Expose AddOrUpdateChild as a recipe using XPath

rewrite-xml/src/main/java/org/openrewrite/xml/AddOrUpdateChildTag.java

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+/*
+ * Copyright 2022 the original author or authors.
+ * <p>
+ * 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
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.xml;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.intellij.lang.annotations.Language;
+import org.openrewrite.*;
+import org.openrewrite.xml.tree.Xml;
+
+@Value
+@AllArgsConstructor
+@EqualsAndHashCode(callSuper = false)
+public class AddOrUpdateChildTag extends Recipe {
+
+    @Option(displayName = "Parent XPath",
+            description = "XPath identifying the parent to which a child tag must be added",
+            example = "/project//plugin//configuration")
+    @Language("xpath")
+    String parentXPath;
+
+    @Option(displayName = "New child tag",
+            description = "The XML of the new child to add or update on the parent tag.",
+            example = "<skip>true</skip>")
+    @Language("xml")
+    String newChildTag;
+
+    @Override
+    public String getDisplayName() {
+        return "Add or update child tag";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Adds or updates a child element below the parent(s) matching the provided `parentXPath` expression. " +
+               "If a child with the same name exists, it will be replaced, otherwise a new child will be added. " +
+               "This ensures idempotent behaviour.";
+    }
+
+    @Override
+    public Validated<Object> validate() {
+        Validated<Object> validated = super.validate()
+                .and(Validated.notBlank("parentXPath", parentXPath))
+                .and(Validated.notBlank("newChildTag", newChildTag));
+        try {
+            Xml.Tag.build(newChildTag);
+        } catch (Exception e) {
+            validated = validated.and(Validated.invalid("newChildTag", newChildTag, "Invalid XML for child tag", e));
+        }
+        return validated;
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new XmlVisitor<ExecutionContext>() {
+            private final XPathMatcher xPathMatcher = new XPathMatcher(parentXPath);
+
+            @Override
+            public Xml visitTag(Xml.Tag tag, ExecutionContext ctx) {
+                if (xPathMatcher.matches(getCursor())) {
+                    Xml.Tag newChild = Xml.Tag.build(newChildTag);
+                    return AddOrUpdateChild.addOrUpdateChild(tag, newChild, getCursor().getParentOrThrow());
+                }
+                return super.visitTag(tag, ctx);
+            }
+        };
+    }
+}