Handle empty locations from patterns

Update `StandardConfigDataLocationResolver` to deal with patterns when
resolving empty directories. This update also fixes the handling of
mandatory pattern locations which would previously throw an exception.

The error message returned when a location with a pattern does not
contain any subdirectories has also been improved.

Fixes gh-26468
Fixes gh-26577
Fixes gh-26415

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/StandardConfigDataLocationResolver.java

@@ -18,6 +18,7 @@ package org.springframework.boot.context.config;
 
 import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Deque;
@@ -26,6 +27,7 @@ import java.util.List;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
 
@@ -243,19 +245,33 @@ public class StandardConfigDataLocationResolver
 			Set<StandardConfigDataReference> references) {
 		Set<StandardConfigDataResource> empty = new LinkedHashSet<>();
 		for (StandardConfigDataReference reference : references) {
-			if (reference.isMandatoryDirectory()) {
-				Resource resource = this.resourceLoader.getResource(reference.getDirectory());
-				if (resource instanceof ClassPathResource) {
-					continue;
-				}
-				StandardConfigDataResource configDataResource = new StandardConfigDataResource(reference, resource);
-				ConfigDataResourceNotFoundException.throwIfDoesNotExist(configDataResource, resource);
-				empty.add(new StandardConfigDataResource(reference, resource, true));
-			}
+			empty.addAll(resolveEmptyDirectories(reference));
 		}
 		return empty;
 	}
 
+	private Set<StandardConfigDataResource> resolveEmptyDirectories(StandardConfigDataReference reference) {
+		if (!this.resourceLoader.isPattern(reference.getResourceLocation())) {
+			return resolveNonPatternEmptyDirectories(reference);
+		}
+		return resolvePatternEmptyDirectories(reference);
+	}
+
+	private Set<StandardConfigDataResource> resolveNonPatternEmptyDirectories(StandardConfigDataReference reference) {
+		Resource resource = this.resourceLoader.getResource(reference.getDirectory());
+		return (resource instanceof ClassPathResource || !resource.exists()) ? Collections.emptySet()
+				: Collections.singleton(new StandardConfigDataResource(reference, resource, true));
+	}
+
+	private Set<StandardConfigDataResource> resolvePatternEmptyDirectories(StandardConfigDataReference reference) {
+		Resource[] resources = this.resourceLoader.getResources(reference.getDirectory(), ResourceType.DIRECTORY);
+		Assert.state(resources.length > 0,
+				"No subdirectories found for mandatory directory location '" + reference.getDirectory() + "'.");
+		return Arrays.stream(resources).filter(Resource::exists)
+				.map((resource) -> new StandardConfigDataResource(reference, resource, true))
+				.collect(Collectors.toCollection(LinkedHashSet::new));
+	}
+
 	private List<StandardConfigDataResource> resolve(StandardConfigDataReference reference) {
 		if (!this.resourceLoader.isPattern(reference.getResourceLocation())) {
 			return resolveNonPattern(reference);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessorIntegrationTests.java

@@ -547,7 +547,7 @@ class ConfigDataEnvironmentPostProcessorIntegrationTests {
 	@Test
 	void runWhenConfigLocationHasNonOptionalMissingFileDirectoryThrowsResourceNotFoundException() {
 		File location = new File(this.temp, "application.unknown");
-		assertThatExceptionOfType(ConfigDataResourceNotFoundException.class).isThrownBy(() -> this.application
+		assertThatExceptionOfType(ConfigDataLocationNotFoundException.class).isThrownBy(() -> this.application
 				.run("--spring.config.location=" + StringUtils.cleanPath(location.getAbsolutePath()) + "/"));
 	}
 
@@ -566,6 +566,12 @@ class ConfigDataEnvironmentPostProcessorIntegrationTests {
 				.run("--spring.config.location=" + StringUtils.cleanPath(location.getAbsolutePath()) + "/"));
 	}
 
+	@Test
+	void runWhenConfigLocationHasMandatoryDirectoryThatDoesntExistThrowsException() {
+		assertThatExceptionOfType(ConfigDataLocationNotFoundException.class).isThrownBy(
+				() -> this.application.run("--spring.config.location=" + StringUtils.cleanPath("invalid/")));
+	}
+
 	@Test
 	void runWhenConfigLocationHasNonOptionalEmptyFileDoesNotThrowException() throws IOException {
 		File location = new File(this.temp, "application.properties");
@@ -686,13 +692,32 @@ class ConfigDataEnvironmentPostProcessorIntegrationTests {
 	@Test
 	void runWhenHasWildcardLocationLoadsFromAllMatchingLocations() {
 		ConfigurableApplicationContext context = this.application.run(
-				"--spring.config.location=optional:file:src/test/resources/config/*/",
-				"--spring.config.name=testproperties");
+				"--spring.config.location=file:src/test/resources/config/*/", "--spring.config.name=testproperties");
 		ConfigurableEnvironment environment = context.getEnvironment();
 		assertThat(environment.getProperty("first.property")).isEqualTo("apple");
 		assertThat(environment.getProperty("second.property")).isEqualTo("ball");
 	}
 
+	@Test
+	void runWhenMandatoryWildcardLocationHasEmptyFileDirectory() {
+		assertThatNoException()
+				.isThrownBy(() -> this.application.run("--spring.config.location=file:src/test/resources/config/*/"));
+	}
+
+	@Test
+	void runWhenMandatoryWildcardLocationHasNoSubdirectories() {
+		assertThatIllegalStateException().isThrownBy(
+				() -> this.application.run("--spring.config.location=file:src/test/resources/config/0-empty/*/"))
+				.withMessage(
+						"No subdirectories found for mandatory directory location 'file:src/test/resources/config/0-empty/*/'.");
+	}
+
+	@Test
+	void runWhenHasMandatoryWildcardLocationThatDoesNotExist() {
+		assertThatExceptionOfType(ConfigDataLocationNotFoundException.class)
+				.isThrownBy(() -> this.application.run("--spring.config.location=file:invalid/*/"));
+	}
+
 	@Test // gh-24990
 	void runWhenHasProfileSpecificFileWithActiveOnProfileProperty() {
 		ConfigurableApplicationContext context = this.application