Fix non-optional classpath location checking

Allow directory locations that exist but do not contribute properties
to be specified without an `optional:` prefix. This commit fixes logic
introduced in commit 3dc03ac which didn't account for the fact that
a directory might contain only profile specific property files and that
profiles might not always be active.

Closes gh-24499

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

@@ -45,6 +45,11 @@ public final class ConfigData {
 
 	private final Set<Option> options;
 
+	/**
+	 * A {@link ConfigData} instance that contains no data.
+	 */
+	public static final ConfigData EMPTY = new ConfigData(Collections.emptySet());
+
 	/**
 	 * Create a new {@link ConfigData} instance.
 	 * @param propertySources the config data property sources in ascending priority

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

@@ -300,6 +300,15 @@ static ConfigDataEnvironmentContributor ofUnboundImport(ConfigDataLocation locat
 				configurationPropertySource, null, ignoreImports, null);
 	}
 
+	/**
+	 * Factory method to create an {@link Kind#EMPTY_LOCATION empty location} contributor.
+	 * @param location the location of this contributor
+	 * @return a new {@link ConfigDataEnvironmentContributor} instance
+	 */
+	static ConfigDataEnvironmentContributor ofEmptyLocation(ConfigDataLocation location) {
+		return new ConfigDataEnvironmentContributor(Kind.EMPTY_LOCATION, location, null, null, null, null, true, null);
+	}
+
 	/**
 	 * The various kinds of contributor.
 	 */
@@ -330,7 +339,12 @@ enum Kind {
 		 * A contributor with {@link ConfigData} imported from another contributor that
 		 * has been.
 		 */
-		BOUND_IMPORT;
+		BOUND_IMPORT,
+
+		/**
+		 * A valid location that contained noething to load.
+		 */
+		EMPTY_LOCATION;
 
 	}
 

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

@@ -161,10 +161,15 @@ private List<ConfigDataEnvironmentContributor> asContributors(
 			Map<ConfigDataResolutionResult, ConfigData> imported) {
 		List<ConfigDataEnvironmentContributor> contributors = new ArrayList<>(imported.size() * 5);
 		imported.forEach((resolutionResult, data) -> {
-			for (int i = data.getPropertySources().size() - 1; i >= 0; i--) {
-				ConfigDataLocation location = resolutionResult.getLocation();
-				ConfigDataResource resource = resolutionResult.getResource();
-				contributors.add(ConfigDataEnvironmentContributor.ofUnboundImport(location, resource, data, i));
+			ConfigDataLocation location = resolutionResult.getLocation();
+			ConfigDataResource resource = resolutionResult.getResource();
+			if (data.getPropertySources().isEmpty()) {
+				contributors.add(ConfigDataEnvironmentContributor.ofEmptyLocation(location));
+			}
+			else {
+				for (int i = data.getPropertySources().size() - 1; i >= 0; i--) {
+					contributors.add(ConfigDataEnvironmentContributor.ofUnboundImport(location, resource, data, i));
+				}
 			}
 		});
 		return Collections.unmodifiableList(contributors);

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

@@ -36,6 +36,9 @@ public class StandardConfigDataLoader implements ConfigDataLoader<StandardConfig
 	@Override
 	public ConfigData load(ConfigDataLoaderContext context, StandardConfigDataResource resource)
 			throws IOException, ConfigDataNotFoundException {
+		if (resource.isEmptyDirectory()) {
+			return ConfigData.EMPTY;
+		}
 		ConfigDataResourceNotFoundException.throwIfDoesNotExist(resource, resource.getResource());
 		StandardConfigDataReference reference = resource.getReference();
 		Resource originTrackedResource = OriginTrackedResource.of(resource.getResource(),

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

@@ -17,6 +17,7 @@
 package org.springframework.boot.context.config;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -220,25 +221,26 @@ private List<StandardConfigDataResource> resolve(Set<StandardConfigDataReference
 			resolved.addAll(resolve(reference));
 		}
 		if (resolved.isEmpty()) {
-			assertNonOptionalDirectories(references);
+			resolved.addAll(resolveEmptyDirectories(references));
 		}
 		return resolved;
 	}
 
-	private void assertNonOptionalDirectories(Set<StandardConfigDataReference> references) {
+	private Collection<StandardConfigDataResource> resolveEmptyDirectories(
+			Set<StandardConfigDataReference> references) {
+		Set<StandardConfigDataResource> empty = new LinkedHashSet<>();
 		for (StandardConfigDataReference reference : references) {
-			if (reference.isNonOptionalDirectory()) {
-				assertDirectoryExists(reference);
+			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));
 			}
 		}
-	}
-
-	private void assertDirectoryExists(StandardConfigDataReference reference) {
-		Resource resource = this.resourceLoader.getResource(reference.getDirectory());
-		if (!(resource instanceof ClassPathResource)) {
-			StandardConfigDataResource configDataResource = new StandardConfigDataResource(reference, resource);
-			ConfigDataResourceNotFoundException.throwIfDoesNotExist(configDataResource, resource);
-		}
+		return empty;
 	}
 
 	private List<StandardConfigDataResource> resolve(StandardConfigDataReference reference) {

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

@@ -66,7 +66,7 @@ String getResourceLocation() {
 		return this.resourceLocation;
 	}
 
-	boolean isNonOptionalDirectory() {
+	boolean isMandatoryDirectory() {
 		return !this.configDataLocation.isOptional() && this.directory != null;
 	}
 

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

@@ -36,16 +36,29 @@ public class StandardConfigDataResource extends ConfigDataResource {
 
 	private final Resource resource;
 
+	private boolean emptyDirectory;
+
 	/**
 	 * Create a new {@link StandardConfigDataResource} instance.
 	 * @param reference the resource reference
 	 * @param resource the underlying resource
 	 */
 	StandardConfigDataResource(StandardConfigDataReference reference, Resource resource) {
+		this(reference, resource, false);
+	}
+
+	/**
+	 * Create a new {@link StandardConfigDataResource} instance.
+	 * @param reference the resource reference
+	 * @param resource the underlying resource
+	 * @param emptyDirectory if the resource is an empty directory that we know exists
+	 */
+	StandardConfigDataResource(StandardConfigDataReference reference, Resource resource, boolean emptyDirectory) {
 		Assert.notNull(reference, "Reference must not be null");
 		Assert.notNull(resource, "Resource must not be null");
 		this.reference = reference;
 		this.resource = resource;
+		this.emptyDirectory = emptyDirectory;
 	}
 
 	StandardConfigDataReference getReference() {
@@ -56,6 +69,10 @@ Resource getResource() {
 		return this.resource;
 	}
 
+	boolean isEmptyDirectory() {
+		return this.emptyDirectory;
+	}
+
 	@Override
 	public boolean equals(Object obj) {
 		if (this == obj) {
@@ -65,7 +82,7 @@ public boolean equals(Object obj) {
 			return false;
 		}
 		StandardConfigDataResource other = (StandardConfigDataResource) obj;
-		return this.resource.equals(other.resource);
+		return this.resource.equals(other.resource) && this.emptyDirectory == other.emptyDirectory;
 	}
 
 	@Override

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

@@ -61,6 +61,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 
 /**
  * Integration tests for {@link ConfigDataEnvironmentPostProcessor}.
@@ -535,6 +536,14 @@ void runWhenConfigLocationHasNonOptionalMissingClasspathDirectoryThrowsLocationN
 				.isThrownBy(() -> this.application.run("--spring.config.location=" + location));
 	}
 
+	@Test
+	void runWhenConfigLocationHasNonOptionalEmptyFileDirectoryDoesNotThrowException() {
+		File location = new File(this.temp, "application.empty");
+		location.mkdirs();
+		assertThatNoException().isThrownBy(() -> this.application
+				.run("--spring.config.location=" + StringUtils.cleanPath(location.getAbsolutePath()) + "/"));
+	}
+
 	@Test
 	@Disabled("Disabled until spring.profiles suppport is dropped")
 	void runWhenUsingInvalidPropertyThrowsException() {