ArC: add ObserverTranformer test to the core test suite

independent-projects/arc/tests/src/test/java/io/quarkus/arc/test/buildextension/observers/ObservertransformerTest.java

@@ -0,0 +1,97 @@
+package io.quarkus.arc.test.buildextension.observers;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import jakarta.annotation.Priority;
+import jakarta.enterprise.event.Event;
+import jakarta.enterprise.event.Observes;
+import jakarta.enterprise.event.Reception;
+import jakarta.enterprise.util.AnnotationLiteral;
+import jakarta.inject.Qualifier;
+import jakarta.inject.Singleton;
+
+import org.jboss.jandex.AnnotationInstance;
+import org.jboss.jandex.Type;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.arc.Arc;
+import io.quarkus.arc.processor.ObserverTransformer;
+import io.quarkus.arc.test.ArcTestContainer;
+
+public class ObservertransformerTest {
+
+    @RegisterExtension
+    public ArcTestContainer container = ArcTestContainer.builder().beanClasses(MyObserver.class, AlphaQualifier.class)
+            .observerTransformers(new ObserverTransformer() {
+
+                @Override
+                public void transform(TransformationContext context) {
+                    context.transform()
+                            .reception(Reception.IF_EXISTS)
+                            .priority(1)
+                            .done();
+                }
+
+                @Override
+                public boolean appliesTo(Type observedType, Set<AnnotationInstance> qualifiers) {
+                    // observed type is String and qualifiers: @AlphaQualifier
+                    return observedType.name().toString().equals(String.class.getName()) && qualifiers.size() == 1
+                            && qualifiers.iterator().next().name().toString().equals(AlphaQualifier.class.getName());
+                }
+            }).build();
+
+    @Test
+    public void testTransformedObserver() {
+        MyObserver.EVENTS.clear();
+
+        @SuppressWarnings("serial")
+        Event<String> event = Arc.container().beanManager().getEvent().select(String.class,
+                new AnnotationLiteral<AlphaQualifier>() {
+                });
+        event.fire("foo");
+        // Reception was transformed to IF_EXISTS so test1() is not invoked
+        assertEquals(List.of("foo_MyObserver2"), MyObserver.EVENTS);
+        MyObserver.EVENTS.clear();
+
+        event.fire("foo");
+        assertEquals(List.of("foo_MyObserver1", "foo_MyObserver2"), MyObserver.EVENTS);
+    }
+
+    @Singleton
+    static class MyObserver {
+
+        static final List<String> EVENTS = new CopyOnWriteArrayList<String>();
+
+        // Transformed to test1(@Observes(reception = IF_EXISTS) @Priority(1) @AlphaQualifier String event)
+        void test1(@Observes @AlphaQualifier String event) {
+            EVENTS.add(event + "_MyObserver1");
+        }
+
+        void test2(@Observes @Priority(10) String event) {
+            EVENTS.add(event + "_MyObserver2");
+        }
+
+    }
+
+    @Qualifier
+    @Inherited
+    @Target({ TYPE, METHOD, FIELD, PARAMETER })
+    @Retention(RUNTIME)
+    public @interface AlphaQualifier {
+
+    }
+
+}