Fix logging with panache in interfaces

core/deployment/src/main/java/io/quarkus/deployment/logging/LoggingWithPanacheProcessor.java

@@ -43,7 +43,8 @@ public void process(CombinedIndexBuildItem index, BuildProducer<BytecodeTransfor
     /**
      * Makes the following modifications to the visited class:
      * <ul>
-     * <li>adds a {@code private static final} field of type {@code org.jboss.logging.Logger};</li>
+     * <li>adds a {@code private static final} field of type {@code org.jboss.logging.Logger}
+     * ({@code public} in case the class is an interface, to obey the JVMS rules);</li>
      * <li>initializes the field (to {@code Logger.getLogger(className)}) at the beginning of the
      * static initializer (creating one if missing);</li>
      * <li>rewrites all invocations of {@code static} methods on {@code io.quarkus.logging.Log}
@@ -57,6 +58,8 @@ private static class AddLoggerFieldAndRewriteInvocations extends ClassVisitor {
         private final String className;
         private final String classNameBinary;
 
+        private boolean isInterface;
+
         private boolean generatedLoggerField;
         private boolean generatedLoggerFieldInitialization;
 
@@ -66,6 +69,14 @@ public AddLoggerFieldAndRewriteInvocations(ClassVisitor visitor, String classNam
             this.classNameBinary = className.replace(".", "/");
         }
 
+        @Override
+        public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+            super.visit(version, access, name, signature, superName, interfaces);
+            if ((access & Opcodes.ACC_INTERFACE) != 0) {
+                isInterface = true;
+            }
+        }
+
         @Override
         public FieldVisitor visitField(int access, String name, String descriptor, String signature, Object value) {
             if (!generatedLoggerField) {
@@ -190,8 +201,11 @@ public void visitEnd() {
         }
 
         private void generateLoggerField() {
-            super.visitField(Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL,
-                    SYNTHETIC_LOGGER_FIELD_NAME, JBOSS_LOGGER_DESCRIPTOR, null, null);
+            // interface fields must be public static final per the JVMS
+            int access = isInterface
+                    ? Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL
+                    : Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL;
+            super.visitField(access, SYNTHETIC_LOGGER_FIELD_NAME, JBOSS_LOGGER_DESCRIPTOR, null, null);
             generatedLoggerField = true;
         }
     }

integration-tests/logging-panache/src/test/java/io/quarkus/logging/LoggingBean.java

@@ -4,7 +4,7 @@
 import javax.inject.Singleton;
 
 @Singleton
-public class LoggingBean {
+public class LoggingBean implements LoggingInterface {
     // not final to prevent constant inlining
     private static String msg = "Heya!";
 
@@ -18,6 +18,8 @@ public void setup() {
     }
 
     public void doSomething() {
+        inheritedMethod("abc");
+
         if (Log.isDebugEnabled()) {
             Log.debug("starting massive computation");
         }

integration-tests/logging-panache/src/test/java/io/quarkus/logging/LoggingInterface.java

@@ -0,0 +1,9 @@
+package io.quarkus.logging;
+
+public interface LoggingInterface {
+    default void inheritedMethod(String param) {
+        if (Log.isInfoEnabled()) {
+            Log.infof("Default method from interface: %s", param);
+        }
+    }
+}

integration-tests/logging-panache/src/test/java/io/quarkus/logging/LoggingWithPanacheTest.java

@@ -17,8 +17,8 @@
 public class LoggingWithPanacheTest {
     @RegisterExtension
     static final QuarkusUnitTest test = new QuarkusUnitTest()
-            .withApplicationRoot((jar) -> jar
-                    .addClasses(LoggingBean.class, LoggingEntity.class, NoStackTraceTestException.class))
+            .withApplicationRoot((jar) -> jar.addClasses(LoggingBean.class, LoggingInterface.class, LoggingEntity.class,
+                    NoStackTraceTestException.class))
             .overrideConfigKey("quarkus.log.category.\"io.quarkus.logging\".min-level", "TRACE")
             .overrideConfigKey("quarkus.log.category.\"io.quarkus.logging\".level", "TRACE")
             .setLogRecordPredicate(record -> record.getLoggerName().startsWith("io.quarkus.logging.Logging"))
@@ -29,6 +29,7 @@ public class LoggingWithPanacheTest {
                 assertThat(lines).containsExactly(
                         "[INFO] Heya!",
                         "[TRACE] LoggingBean created",
+                        "[INFO] Default method from interface: abc",
                         "[DEBUG] starting massive computation",
                         "[DEBUG] one: 42",
                         "[TRACE] two: 42 | 13",