software.amazon.smithy.diff.evaluators.ChangedDefault Maven / Gradle / Ivy

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This module detects differences between two Smithy models, identifying changes that are safe and changes that are backward incompatible.
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/*
 * Copyright 2022 Amazon.com, Inc. or its affiliates. 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.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 software.amazon.smithy.diff.evaluators;

import java.util.ArrayList;
import java.util.List;
import software.amazon.smithy.diff.ChangedShape;
import software.amazon.smithy.diff.Differences;
import software.amazon.smithy.model.Model;
import software.amazon.smithy.model.knowledge.NullableIndex;
import software.amazon.smithy.model.node.Node;
import software.amazon.smithy.model.shapes.MemberShape;
import software.amazon.smithy.model.shapes.Shape;
import software.amazon.smithy.model.shapes.ShapeType;
import software.amazon.smithy.model.traits.AddedDefaultTrait;
import software.amazon.smithy.model.traits.DefaultTrait;
import software.amazon.smithy.model.validation.ValidationEvent;
import software.amazon.smithy.utils.SmithyInternalApi;

@SmithyInternalApi
public final class ChangedDefault extends AbstractDiffEvaluator {
    @Override
    public List evaluate(Differences differences) {
        List events = new ArrayList<>();

        // Find changes in the DefaultTrait.
        differences.changedShapes().forEach(change -> {
            change.getTraitDifferences().forEach((traitId, pair) -> {
                if (traitId.equals(DefaultTrait.ID)) {
                    if ((pair.left == null || pair.left instanceof DefaultTrait)
                            && (pair.right == null || pair.right instanceof DefaultTrait)) {
                        validateChange(events, differences.getNewModel(), change,
                                       (DefaultTrait) pair.left, (DefaultTrait) pair.right);
                    }
                }
            });
        });

        return events;
    }

    private void validateChange(
            List events,
            Model model,
            ChangedShape change,
            DefaultTrait oldTrait,
            DefaultTrait newTrait
    ) {
        if (newTrait == null) {
            if (!isInconsequentialRemovalOfDefaultTrait(model, oldTrait, change.getNewShape())) {
                events.add(error(change.getNewShape(),
                                 "@default trait was removed. This will break previously generated code."));
            }
        } else if (oldTrait == null) {
            if (change.getNewShape().getType() != ShapeType.MEMBER) {
                events.add(error(change.getNewShape(), newTrait,
                                 "Adding the @default trait to a root-level shape will break previously generated "
                                 + "code. Added @default: " + Node.printJson(newTrait.toNode())));
            } else if (!change.getNewShape().hasTrait(AddedDefaultTrait.class)) {
                if (!newTrait.toNode().isNullNode()) {
                    events.add(error(change.getNewShape(), newTrait,
                                     "Adding the @default trait to a member without also adding the @addedDefault "
                                     + "trait will break previously generated code. Added @default: "
                                     + Node.printJson(newTrait.toNode())));
                }
            }
        } else if (!oldTrait.toNode().equals(newTrait.toNode())) {
            if (change.getNewShape().isMemberShape()) {
                evaluateChangedTrait(model, change.getNewShape().asMemberShape().get(), oldTrait, newTrait, events);
            } else {
                events.add(error(change.getNewShape(), newTrait,
                                 "Changing the @default value of a root-level shape will break previously generated "
                                 + "code. Old value: " + Node.printJson(oldTrait.toNode())
                                 + ". New value: " + Node.printJson(newTrait.toNode())));
            }
        }
    }

    private boolean isInconsequentialRemovalOfDefaultTrait(Model model, DefaultTrait trait, Shape removedFrom) {
        // Removing a default of null if the target is nullable is not an issue.
        return removedFrom.asMemberShape()
                .map(member -> {
                    if (trait.toNode().isNullNode()) {
                        // If the target has no defined default, then removing a default(null) trait is fine.
                        Node targetDefault = model.expectShape(member.getTarget())
                                .getTrait(DefaultTrait.class)
                                .map(DefaultTrait::toNode)
                                .orElse(Node.nullNode()); // If no default, then assume target has a default of null.
                        return targetDefault.isNullNode();
                    } else {
                        // Removing a non-null trait is always an issue.
                        return false;
                    }
                })
                .orElse(false);
    }

    private void evaluateChangedTrait(Model model, MemberShape member, DefaultTrait oldTrait,
            DefaultTrait newTrait, List events) {
        Shape target = model.expectShape(member.getTarget());
        Node oldValue = oldTrait.toNode();
        Node newValue = newTrait.toNode();
        boolean oldZeroValue = NullableIndex.isDefaultZeroValueOfTypeInV1(oldValue, target.getType());
        boolean newZeroValue = NullableIndex.isDefaultZeroValueOfTypeInV1(newValue, target.getType());

        if (oldZeroValue == newZeroValue) {
            events.add(danger(member, newTrait, "Changing the @default value of a member is dangerous and could break "
                                                + "previously generated code or lead to subtle errors. Do this only "
                                                + "when strictly necessary. Old value: " + Node.printJson(oldValue)
                                                + ". New value: " + Node.printJson(newValue)));
        } else if (oldZeroValue) {
            events.add(error(member, newTrait, "The @default trait of this member changed from the zero value of the "
                                               + "target shape, `" + Node.printJson(oldValue) + "`, to a value that "
                                               + "is not the zero value, `" + Node.printJson(newValue) + "`. This "
                                               + "will break previously generated code."));
        } else {
            events.add(error(member, newTrait, "The @default trait of this member changed from something other than "
                                               + "the zero value of the target shape, `" + Node.printJson(oldValue)
                                               + "`, to the zero value, `" + Node.printJson(newValue) + "`. This "
                                               + "will break previously generated code."));
        }
    }
}