Consider the underling file in equals/hashcode

Update `StandardConfigDataResource` so that the underlying file is
considered in equals/hashcode. Prior to this commit, if the classpath
included `.` then the same resource could be loaded twice. Once via
a `ClassPathResource` and once via a `FileSystemResource`.

Fixes gh-34212

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -28,6 +28,7 @@ import java.util.Set;
 import org.apache.commons.logging.Log;
 
 import org.springframework.boot.logging.DeferredLogFactory;
+import org.springframework.core.log.LogMessage;
 
 /**
  * Imports {@link ConfigData} by {@link ConfigDataLocationResolver resolving} and
@@ -117,16 +118,20 @@ class ConfigDataImporter {
 			ConfigDataResolutionResult candidate = candidates.get(i);
 			ConfigDataLocation location = candidate.getLocation();
 			ConfigDataResource resource = candidate.getResource();
+			this.logger.trace(LogMessage.format("Considering resource %s from location %s", resource, location));
 			if (resource.isOptional()) {
 				this.optionalLocations.add(location);
 			}
 			if (this.loaded.contains(resource)) {
+				this.logger
+					.trace(LogMessage.format("Already loaded resource %s ignoring location %s", resource, location));
 				this.loadedLocations.add(location);
 			}
 			else {
 				try {
 					ConfigData loaded = this.loaders.load(loaderContext, resource);
 					if (loaded != null) {
+						this.logger.trace(LogMessage.format("Loaded resource %s from location %s", resource, location));
 						this.loaded.add(resource);
 						this.loadedLocations.add(location);
 						result.put(candidate, loaded);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -16,8 +16,10 @@
 
 package org.springframework.boot.context.config;
 
+import java.io.File;
 import java.io.IOException;
 
+import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.FileUrlResource;
 import org.springframework.core.io.Resource;
@@ -96,12 +98,21 @@ public class StandardConfigDataResource extends ConfigDataResource {
 			return false;
 		}
 		StandardConfigDataResource other = (StandardConfigDataResource) obj;
-		return this.resource.equals(other.resource) && this.emptyDirectory == other.emptyDirectory;
+		return (this.emptyDirectory == other.emptyDirectory) && isSameUnderlyingResource(this.resource, other.resource);
+	}
+
+	private boolean isSameUnderlyingResource(Resource ours, Resource other) {
+		return ours.equals(other) || isSameFile(getUnderlyingFile(ours), getUnderlyingFile(other));
+	}
+
+	private boolean isSameFile(File ours, File other) {
+		return (ours != null) && (other != null) && ours.equals(other);
 	}
 
 	@Override
 	public int hashCode() {
-		return this.resource.hashCode();
+		File underlyingFile = getUnderlyingFile(this.resource);
+		return (underlyingFile != null) ? underlyingFile.hashCode() : this.resource.hashCode();
 	}
 
 	@Override
@@ -116,4 +127,17 @@ public class StandardConfigDataResource extends ConfigDataResource {
 		return this.resource.toString();
 	}
 
+	private File getUnderlyingFile(Resource resource) {
+		try {
+			if (resource instanceof ClassPathResource || resource instanceof FileSystemResource
+					|| resource instanceof FileUrlResource) {
+				File file = resource.getFile();
+				return (file != null) ? file.getAbsoluteFile() : null;
+			}
+		}
+		catch (IOException ex) {
+		}
+		return null;
+	}
+
 }

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

@@ -16,9 +16,12 @@
 
 package org.springframework.boot.context.config;
 
+import java.io.IOException;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.FileUrlResource;
 import org.springframework.core.io.Resource;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -66,4 +69,15 @@ class StandardConfigDataResourceTests {
 		assertThat(location).isNotEqualTo(other);
 	}
 
+	@Test // gh-34212
+	void equalsAndHashCodeWhenSameUnderlyingResource() throws IOException {
+		ClassPathResource classPathResource = new ClassPathResource("log4j2.springboot");
+		FileUrlResource fileUrlResource = new FileUrlResource(classPathResource.getURL());
+		ConfigDataResource classPathConfigDataResource = new StandardConfigDataResource(this.reference,
+				classPathResource);
+		ConfigDataResource fileUrlConfigDataResource = new StandardConfigDataResource(this.reference, fileUrlResource);
+		assertThat(classPathConfigDataResource.hashCode()).isEqualTo(fileUrlConfigDataResource.hashCode());
+		assertThat(classPathConfigDataResource).isEqualTo(fileUrlConfigDataResource);
+	}
+
 }