Merge branch '3.1.x'

Closes gh-36857

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/logback/LogbackLoggingSystem.java

@@ -250,20 +250,29 @@ public class LogbackLoggingSystem extends AbstractLoggingSystem implements BeanF
 	}
 
 	private void reportConfigurationErrorsIfNecessary(LoggerContext loggerContext) {
-		List<Status> statuses = loggerContext.getStatusManager().getCopyOfStatusList();
 		StringBuilder errors = new StringBuilder();
-		for (Status status : statuses) {
+		List<Throwable> suppressedExceptions = new ArrayList<>();
+		for (Status status : loggerContext.getStatusManager().getCopyOfStatusList()) {
 			if (status.getLevel() == Status.ERROR) {
 				errors.append((errors.length() > 0) ? String.format("%n") : "");
 				errors.append(status.toString());
+				if (status.getThrowable() != null) {
+					suppressedExceptions.add(status.getThrowable());
 				}
 			}
-		if (errors.length() > 0) {
-			throw new IllegalStateException(String.format("Logback configuration error detected: %n%s", errors));
 		}
+		if (errors.length() == 0) {
 			if (!StatusUtil.contextHasStatusListener(loggerContext)) {
 				StatusPrinter.printInCaseOfErrorsOrWarnings(loggerContext);
 			}
+			return;
+		}
+		IllegalStateException ex = new IllegalStateException(
+				String.format("Logback configuration error detected: %n%s", errors));
+		for (Throwable suppressedException : suppressedExceptions) {
+			ex.addSuppressed(suppressedException);
+		}
+		throw ex;
 	}
 
 	private void configureByResourceUrl(LoggingInitializationContext initializationContext, LoggerContext loggerContext,

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemTests.java

@@ -38,6 +38,7 @@ import ch.qos.logback.core.ConsoleAppender;
 import ch.qos.logback.core.encoder.LayoutWrappingEncoder;
 import ch.qos.logback.core.rolling.RollingFileAppender;
 import ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy;
+import ch.qos.logback.core.util.DynamicClassLoadingException;
 import ch.qos.logback.core.util.StatusPrinter;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -771,6 +772,16 @@ class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
 		assertThat(getLineWithText(output, "Hello world")).doesNotContain("myapp");
 	}
 
+	@Test
+	void whenConfigurationErrorIsDetectedUnderlyingCausesAreIncludedAsSuppressedExceptions() {
+		this.loggingSystem.beforeInitialize();
+		assertThatIllegalStateException()
+			.isThrownBy(() -> initialize(this.initializationContext, "classpath:logback-broken.xml",
+					getLogFile(tmpDir() + "/tmp.log", null)))
+			.satisfies((ex) -> assertThat(ex.getSuppressed())
+				.hasAtLeastOneElementOfType(DynamicClassLoadingException.class));
+	}
+
 	private void initialize(LoggingInitializationContext context, String configLocation, LogFile logFile) {
 		this.loggingSystem.getSystemProperties((ConfigurableEnvironment) context.getEnvironment()).apply(logFile);
 		this.loggingSystem.beforeInitialize();