Allow using AnnotationCreator to represent nested annotations

src/main/java/io/quarkus/gizmo/AnnotationCreator.java

@@ -16,8 +16,74 @@
 
 package io.quarkus.gizmo;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
 public interface AnnotationCreator {
+    /**
+     * Returns an {@link AnnotationCreator} for annotation of given {@code annotationType}.
+     * <p>
+     * Useful for representing nested annotations (see {@link #addValue(String, Object) addValue}).
+     *
+     * @param annotationType class name of the annotation to create, must not be {@code null}
+     * @return an {@code AnnotationCreator}, never {@code null}
+     */
+    static AnnotationCreator of(String annotationType) {
+        return of(annotationType, RetentionPolicy.RUNTIME);
+    }
 
-    void addValue(String name, Object value);
+    /**
+     * Returns an {@link AnnotationCreator} for annotation of given {@code annotationType}.
+     * <p>
+     * Useful for representing nested annotations (see {@link #addValue(String, Object) addValue}).
+     *
+     * @param annotationType type of the annotation to create, must not be {@code null}
+     * @return an {@code AnnotationCreator}, never {@code null}
+     */
+    static AnnotationCreator of(Class<?> annotationType) {
+        Retention retention = annotationType.getAnnotation(Retention.class);
+        return of(annotationType.getName(), retention == null ? RetentionPolicy.SOURCE : retention.value());
+    }
+
+    /**
+     * Returns an {@link AnnotationCreator} for annotation of given {@code annotationType}
+     * which has given {@code retentionPolicy}.
+     * <p>
+     * Useful for representing nested annotations (see {@link #addValue(String, Object) addValue}).
+     *
+     * @param annotationType class name of the annotation to create, must not be {@code null}
+     * @param retentionPolicy retention policy of the annotation type
+     * @return an {@code AnnotationCreator}, never {@code null}
+     */
+    static AnnotationCreator of(String annotationType, RetentionPolicy retentionPolicy) {
+        return new AnnotationCreatorImpl(annotationType, retentionPolicy);
+    }
 
+    /**
+     * Same as {@link #addValue(String, Object)}, but returns {@code this} to allow fluent usage.
+     */
+    default AnnotationCreator add(String name, Object value) {
+        addValue(name, value);
+        return this;
+    }
+
+    /**
+     * Add a new annotation element with the given {@code name} and {@code value}. The name may be any permissible
+     * annotation element name (for example, {@code toString} or {@code annotationType} are invalid). The value may be:
+     * <ul>
+     * <li>primitive wrapper type</li>
+     * <li>{@link String}</li>
+     * <li>{@link Enum}</li>
+     * <li>{@link Class}</li>
+     * <li>nested annotation as an {@link AnnotationCreator} created using {@code AnnotationCreator.of()},
+     * or as a Jandex {@link org.jboss.jandex.AnnotationInstance AnnotationInstance}</li>
+     * <li>array of previously mentioned types</li>
+     * </ul>
+     * In addition to the types listed above, the value may also be a Jandex
+     * {@link org.jboss.jandex.AnnotationValue AnnotationValue}.
+     *
+     * @param name name of the annotation element to add
+     * @param value value of the annotation element to add
+     */
+    void addValue(String name, Object value);
 }

src/main/java/io/quarkus/gizmo/AnnotationCreatorImpl.java

@@ -16,9 +16,7 @@
 
 package io.quarkus.gizmo;
 
-import java.lang.annotation.Annotation;
 import java.lang.annotation.RetentionPolicy;
-import java.lang.reflect.Method;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
@@ -39,8 +37,7 @@ class AnnotationCreatorImpl implements AnnotationCreator {
     @Override
     public void addValue(String name, Object value) {
         // TODO: Maybe typecheck value to ensure it matches the corresponding element type?
-        // TODO: If value is a Map, check if all its keys are elements for the annotation, and there are no
-        //       missing required elements
+        // TODO: If value is a nested annotation, check for nonexistent or missing elements?
         values.put(name, value);
     }
 

src/main/java/io/quarkus/gizmo/AnnotationUtils.java

@@ -1,13 +1,11 @@
 package io.quarkus.gizmo;
 
-import java.lang.annotation.Annotation;
 import java.lang.reflect.Array;
 import java.util.Map;
 
 import org.jboss.jandex.AnnotationInstance;
 import org.jboss.jandex.AnnotationValue;
 import org.objectweb.asm.AnnotationVisitor;
-import org.objectweb.asm.Type;
 
 final class AnnotationUtils {
 
@@ -28,24 +26,15 @@ static void visitAnnotationValue(AnnotationVisitor visitor, String key, Object v
                 visitAnnotationValue(nestedVisitor, annotationValue.name(), annotationValue);
             }
             nestedVisitor.visitEnd();
-        } else if (value instanceof Map) {
-            Map<String, Object> annotationValueMap = (Map<String, Object>) value;
-            if (!annotationValueMap.containsKey("annotationType")) {
-                throw new IllegalStateException("The annotationValueMap (" + annotationValueMap + ") does not have entry for " +
-                        "required value \"annotationType\".");
+        } else if (value instanceof AnnotationCreator) {
+            if (!(value instanceof AnnotationCreatorImpl)) {
+                throw new IllegalArgumentException("Custom implementations of AnnotationCreator are not accepted");
             }
-            Class<? extends Annotation> annotationType = (Class<? extends Annotation>) annotationValueMap.get("annotationType");
-            String descriptor = Type.getDescriptor(annotationType);
+            AnnotationCreatorImpl nested = (AnnotationCreatorImpl) value;
+            String descriptor = DescriptorUtils.objectToDescriptor(nested.getAnnotationType());
             AnnotationVisitor nestedVisitor = visitor.visitAnnotation(key, descriptor);
-            for (Map.Entry<String, Object> annotationInstanceValueEntry : annotationValueMap.entrySet()) {
-                final String parameterName = annotationInstanceValueEntry.getKey();
-                final Object parameterValue = annotationInstanceValueEntry.getValue();
-
-                if (parameterName.equals("annotationType")) {
-                    continue;
-                }
-
-                visitAnnotationValue(nestedVisitor, parameterName, parameterValue);
+            for (Map.Entry<String, Object> member : nested.getValues().entrySet()) {
+                visitAnnotationValue(nestedVisitor, member.getKey(), member.getValue());
             }
             nestedVisitor.visitEnd();
         } else if (value instanceof AnnotationValue) {