) {
runnable.run();
}
@Override @Override
public void orElseThrow(final Supplier<Exception> e) throws Exception { public void orElseThrow(final Supplier<Exception> e) throws Exception {
throw e.get(); throw e.get();

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@ -80,6 +80,16 @@ class Err<T> implements Result<T> {
return this; return this;
} }
@Override
public Result<T> recover(final Function<Throwable, Result<T>> f) {
return f.apply(error);
}
@Override
public void onError(final Consumer<Throwable> errorConsumer) {
errorConsumer.accept(error);
}
@Override @Override
public boolean equals(final Object other) { public boolean equals(final Object other) {
return other instanceof Err && Objects.equals(error, ((Err) other).error); return other instanceof Err && Objects.equals(error, ((Err) other).error);

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@ -94,7 +94,7 @@ public interface Result<T> extends Functor<T, Result<?>> {
* Creates a Result from the Maybe, where the Result will be an error if the Maybe is Nothing. * Creates a Result from the Maybe, where the Result will be an error if the Maybe is Nothing.
* *
* @param result the Result the might contain the value of the Result * @param result the Result the might contain the value of the Result
* @param <T> the type of the Maybe and the 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 * @return a Result containing the value of the Maybe when it is a Just, or the error when it is Nothing
*/ */
@SuppressWarnings("illegalcatch") @SuppressWarnings("illegalcatch")
@ -108,8 +108,9 @@ public interface Result<T> extends Functor<T, Result<?>> {
/** /**
* Swaps the inner Result of a Maybe, so that a Result is on the outside. * Swaps the inner Result of a Maybe, so that a Result is on the outside.
*
* @param maybeResult the Maybe the contains a Result * @param maybeResult the Maybe the contains a Result
* @param <T> the type of the value that may be in the Result * @param <T> the type of the value that may be in the Result
* @return a Result containing a Maybe, the value in the Maybe was the value in a successful Result within the * @return a Result containing a Maybe, the value in the Maybe was the value in a successful Result within the
* original Maybe. If the original Maybe is Nothing, the Result will contain Nothing. If the original Result was an * original Maybe. If the original Maybe is Nothing, the Result will contain Nothing. If the original Result was an
* error, then the Result will also be an error. * error, then the Result will also be an error.
@ -177,4 +178,22 @@ public interface Result<T> extends Functor<T, Result<?>> {
* @return this Result * @return this Result
*/ */
Result<T> peek(Consumer<T> consumer); Result<T> peek(Consumer<T> consumer);
/**
* Provide a way to attempt to recover from an error state.
*
* @param f the function to recover from the error
* @return a new Result, either a Success, or if recovery is not possible an other Err.
*/
Result<T> recover(Function<Throwable, Result<T>> f);
/**
* A handler for error states.
*
* <p>When this is an error then tne Consumer will be supplier with the error. When this is a success, then nothing
* happens.</p>
*
* @param errorConsumer the consumer to handle the error
*/
void onError(Consumer<Throwable> errorConsumer);
} }

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@ -84,6 +84,16 @@ class Success<T> implements Result<T> {
return this; return this;
} }
@Override
public Result<T> recover(final Function<Throwable, Result<T>> f) {
return this;
}
@Override
public void onError(final Consumer<Throwable> errorConsumer) {
// do nothing - this is not an error
}
@Override @Override
public boolean equals(final Object other) { public boolean equals(final Object other) {
return other instanceof Success && Objects.equals(value, ((Success) other).value); return other instanceof Success && Objects.equals(value, ((Success) other).value);

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@ -6,6 +6,7 @@ import org.junit.Test;
import java.util.Objects; import java.util.Objects;
import java.util.Optional; import java.util.Optional;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Predicate; import java.util.function.Predicate;
import java.util.stream.Stream; import java.util.stream.Stream;
@ -171,4 +172,26 @@ public class MaybeTest implements WithAssertions {
assertThat(result.toOptional()).isEmpty(); assertThat(result.toOptional()).isEmpty();
} }
@Test
public void just_ifNothing_isIgnored() {
//given
final Maybe<Integer> just = Maybe.just(1);
final AtomicBoolean capture = new AtomicBoolean(false);
//when
just.ifNothing(() -> capture.set(true));
//then
assertThat(capture).isFalse();
}
@Test
public void nothing_ifNothing_isCalled() {
//given
final Maybe<Integer> nothing = Maybe.nothing();
final AtomicBoolean capture = new AtomicBoolean(false);
//when
nothing.ifNothing(() -> capture.set(true));
//then
assertThat(capture).isTrue();
}
} }

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@ -452,6 +452,54 @@ public class ResultTest implements WithAssertions {
assertThat(peeked).isSameAs(result); assertThat(peeked).isSameAs(result);
} }
@Test public void success_whenOnError_thenIgnore() {
//given
final Result<Integer> ok = Result.ok(1);
//when
ok.onError(e -> fail("not an error"));
}
@Test public void error_whenOnError_thenConsume() {
//given
final RuntimeException exception = new RuntimeException();
final Result<Integer> error = Result.error(exception);
final AtomicReference<Throwable> capture = new AtomicReference<>();
//when
error.onError(capture::set);
//then
assertThat(capture).hasValue(exception);
}
@Test
public void success_whenRecover_thenNoChange() {
//given
final Result<Integer> ok = Result.ok(1);
//when
final Result<Integer> recovered = ok.recover(e -> Result.ok(2));
//then
recovered.peek(v -> assertThat(v).isEqualTo(1));
}
@Test
public void error_whenRecover_thenSuccess() {
//given
final Result<Integer> error = Result.error(new RuntimeException());
//when
final Result<Integer> recovered = error.recover(e -> Result.ok(2));
//then
recovered.peek(v -> assertThat(v).isEqualTo(2));
}
@Test
public void error_whenRecoverFails_thenUpdatedError() {
//given
final Result<Integer> error = Result.error(new RuntimeException("original"));
//when
final Result<Integer> recovered = error.recover(e -> Result.error(new RuntimeException("updated")));
//then
recovered.onError(e -> assertThat(e).hasMessage("updated"));
}
@RequiredArgsConstructor @RequiredArgsConstructor
private static class UseCase { private static class UseCase {