com.google.gerrit.extensions.common.ChangeInfoDiffer Maven / Gradle / Ivy
// Copyright (C) 2021 The Android Open Source Project
//
// 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.gerrit.extensions.common;
import static com.google.common.collect.ImmutableList.toImmutableList;
import static java.util.Arrays.stream;
import static java.util.stream.Collectors.groupingBy;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.sql.Timestamp;
import java.util.Collection;
import java.util.List;
import java.util.Map;
/**
* Gets the differences between two {@link ChangeInfo}s.
*
* This must be in package {@code com.google.gerrit.extensions.common} for access to protected
* constructors.
*
*
This assumes that every class reachable from {@link ChangeInfo} has a non-private constructor
* with zero parameters and overrides the equals method.
*/
public final class ChangeInfoDiffer {
/**
* Returns the difference between two instances of {@link ChangeInfo}.
*
*
The {@link ChangeInfoDifference} returned has the following properties:
*
*
Unrepeated fields are present in the difference returned when they differ between {@code
* oldChangeInfo} and {@code newChangeInfo}. When there's an unrepeated field that's not a {@link
* String}, primitive, or enum, its fields are only returned when they differ.
*
*
Entries in {@link Map} fields are returned when a key is present in {@code newChangeInfo}
* and not {@code oldChangeInfo}. If a key is present in both, the diff of the value is returned.
*
*
{@link Collection} fields in {@link ChangeInfoDifference#added()} contain only items found
* in {@code newChangeInfo} and not {@code oldChangeInfo}.
*
*
{@link Collection} fields in {@link ChangeInfoDifference#removed()} contain only items found
* in {@code oldChangeInfo} and not {@code newChangeInfo}.
*
* @param oldChangeInfo the previous {@link ChangeInfo} to diff against {@code newChangeInfo}
* @param newChangeInfo the {@link ChangeInfo} to diff against {@code oldChangeInfo}
* @return the difference between the given {@link ChangeInfo}s
*/
public static ChangeInfoDifference getDifference(
ChangeInfo oldChangeInfo, ChangeInfo newChangeInfo) {
return ChangeInfoDifference.create(
/* added= */ getAdded(oldChangeInfo, newChangeInfo),
/* removed= */ getAdded(newChangeInfo, oldChangeInfo));
}
@SuppressWarnings("unchecked") // reflection is used to construct instances of T
private static T getAdded(T oldValue, T newValue) {
if (newValue instanceof Collection) {
List result = getAddedForCollection((Collection) oldValue, (Collection) newValue);
return (T) result;
}
if (newValue instanceof Map) {
Map result = getAddedForMap((Map) oldValue, (Map) newValue);
return (T) result;
}
T toPopulate = (T) construct(newValue.getClass());
if (toPopulate == null) {
return null;
}
for (Field field : newValue.getClass().getDeclaredFields()) {
if (java.lang.reflect.Modifier.isStatic(field.getModifiers())) {
continue;
}
Object newFieldObj = get(field, newValue);
if (oldValue == null || newFieldObj == null) {
set(field, toPopulate, newFieldObj);
continue;
}
Object oldFieldObj = get(field, oldValue);
if (newFieldObj.equals(oldFieldObj)) {
continue;
}
if (isSimple(field.getType()) || oldFieldObj == null) {
set(field, toPopulate, newFieldObj);
} else if (newFieldObj instanceof Collection || newFieldObj instanceof Map) {
set(field, toPopulate, getAdded(oldFieldObj, newFieldObj));
} else {
// Recurse to set all fields in the non-primitive object.
set(field, toPopulate, getAdded(oldFieldObj, newFieldObj));
}
}
return toPopulate;
}
@VisibleForTesting
static boolean isSimple(Class c) {
return c.isPrimitive()
|| c.isEnum()
|| String.class.isAssignableFrom(c)
|| Number.class.isAssignableFrom(c)
|| Boolean.class.isAssignableFrom(c)
|| Timestamp.class.isAssignableFrom(c);
}
@VisibleForTesting
static Object construct(Class c) {
// Only use constructors without parameters because we can't determine what values to pass.
return stream(c.getDeclaredConstructors())
.filter(constructor -> constructor.getParameterCount() == 0)
.findAny()
.map(ChangeInfoDiffer::construct)
.orElseThrow(
() ->
new IllegalStateException("Class " + c + " must have a zero argument constructor"));
}
private static Object construct(Constructor constructor) {
try {
return constructor.newInstance();
} catch (ReflectiveOperationException e) {
throw new IllegalStateException("Failed to construct class " + constructor.getName(), e);
}
}
/** @return {@code null} if nothing has been added to {@code oldCollection} */
private static ImmutableList getAddedForCollection(
Collection oldCollection, Collection newCollection) {
ImmutableList notInOldCollection = getAdditions(oldCollection, newCollection);
return notInOldCollection.isEmpty() ? null : notInOldCollection;
}
private static ImmutableList