| // Copyright 2024 The Bazel Authors. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| package com.google.devtools.build.lib.util; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| /** |
| * Contains a value, or the exception encountered while obtaining that value. |
| * |
| * <p>This class is intended to be used when an operation computes multiple values, some of which |
| * may have succeeded and others may have failed, and it is necessary to return all of these values |
| * or failures without throwing at the first failure encountered. |
| */ |
| // TODO(b/331799946): try to consolidate Bazel's "value or exception" sum types into this one |
| public abstract sealed class ValueOrException<V, E extends Exception> { |
| |
| // Must be initialized through ofValue or ofException |
| private ValueOrException() {} |
| |
| /** Constructs a ValueOrException holding a non-null value. */ |
| public static <V, E extends Exception> ValueOrException<V, E> ofValue(V value) { |
| return new OfValue<>(checkNotNull(value)); |
| } |
| |
| /** Constructs a ValueOrException holding an exception. */ |
| public static <V, E extends Exception> ValueOrException<V, E> ofException(E exception) { |
| return new OfException<>(checkNotNull(exception)); |
| } |
| |
| /** Returns true if the ValueOrException holds a value. */ |
| public abstract boolean isPresent(); |
| |
| /** |
| * Returns the value if the ValueOrException holds a value. |
| * |
| * @throws E if the ValueOrException holds an exception. |
| */ |
| public abstract V get() throws E; |
| |
| /** |
| * A variant of {@link #get} which throws an unchecked exception. |
| * |
| * @throws IllegalStateException if the ValueOrException holds an exception. |
| */ |
| public V getUnchecked() { |
| try { |
| return get(); |
| } catch (Exception e) { |
| throw new IllegalStateException(e); |
| } |
| } |
| |
| /** |
| * Returns the exception if the ValueOrException holds an exception. |
| * |
| * @throws IllegalStateException if the ValueOrException does not hold an exception. |
| */ |
| public abstract E getException(); |
| |
| private static final class OfValue<V, E extends Exception> extends ValueOrException<V, E> { |
| private final V value; |
| |
| OfValue(V value) { |
| this.value = value; |
| } |
| |
| @Override |
| public boolean isPresent() { |
| return true; |
| } |
| |
| @Override |
| public V get() { |
| return value; |
| } |
| |
| @Override |
| public E getException() { |
| throw new IllegalStateException( |
| "ValueOrException.getException() cannot be called on a ValueOrException holding a value"); |
| } |
| |
| @Override |
| public String toString() { |
| return String.format("ValueOrException.OfValue[%s]", value); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>Value equality semantics; two {@code OfValue} objects are equal iff their contained values |
| * are equal. |
| */ |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) { |
| return true; |
| } |
| if (!(o instanceof OfValue<?, ?> rhs)) { |
| return false; |
| } |
| return value.equals(rhs.value); |
| } |
| |
| @Override |
| public int hashCode() { |
| return value.hashCode(); |
| } |
| } |
| |
| private static final class OfException<V, E extends Exception> extends ValueOrException<V, E> { |
| private final E exception; |
| |
| OfException(E exception) { |
| this.exception = checkNotNull(exception); |
| } |
| |
| @Override |
| public boolean isPresent() { |
| return false; |
| } |
| |
| @Override |
| public V get() throws E { |
| throw exception; |
| } |
| |
| @Override |
| public E getException() { |
| return exception; |
| } |
| |
| @Override |
| public String toString() { |
| return String.format("ValueOrException.OfException[%s]", exception); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>Value equality semantics; two {@code OfException} objects are equal iff their contained |
| * exception objects are equal. |
| */ |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) { |
| return true; |
| } |
| if (!(o instanceof OfException<?, ?> rhs)) { |
| return false; |
| } |
| return exception.equals(rhs.exception); |
| } |
| |
| @Override |
| public int hashCode() { |
| return exception.hashCode(); |
| } |
| } |
| } |