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[MNG-8281] Interpolator service
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‎api/maven-api-core/src/main/java/org/apache/maven/api/services/Interpolator.java

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.maven.api.services;
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import java.util.Collection;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Optional;
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import java.util.function.BiFunction;
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import java.util.function.Function;
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import org.apache.maven.api.Service;
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import org.apache.maven.api.annotations.Experimental;
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import org.apache.maven.api.annotations.Nonnull;
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import org.apache.maven.api.annotations.Nullable;
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/**
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* The Interpolator service provides methods for variable substitution in strings and maps.
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* It allows for the replacement of placeholders (e.g., ${variable}) with their corresponding values.
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*
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* @since 4.0.0
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*/
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@Experimental
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public interface Interpolator extends Service {
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/**
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* Interpolates the values in the given map using the provided callback function.
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* This method defaults to setting empty strings for unresolved placeholders.
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*
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* @param properties The map containing key-value pairs to be interpolated.
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* @param callback The function to resolve variable values not found in the map.
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*/
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default void interpolate(@Nonnull Map<String, String> properties, @Nullable Function<String, String> callback) {
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interpolate(properties, callback, null, true);
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}
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/**
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* Interpolates the values in the given map using the provided callback function.
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*
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* @param map The map containing key-value pairs to be interpolated.
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* @param callback The function to resolve variable values not found in the map.
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* @param defaultsToEmpty If true, unresolved placeholders are replaced with empty strings. If false, they are left unchanged.
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*/
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default void interpolate(
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@Nonnull Map<String, String> map, @Nullable Function<String, String> callback, boolean defaultsToEmpty) {
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interpolate(map, callback, null, defaultsToEmpty);
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}
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/**
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* Interpolates the values in the given map using the provided callback function.
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*
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* @param map The map containing key-value pairs to be interpolated.
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* @param callback The function to resolve variable values not found in the map.
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* @param defaultsToEmpty If true, unresolved placeholders are replaced with empty strings. If false, they are left unchanged.
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*/
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void interpolate(
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@Nonnull Map<String, String> map,
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@Nullable Function<String, String> callback,
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@Nullable BiFunction<String, String, String> postprocessor,
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boolean defaultsToEmpty);
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/**
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* Interpolates a single string value using the provided callback function.
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* This method defaults to not replacing unresolved placeholders.
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*
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* @param val The string to be interpolated.
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* @param callback The function to resolve variable values.
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* @return The interpolated string, or null if the input was null.
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*/
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@Nullable
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default String interpolate(@Nullable String val, @Nullable Function<String, String> callback) {
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return interpolate(val, callback, false);
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}
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/**
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* Interpolates a single string value using the provided callback function.
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*
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* @param val The string to be interpolated.
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* @param callback The function to resolve variable values.
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* @param defaultsToEmpty If true, unresolved placeholders are replaced with empty strings.
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* @return The interpolated string, or null if the input was null.
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*/
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@Nullable
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default String interpolate(
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@Nullable String val, @Nullable Function<String, String> callback, boolean defaultsToEmpty) {
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return interpolate(val, callback, null, defaultsToEmpty);
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}
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/**
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* Interpolates a single string value using the provided callback function.
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*
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* @param val The string to be interpolated.
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* @param callback The function to resolve variable values.
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* @param defaultsToEmpty If true, unresolved placeholders are replaced with empty strings.
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* @return The interpolated string, or null if the input was null.
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*/
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@Nullable
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String interpolate(
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@Nullable String val,
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@Nullable Function<String, String> callback,
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@Nullable BiFunction<String, String, String> postprocessor,
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boolean defaultsToEmpty);
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/**
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* Creates a composite function from a collection of functions.
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*
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* @param functions A collection of functions, each taking a String as input and returning a String.
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* @return A function that applies each function in the collection in order until a non-null result is found.
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* If all functions return null, the composite function returns null.
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*
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* @implNote This implementation uses Java streams to process the collection of functions.
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* It applies each function to the input string and returns the first non-null result.
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* If all functions return null, it returns null.
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* The returned function is not thread-safe if the input collection is modified after this method is called.
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*
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* @throws NullPointerException if the input collection is null or contains null elements.
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*/
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static Function<String, String> chain(Collection<? extends Function<String, String>> functions) {
135+
return s -> {
136+
for (Function<String, String> function : functions) {
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String v = function.apply(s);
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if (v != null) {
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return v;
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}
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}
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return null;
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};
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}
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/**
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* Memoizes a given function that takes a String input and produces a String output.
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* This method creates a new function that caches the results of the original function,
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* improving performance for repeated calls with the same input.
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*
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* @param callback The original function to be memoized. It takes a String as input and returns a String.
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* @return A new Function<String, String> that caches the results of the original function.
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* If the original function returns null for a given input, null will be cached and returned for subsequent calls with the same input.
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*
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* @implNote This implementation uses a HashMap to store the cached results.
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* The cache keys are the input Strings, and the values are Optional<String> to handle null results.
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* The returned function is thread-safe for concurrent access.
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*
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* @see Function
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* @see Optional
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* @see HashMap#computeIfAbsent(Object, Function)
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*/
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static Function<String, String> memoize(Function<String, String> callback) {
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Map<String, Optional<String>> cache = new HashMap<>();
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return s -> cache.computeIfAbsent(s, v -> Optional.ofNullable(callback.apply(v))).orElse(null);
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}
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}

‎api/maven-api-core/src/main/java/org/apache/maven/api/services/InterpolatorException.java

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
3+
* or more contributor license agreements. See the NOTICE file
4+
* distributed with this work for additional information
5+
* regarding copyright ownership. The ASF licenses this file
6+
* to you under the Apache License, Version 2.0 (the
7+
* "License"); you may not use this file except in compliance
8+
* with the License. You may obtain a copy of the License at
9+
*
10+
* http://www.apache.org/licenses/LICENSE-2.0
11+
*
12+
* Unless required by applicable law or agreed to in writing,
13+
* software distributed under the License is distributed on an
14+
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15+
* KIND, either express or implied. See the License for the
16+
* specific language governing permissions and limitations
17+
* under the License.
18+
*/
19+
package org.apache.maven.api.services;
20+
21+
import java.io.Serial;
22+
23+
import org.apache.maven.api.annotations.Experimental;
24+
25+
/**
26+
* Exception thrown by {@link Interpolator} implementations when an error occurs during interpolation.
27+
* This can include syntax errors in variable placeholders or recursive variable references.
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*
29+
* @since 4.0.0
30+
*/
31+
@Experimental
32+
public class InterpolatorException extends MavenException {
33+
34+
@Serial
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private static final long serialVersionUID = -1219149033636851813L;
36+
37+
/**
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* Constructs a new InterpolatorException with {@code null} as its
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* detail message. The cause is not initialized, and may subsequently be
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* initialized by a call to {@link #initCause}.
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*/
42+
public InterpolatorException() {}
43+
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/**
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* Constructs a new InterpolatorException with the specified detail message.
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* The cause is not initialized, and may subsequently be initialized by
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* a call to {@link #initCause}.
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*
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* @param message the detail message. The detail message is saved for
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* later retrieval by the {@link #getMessage()} method.
51+
*/
52+
public InterpolatorException(String message) {
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super(message);
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}
55+
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/**
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* Constructs a new InterpolatorException with the specified detail message and cause.
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*
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* <p>Note that the detail message associated with {@code cause} is <i>not</i>
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* automatically incorporated in this exception's detail message.</p>
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*
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* @param message the detail message (which is saved for later retrieval
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* by the {@link #getMessage()} method).
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* @param cause the cause (which is saved for later retrieval by the
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* {@link #getCause()} method). A {@code null} value is
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* permitted, and indicates that the cause is nonexistent or unknown.
67+
*/
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public InterpolatorException(String message, Throwable cause) {
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super(message, cause);
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}
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}

‎maven-api-impl/pom.xml

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@@ -91,10 +91,6 @@ under the License.
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<groupId>org.apache.maven</groupId>
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<artifactId>maven-xml-impl</artifactId>
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</dependency>
94-
<dependency>
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<groupId>org.codehaus.plexus</groupId>
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<artifactId>plexus-interpolation</artifactId>
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</dependency>
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<dependency>
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<groupId>com.fasterxml.woodstox</groupId>
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<artifactId>woodstox-core</artifactId>

‎maven-api-impl/src/main/java/org/apache/maven/api/services/model/ModelInterpolator.java

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@@ -20,6 +20,8 @@
2020

2121
import java.nio.file.Path;
2222

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import org.apache.maven.api.annotations.Nonnull;
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import org.apache.maven.api.annotations.Nullable;
2325
import org.apache.maven.api.model.Model;
2426
import org.apache.maven.api.services.ModelBuilderRequest;
2527
import org.apache.maven.api.services.ModelProblemCollector;
@@ -32,9 +34,7 @@
3234
public interface ModelInterpolator {
3335

3436
/**
35-
* Interpolates expressions in the specified model. Note that implementations are free to either interpolate the
36-
* provided model directly or to create a clone of the model and interpolate the clone. Callers should always use
37-
* the returned model and must not rely on the input model being updated.
37+
* Interpolates expressions in the specified model.
3838
*
3939
* @param model The model to interpolate, must not be {@code null}.
4040
* @param projectDir The project directory, may be {@code null} if the model does not belong to a local project but
@@ -44,5 +44,10 @@ public interface ModelInterpolator {
4444
* @return The interpolated model, never {@code null}.
4545
* @since 4.0.0
4646
*/
47-
Model interpolateModel(Model model, Path projectDir, ModelBuilderRequest request, ModelProblemCollector problems);
47+
@Nonnull
48+
Model interpolateModel(
49+
@Nonnull Model model,
50+
@Nullable Path projectDir,
51+
@Nonnull ModelBuilderRequest request,
52+
@Nonnull ModelProblemCollector problems);
4853
}

‎maven-api-impl/src/main/java/org/apache/maven/api/services/model/RootLocator.java

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@@ -42,7 +42,7 @@ public interface RootLocator extends Service {
4242
+ " attribute on the root project's model to identify it.";
4343

4444
@Nonnull
45-
default Path findMandatoryRoot(Path basedir) {
45+
default Path findMandatoryRoot(@Nullable Path basedir) {
4646
Path rootDirectory = findRoot(basedir);
4747
if (rootDirectory == null) {
4848
throw new IllegalStateException(getNoRootMessage());
@@ -51,7 +51,7 @@ default Path findMandatoryRoot(Path basedir) {
5151
}
5252

5353
@Nullable
54-
default Path findRoot(Path basedir) {
54+
default Path findRoot(@Nullable Path basedir) {
5555
Path rootDirectory = basedir;
5656
while (rootDirectory != null && !isRootDirectory(rootDirectory)) {
5757
rootDirectory = rootDirectory.getParent();

‎maven-api-impl/src/main/java/org/apache/maven/internal/impl/DefaultSettingsBuilder.java

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2828
import java.nio.file.Paths;
2929
import java.util.ArrayList;
3030
import java.util.List;
31+
import java.util.Map;
32+
import java.util.function.Function;
3133

34+
import org.apache.maven.api.di.Inject;
3235
import org.apache.maven.api.di.Named;
3336
import org.apache.maven.api.services.BuilderProblem;
37+
import org.apache.maven.api.services.Interpolator;
3438
import org.apache.maven.api.services.SettingsBuilder;
3539
import org.apache.maven.api.services.SettingsBuilderException;
3640
import org.apache.maven.api.services.SettingsBuilderRequest;
@@ -44,12 +48,9 @@
4448
import org.apache.maven.api.settings.RepositoryPolicy;
4549
import org.apache.maven.api.settings.Server;
4650
import org.apache.maven.api.settings.Settings;
51+
import org.apache.maven.internal.impl.model.DefaultInterpolator;
4752
import org.apache.maven.settings.v4.SettingsMerger;
4853
import org.apache.maven.settings.v4.SettingsTransformer;
49-
import org.codehaus.plexus.interpolation.EnvarBasedValueSource;
50-
import org.codehaus.plexus.interpolation.InterpolationException;
51-
import org.codehaus.plexus.interpolation.MapBasedValueSource;
52-
import org.codehaus.plexus.interpolation.RegexBasedInterpolator;
5354

5455
/**
5556
* Builds the effective settings from a user settings file and/or a global settings file.
@@ -62,6 +63,17 @@ public class DefaultSettingsBuilder implements SettingsBuilder {
6263

6364
private final SettingsMerger settingsMerger = new SettingsMerger();
6465

66+
private final Interpolator interpolator;
67+
68+
public DefaultSettingsBuilder() {
69+
this(new DefaultInterpolator());
70+
}
71+
72+
@Inject
73+
public DefaultSettingsBuilder(Interpolator interpolator) {
74+
this.interpolator = interpolator;
75+
}
76+
6577
@Override
6678
public SettingsBuilderResult build(SettingsBuilderRequest request) throws SettingsBuilderException {
6779
List<BuilderProblem> problems = new ArrayList<>();
@@ -213,39 +225,10 @@ private Settings readSettings(
213225
}
214226

215227
private Settings interpolate(Settings settings, SettingsBuilderRequest request, List<BuilderProblem> problems) {
216-
217-
RegexBasedInterpolator interpolator = new RegexBasedInterpolator();
218-
219-
interpolator.addValueSource(new MapBasedValueSource(request.getSession().getUserProperties()));
220-
221-
interpolator.addValueSource(new MapBasedValueSource(request.getSession().getSystemProperties()));
222-
223-
try {
224-
interpolator.addValueSource(new EnvarBasedValueSource());
225-
} catch (IOException e) {
226-
problems.add(new DefaultBuilderProblem(
227-
null,
228-
-1,
229-
-1,
230-
e,
231-
"Failed to use environment variables for interpolation: " + e.getMessage(),
232-
BuilderProblem.Severity.WARNING));
233-
}
234-
235-
return new SettingsTransformer(value -> {
236-
try {
237-
return value != null ? interpolator.interpolate(value) : null;
238-
} catch (InterpolationException e) {
239-
problems.add(new DefaultBuilderProblem(
240-
null,
241-
-1,
242-
-1,
243-
e,
244-
"Failed to interpolate settings: " + e.getMessage(),
245-
BuilderProblem.Severity.WARNING));
246-
return value;
247-
}
248-
})
228+
Map<String, String> userProperties = request.getSession().getUserProperties();
229+
Map<String, String> systemProperties = request.getSession().getSystemProperties();
230+
Function<String, String> src = Interpolator.chain(List.of(userProperties::get, systemProperties::get));
231+
return new SettingsTransformer(value -> value != null ? interpolator.interpolate(value, src) : null)
249232
.visit(settings);
250233
}
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