org.openrewrite.Repeat Maven / Gradle / Ivy
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/*
* Copyright 2024 the original author or authors.
*
* 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
*
* https://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 org.openrewrite;
import org.jspecify.annotations.Nullable;
public class Repeat {
/**
* Returns a new visitor which runs the supplied visitor in a loop until no more changes are made, or a maximum
* of 3 cycles is reached.
* Convenient when a visitor is designed to recursively apply itself to a tree to achieve its desired result.
* Stops early if the visitor ceases to make changes to the tree before the maximum number of cycles is reached.
*/
public static TreeVisitor repeatUntilStable(TreeVisitor v) {
return repeatUntilStable(v, 3);
}
/**
* Returns a new visitor which runs the supplied visitor in a loop until no more changes are made, or the maximum
* number of cycles is reached.
* Convenient when a visitor is designed to recursively apply itself to a tree to achieve its desired result.
* Stops early if the visitor ceases to make changes to the tree before the maximum number of cycles is reached.
*/
public static TreeVisitor repeatUntilStable(TreeVisitor v, int maxCycles) {
return new TreeVisitor() {
@Override
public @Nullable Tree visit(@Nullable Tree tree, ExecutionContext ctx) {
if (tree instanceof SourceFile && !v.isAcceptable((SourceFile) tree, ctx)) {
return tree;
}
if (tree != null && !(tree instanceof SourceFile) && getCursor().isRoot()) {
throw new IllegalArgumentException(
String.format(
"Repeat visitor called on a non-source file tree without a cursor pointing to the root of the tree. " +
"Passed tree type: `%s`. " +
"This is likely a bug in the calling code. Use a `visit` method that accepts a cursor instead.",
tree.getClass().getName()
));
}
Tree previous = tree;
Tree current = null;
for (int i = 0; i < maxCycles; i++) {
current = v.visit(previous, ctx);
if (current == previous) {
break;
}
previous = current;
}
return current;
}
@Override
public @Nullable Tree visit(@Nullable Tree tree, ExecutionContext ctx, Cursor parent) {
if (tree instanceof SourceFile && !v.isAcceptable((SourceFile) tree, ctx)) {
return tree;
}
Tree previous = tree;
Tree current = null;
for (int i = 0; i < maxCycles; i++) {
current = v.visit(previous, ctx, parent);
if (current == previous) {
break;
}
previous = current;
}
return current;
}
};
}
}