8005295: Use mandated information for printing of repeating annotations

src/jdk.compiler/share/classes/com/sun/tools/javac/processing/PrintingProcessor.java

@@ -522,9 +522,82 @@ private String annotationsToString(Element e) {
         private void printAnnotations(Element e) {
             List<? extends AnnotationMirror> annots = e.getAnnotationMirrors();
             for(AnnotationMirror annotationMirror : annots) {
-                indent();
-                writer.println(annotationMirror);
+                // Handle compiler-generated container annotations specially
+                if (!printedContainerAnnotation(e, annotationMirror)) {
+                    indent();
+                    writer.println(annotationMirror);
+                }
+            }
+        }
+
+        private boolean printedContainerAnnotation(Element e,
+                                                   AnnotationMirror annotationMirror) {
+            /*
+             * If the annotation mirror is marked as mandated and
+             * looks like a container annotation, elide printing the
+             * container and just print the wrapped contents.
+             */
+            if (elementUtils.getOrigin(e, annotationMirror) == Elements.Origin.MANDATED) {
+                // From JLS Chapter 9, an annotation interface AC is a
+                // containing annotation interface of A if AC declares
+                // a value() method whose return type is A[] and any
+                // methods declared by AC other than value() have a
+                // default value. As an implementation choice, if more
+                // than one annotation element is found on the outer
+                // annotation, in other words, something besides a
+                // "value" method, the annotation will not be treated
+                // as a wrapper for the purposes of printing. These
+                // checks are intended to preserve correctness in the
+                // face of some other kind of annotation being marked
+                // as mandated.
+
+                var entries = annotationMirror.getElementValues().entrySet();
+                if (entries.size() == 1) {
+                    var annotationType = annotationMirror.getAnnotationType();
+                    var annotationTypeAsElement = annotationType.asElement();
+
+                    var entry = entries.iterator().next();
+                    var annotationElements = entry.getValue();
+
+                    // Check that the annotation type declaration has
+                    // a single method named "value" and that it
+                    // returns an array. A stricter check would be
+                    // that it is an array of an annotation type and
+                    // that annotation type in turn was repeatable.
+                    if (annotationTypeAsElement.getKind() == ElementKind.ANNOTATION_TYPE) {
+                        var annotationMethods =
+                            ElementFilter.methodsIn(annotationTypeAsElement.getEnclosedElements());
+                        if (annotationMethods.size() == 1) {
+                            var valueMethod = annotationMethods.get(0);
+                            var returnType = valueMethod.getReturnType();
+
+                            if ("value".equals(valueMethod.getSimpleName().toString()) &&
+                                returnType.getKind() == TypeKind.ARRAY) {
+                                // Use annotation value visitor that
+                                // returns a boolean if it prints out
+                                // contained annotations as expected
+                                // and false otherwise
+
+                                return (new SimpleAnnotationValueVisitor14<Boolean, Void>(false) {
+                                    @Override
+                                    public Boolean visitArray(List<? extends AnnotationValue> vals, Void p) {
+                                        if (vals.size() < 2) {
+                                            return false;
+                                        } else {
+                                            for (var annotValue: vals) {
+                                                indent();
+                                                writer.println(annotValue.toString());
+                                            }
+                                            return true;
+                                        }
+                                    }
+                                }).visit(annotationElements);
+                            }
+                        }
+                    }
+                }
             }
+            return false;
         }
 
         // TODO: Refactor

test/langtools/tools/javac/processing/options/XprintRepeatingAnnotations.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8005295
+ * @summary Verify repeating annotations are printed as expected
+ * @compile/ref=XprintRepeatingAnnotations.out -Xprint  XprintRepeatingAnnotations.java
+ */
+
+import java.lang.annotation.*;
+import static java.lang.annotation.RetentionPolicy.*;
+
+@Foo(1)
+@Foo(2)
+@Bar(3)
+@Bar(4)
+public class XprintRepeatingAnnotations {
+}
+
+@Retention(RUNTIME)
+@Documented
+@Repeatable(Foos.class)
+@interface Foo {
+    int value();
+}
+
+@Retention(RUNTIME)
+@Documented
+@interface Foos {
+    Foo[] value();
+}
+
+@Retention(RUNTIME)
+@Documented
+@Repeatable(Bars.class)
+@interface Bar {
+    int value();
+}
+
+@Retention(RUNTIME)
+@Documented
+@interface Bars {
+    Bar[] value();
+    int quux() default 1;
+}

test/langtools/tools/javac/processing/options/XprintRepeatingAnnotations.out

@@ -0,0 +1,40 @@
+
+@Foo(1)
+@Foo(2)
+@Bars({@Bar(3), @Bar(4)})
+public class XprintRepeatingAnnotations {
+
+  public XprintRepeatingAnnotations();
+}
+
+@java.lang.annotation.Retention(RUNTIME)
+@java.lang.annotation.Documented
+@java.lang.annotation.Repeatable(Foos.class)
+@interface Foo {
+
+  int value();
+}
+
+@java.lang.annotation.Retention(RUNTIME)
+@java.lang.annotation.Documented
+@interface Foos {
+
+  Foo[] value();
+}
+
+@java.lang.annotation.Retention(RUNTIME)
+@java.lang.annotation.Documented
+@java.lang.annotation.Repeatable(Bars.class)
+@interface Bar {
+
+  int value();
+}
+
+@java.lang.annotation.Retention(RUNTIME)
+@java.lang.annotation.Documented
+@interface Bars {
+
+  Bar[] value();
+
+  int quux() default 1;
+}