Introduce ResourcePatternHint#toRegex

This change is done for several reasons:
 - Move the logic where it is documented.
 - Test it with ResourcePatternHintTests.
 - Allow RuntimeHintsPredicates to leverage this logic.

Closes gh-28620

spring-core/src/main/java/org/springframework/aot/hint/ResourcePatternHint.java

@@ -16,7 +16,10 @@
 
 package org.springframework.aot.hint;
 
+import java.util.Arrays;
 import java.util.Objects;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import org.springframework.lang.Nullable;
 
@@ -58,12 +61,26 @@ public final class ResourcePatternHint implements ConditionalHint {
 
 	/**
 	 * Return the pattern to use for identifying the resources to match.
-	 * @return the patterns
+	 * @return the pattern
 	 */
 	public String getPattern() {
 		return this.pattern;
 	}
 
+	/**
+	 * Return the regex {@link Pattern} to use for identifying the resources to match.
+	 * @return the regex pattern
+	 */
+	public Pattern toRegex() {
+		String prefix = (this.pattern.startsWith("*") ? ".*" : "");
+		String suffix = (this.pattern.endsWith("*") ? ".*" : "");
+		String regex = Arrays.stream(this.pattern.split("\\*"))
+				.filter(s -> !s.isEmpty())
+				.map(Pattern::quote)
+				.collect(Collectors.joining(".*", prefix, suffix));
+		return Pattern.compile(regex);
+	}
+
 	@Nullable
 	@Override
 	public TypeReference getReachableType() {

spring-core/src/main/java/org/springframework/aot/nativex/ResourceHintsWriter.java

@@ -16,13 +16,10 @@
 
 package org.springframework.aot.nativex;
 
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.regex.Pattern;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import org.springframework.aot.hint.ConditionalHint;
@@ -77,19 +74,10 @@ class ResourceHintsWriter {
 	private Map<String, Object> toAttributes(ResourcePatternHint hint) {
 		Map<String, Object> attributes = new LinkedHashMap<>();
 		handleCondition(attributes, hint);
-		attributes.put("pattern", patternToRegexp(hint.getPattern()));
+		attributes.put("pattern", hint.toRegex().toString());
 		return attributes;
 	}
 
-	private String patternToRegexp(String pattern) {
-		String prefix = (pattern.startsWith("*") ? ".*" : "");
-		String suffix = (pattern.endsWith("*") ? ".*" : "");
-		return Arrays.stream(pattern.split("\\*"))
-				.filter(s -> !s.isEmpty())
-				.map(Pattern::quote)
-				.collect(Collectors.joining(".*", prefix, suffix));
-	}
-
 	private void addIfNotEmpty(Map<String, Object> attributes, String name, @Nullable Object value) {
 		if (value instanceof Collection<?> collection) {
 			if (!collection.isEmpty()) {

spring-core/src/test/java/org/springframework/aot/hint/ResourcePatternHintTests.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2002-2022 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.springframework.aot.hint;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ResourcePatternHint}.
+ *
+ * @author Sebastien Deleuze
+ */
+public class ResourcePatternHintTests {
+
+	@Test
+	void fileAtRoot() {
+		ResourcePatternHint hint = new ResourcePatternHint("file.properties", null);
+		assertThat(hint.toRegex().asMatchPredicate())
+				.accepts("file.properties")
+				.rejects("com/example/file.properties", "file.prop", "another-file.properties");
+	}
+
+	@Test
+	void fileInDirectory() {
+		ResourcePatternHint hint = new ResourcePatternHint("com/example/file.properties", null);
+		assertThat(hint.toRegex().asMatchPredicate())
+				.accepts("com/example/file.properties")
+				.rejects("file.properties", "com/file.properties", "com/example/another-file.properties");
+	}
+
+	@Test
+	void extension() {
+		ResourcePatternHint hint = new ResourcePatternHint("*.properties", null);
+		assertThat(hint.toRegex().asMatchPredicate())
+				.accepts("file.properties", "com/example/file.properties")
+				.rejects("file.prop", "com/example/file.prop");
+	}
+
+	@Test
+	void extensionInDirectoryAtAnyDepth() {
+		ResourcePatternHint hint = new ResourcePatternHint("com/example/*.properties", null);
+		assertThat(hint.toRegex().asMatchPredicate())
+				.accepts("com/example/file.properties", "com/example/another/file.properties")
+				.rejects("file.properties", "com/file.properties");
+	}
+
+	@Test
+	void anyFileInDirectoryAtAnyDepth() {
+		ResourcePatternHint hint = new ResourcePatternHint("com/example/*", null);
+		assertThat(hint.toRegex().asMatchPredicate())
+				.accepts("com/example/file.properties", "com/example/another/file.properties", "com/example/another")
+				.rejects("file.properties", "com/file.properties");
+	}
+}