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// Copyright (C) 2020 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
// Copyright (C) 2020 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.truth;
import com.google.common.base.Function;
import com.google.common.truth.Correspondence;
import java.util.Optional;
/** Utility class for constructing null aware {@link Correspondence}s. */
public class NullAwareCorrespondence {
/**
* Constructs a {@link Correspondence} that compares elements by transforming the actual elements
* using the given function and testing for equality with the expected elements.
*
* <p>If the actual element is null, it will correspond to a null expected element. This is
* different to {@link Correspondence#transforming(Function, String)} which would invoke the
* function with a {@code null} argument, requiring the function being able to handle {@code
* null}.
*
* @param actualTransform a {@link Function} taking an actual value and returning a new value
* which will be compared with an expected value to determine whether they correspond
* @param description should fill the gap in a failure message of the form {@code "not true that
* <some actual element> is an element that <description> <some expected element>"}, e.g.
* {@code "has an ID of"}
*/
public static <A, E> Correspondence<A, E> transforming(
Function<A, ? extends E> actualTransform, String description) {
return Correspondence.transforming(
actualValue -> Optional.ofNullable(actualValue).map(actualTransform).orElse(null),
description);
}
/**
* Constructs a {@link Correspondence} that compares elements by transforming the actual elements
* using the given function and testing for equality with the expected elements.
*
* <p>If the actual element is null, it will correspond to a null expected element. This is
* different to {@link Correspondence#transforming(Function, Function, String)} which would invoke
* the function with a {@code null} argument, requiring the function being able to handle {@code
* null}.
*
* <p>If the expected element is null, it will correspond to a new null expected element. This is
* different to {@link Correspondence#transforming(Function, Function, String)} which would invoke
* the function with a {@code null} argument, requiring the function being able to handle {@code
* null}.
*
* @param actualTransform a {@link Function} taking an actual value and returning a new value
* which will be compared with an expected value to determine whether they correspond
* @param expectedTransform a {@link Function} taking an expected value and returning a new value
* which will be compared with a transformed actual value
* @param description should fill the gap in a failure message of the form {@code "not true that
* <some actual element> is an element that <description> <some expected element>"}, e.g.
* {@code "has an ID of"}
*/
public static <A, E> Correspondence<A, E> transforming(
Function<A, ? extends E> actualTransform,
Function<E, ?> expectedTransform,
String description) {
return Correspondence.transforming(
actualValue -> Optional.ofNullable(actualValue).map(actualTransform).orElse(null),
expectedValue -> Optional.ofNullable(expectedValue).map(expectedTransform).orElse(null),
description);
}
/**
* Private constructor to prevent instantiation of this class.
*
* <p>This class contains only static method and hence never needs to be instantiated.
*/
private NullAwareCorrespondence() {}
}