8346109: Create JDK taglet for additional preview notes

Reviewed-by: ihse, liach, rriggs

make/Docs.gmk

@@ -79,6 +79,8 @@ JAVADOC_TAGS := \
     -tag see \
     -taglet build.tools.taglet.ExtLink \
     -taglet build.tools.taglet.Incubating \
+    -taglet build.tools.taglet.PreviewNote \
+    --preview-note-tag previewNote \
     -tagletpath $(BUILDTOOLS_OUTPUTDIR)/jdk_tools_classes \
     $(CUSTOM_JAVADOC_TAGS) \
     #

make/jdk/src/classes/build/tools/taglet/PreviewNote.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2025, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package build.tools.taglet;
+
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Set;
+
+
+import javax.lang.model.element.Element;
+import javax.tools.Diagnostic;
+
+
+import com.sun.source.doctree.DocTree;
+import com.sun.source.doctree.UnknownInlineTagTree;
+import jdk.javadoc.doclet.Doclet;
+import jdk.javadoc.doclet.DocletEnvironment;
+import jdk.javadoc.doclet.Reporter;
+import jdk.javadoc.doclet.StandardDoclet;
+import jdk.javadoc.doclet.Taglet;
+
+import static com.sun.source.doctree.DocTree.Kind.UNKNOWN_INLINE_TAG;
+
+/**
+ * An inline tag to insert a note formatted as preview note.
+ * The tag can be used as follows:
+ *
+ * <pre>
+ * {&commat;previewNote jep-number [Preview note heading]}
+ * Preview note content
+ * {&commat;previewNote}
+ * </pre>
+ *
+ */
+public class PreviewNote implements Taglet {
+
+    static final String TAG_NAME = "previewNote";
+    Reporter reporter = null;
+
+    @Override
+    public void init(DocletEnvironment env, Doclet doclet) {
+        if (doclet instanceof StandardDoclet stdoclet) {
+            reporter = stdoclet.getReporter();
+        }
+    }
+
+    /**
+     * Returns the set of locations in which the tag may be used.
+     */
+    @Override
+    public Set<Location> getAllowedLocations() {
+        return EnumSet.allOf(Taglet.Location.class);
+    }
+
+    @Override
+    public boolean isInlineTag() {
+        return true;
+    }
+
+    @Override
+    public String getName() {
+        return TAG_NAME;
+    }
+
+    @Override
+    public String toString(List<? extends DocTree> tags, Element elem) {
+
+        for (DocTree tag : tags) {
+            if (tag.getKind() == UNKNOWN_INLINE_TAG) {
+                UnknownInlineTagTree inlineTag = (UnknownInlineTagTree) tag;
+                String[] content = inlineTag.getContent().toString().trim().split("\\s+", 2);
+                if (!content[0].isBlank()) {
+                    StringBuilder sb = new StringBuilder("""
+                       <div class="preview-block" style="margin-top:10px; display:block; max-width:max-content;">
+                       """);
+                    if (content.length == 2) {
+                        sb.append("""
+                                <div class="preview-label">
+                                """)
+                          .append(content[1])
+                          .append("""
+                                </div>
+                                """);
+                    }
+                    sb.append("""
+                            <div class="preview-comment">
+                            """);
+                    return sb.toString();
+                } else {
+                    return """
+                             </div>
+                             </div>
+                            """;
+                }
+            }
+        }
+
+        if (reporter == null) {
+            throw new IllegalArgumentException("@" + TAG_NAME + " taglet content must be begin or end");
+        }
+        reporter.print(Diagnostic.Kind.ERROR, "@" + TAG_NAME + " taglet content must be begin or end");
+        return "";
+    }
+}

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/PreviewListWriter.java

@@ -38,6 +38,7 @@ import jdk.javadoc.internal.doclets.toolkit.util.DocPaths;
 import jdk.javadoc.internal.doclets.toolkit.util.PreviewAPIListBuilder;
 import jdk.javadoc.internal.html.Content;
 import jdk.javadoc.internal.html.ContentBuilder;
+import jdk.javadoc.internal.html.HtmlId;
 import jdk.javadoc.internal.html.HtmlStyle;
 import jdk.javadoc.internal.html.HtmlTree;
 import jdk.javadoc.internal.html.Text;
@@ -96,6 +97,22 @@ public class PreviewListWriter extends SummaryListWriter<PreviewAPIListBuilder>
         }
     }
 
+    @Override
+    protected void addExtraSection(Content content) {
+        var notes = builder.getElementNotes();
+        if (!notes.isEmpty()) {
+            addSummaryAPI(notes, HtmlId.of("preview-api-notes"),
+                    "doclet.Preview_Notes_Elements", "doclet.Element", content);
+        }
+    }
+
+    @Override
+    protected void addExtraIndexLink(Content target) {
+        if (!builder.getElementNotes().isEmpty()) {
+            addIndexLink(HtmlId.of("preview-api-notes"), "doclet.Preview_Notes", target);
+        }
+    }
+
     @Override
     protected void addComments(Element e, Content desc) {
         List<? extends DocTree> tags = utils.getFirstSentenceTrees(e);

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/resources/standard.properties

@@ -136,6 +136,8 @@ doclet.Preview_API_Checkbox_Toggle_All=Toggle all
 doclet.Preview_JEP_URL=https://openjdk.org/jeps/{0}
 doclet.Preview_Label=Preview
 doclet.Preview_Mark=PREVIEW
+doclet.Preview_Notes=Preview API Notes
+doclet.Preview_Notes_Elements=Elements containing Preview Notes
 doclet.Restricted_Methods=Restricted Methods
 doclet.Restricted_Mark=RESTRICTED
 doclet.searchTag=Search Tag

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/BaseOptions.java

@@ -236,6 +236,14 @@ public abstract class BaseOptions {
      */
     private boolean noTimestamp = false;
 
+
+    /**
+     * Argument for command-line option {@code --preview-note-tag}.
+     * If set, the JavaDoc inline tag with the given name is considered
+     * a preview note and added to the preview API page.
+     */
+    private String previewNoteTag = null;
+
     /**
      * Argument for command-line option {@code -quiet}.
      * Suppress all messages
@@ -549,6 +557,14 @@ public abstract class BaseOptions {
                     }
                 },
 
+                new Hidden(resources, "--preview-note-tag", 1) {
+                    @Override
+                    public boolean process(String option, List<String> args) {
+                        previewNoteTag = args.getFirst();
+                        return true;
+                    }
+                },
+
                 new Hidden(resources, "-quiet") {
                     @Override
                     public boolean process(String opt, List<String> args) {
@@ -940,6 +956,12 @@ public abstract class BaseOptions {
         return noTimestamp;
     }
 
+    /**
+     * Argument for command-line option {@code --preview-note-tag}.
+     * Name of inline tag for preview notes.
+     */
+    public String previewNoteTag() { return previewNoteTag; }
+
     /**
      * Argument for command-line option {@code -quiet}.
      * Suppress all messages

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/WorkArounds.java

@@ -396,34 +396,6 @@ public class WorkArounds {
         return compilerOptions.isSet("accessInternalAPI");
     }
 
-    /**
-     * Returns a map containing {@code jdk.internal.javac.PreviewFeature.JEP} element values associated with the
-     * {@code jdk.internal.javac.PreviewFeature.Feature} enum constant identified by {@code feature}.
-     *
-     * This method uses internal javac features (although only reflectively).
-     *
-     * @param feature the name of the PreviewFeature.Feature enum value
-     * @return the map of PreviewFeature.JEP annotation element values, or an empty map
-     */
-    public Map<String, Object> getJepInfo(String feature) {
-        TypeElement featureType = elementUtils.getTypeElement("jdk.internal.javac.PreviewFeature.Feature");
-        TypeElement jepType = elementUtils.getTypeElement("jdk.internal.javac.PreviewFeature.JEP");
-        var featureVar = featureType.getEnclosedElements().stream()
-                .filter(e -> feature.equals(e.getSimpleName().toString())).findFirst();
-        if (featureVar.isPresent()) {
-            for (AnnotationMirror anno : featureVar.get().getAnnotationMirrors()) {
-                if (anno.getAnnotationType().asElement().equals(jepType)) {
-                    return anno.getElementValues().entrySet()
-                            .stream()
-                            .collect(Collectors.toMap(
-                                    e -> e.getKey().getSimpleName().toString(),
-                                    e -> e.getValue().getValue()));
-                }
-            }
-        }
-        return Map.of();
-    }
-
     /*
      * If a similar query is ever added to javax.lang.model, use that instead.
      */

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/util/PreviewAPIListBuilder.java

@@ -25,15 +25,22 @@
 
 package jdk.javadoc.internal.doclets.toolkit.util;
 
+import com.sun.source.doctree.DocTree;
+import com.sun.source.doctree.UnknownInlineTagTree;
 import jdk.javadoc.internal.doclets.toolkit.BaseConfiguration;
 
+import javax.lang.model.element.AnnotationMirror;
+import javax.lang.model.element.AnnotationValue;
 import javax.lang.model.element.Element;
+import javax.lang.model.element.ExecutableElement;
+import javax.lang.model.element.TypeElement;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
+import java.util.SortedSet;
 import java.util.TreeSet;
-import java.util.stream.Collectors;
 
 /**
  * Build list of all the preview packages, classes, constructors, fields and methods.
@@ -41,8 +48,9 @@ import java.util.stream.Collectors;
 public class PreviewAPIListBuilder extends SummaryAPIListBuilder {
 
     private final Map<Element, JEP> elementJeps = new HashMap<>();
+    private final SortedSet<Element> elementNotes = createSummarySet();
     private final Map<String, JEP> jeps = new HashMap<>();
-    private static final JEP NULL_SENTINEL = new JEP(0, "", "");
+    private final String previewNoteTag;
 
     /**
      * The JEP for a preview feature in this release.
@@ -61,39 +69,78 @@ public class PreviewAPIListBuilder extends SummaryAPIListBuilder {
      */
     public PreviewAPIListBuilder(BaseConfiguration configuration) {
         super(configuration);
-        buildSummaryAPIInfo();
+        this.previewNoteTag = configuration.getOptions().previewNoteTag();
+        // retrieve preview JEPs
+        buildPreviewFeatureInfo();
+        if (!jeps.isEmpty()) {
+            // map elements to preview JEPs and preview tags
+            buildSummaryAPIInfo();
+            // remove unused preview JEPs
+            jeps.entrySet().removeIf(e -> !elementJeps.containsValue(e.getValue()));
+        }
+    }
+
+    private void buildPreviewFeatureInfo() {
+        TypeElement featureType = utils.elementUtils.getTypeElement("jdk.internal.javac.PreviewFeature.Feature");
+        if (featureType == null) {
+            return;
+        }
+        TypeElement jepType = utils.elementUtils.getTypeElement("jdk.internal.javac.PreviewFeature.JEP");
+        featureType.getEnclosedElements().forEach(elem -> {
+            for (AnnotationMirror anno : elem.getAnnotationMirrors()) {
+                if (anno.getAnnotationType().asElement().equals(jepType)) {
+                    Map<? extends ExecutableElement, ? extends AnnotationValue> values = anno.getElementValues();
+                    jeps.put(elem.getSimpleName().toString(), new JEP(
+                            getAnnotationElementValue(values, "number", 0),
+                            getAnnotationElementValue(values, "title", ""),
+                            getAnnotationElementValue(values, "status", "Preview"))
+                    );
+                }
+            }
+        });
+    }
+
+    // Extract a single annotation element value with the given name and default value
+    @SuppressWarnings("unchecked")
+    private <R> R getAnnotationElementValue(Map<? extends ExecutableElement, ? extends AnnotationValue> values,
+                                            String name, R defaultValue) {
+        Optional<R> value = values.entrySet().stream()
+                .filter(e -> Objects.equals(e.getKey().getSimpleName().toString(), name))
+                .map(e -> (R) e.getValue().getValue())
+                .findFirst();
+        return value.orElse(defaultValue);
     }
 
     @Override
     protected boolean belongsToSummary(Element element) {
-        if (!utils.isPreviewAPI(element)) {
+        if (utils.isPreviewAPI(element)) {
-            return false;
+            String feature = Objects.requireNonNull(utils.getPreviewFeature(element),
-        }
+                    "Preview feature not specified").toString();
-        String feature = Objects.requireNonNull(utils.getPreviewFeature(element),
+            // Preview features without JEP are not included in the list.
-                "Preview feature not specified").toString();
+            JEP jep = jeps.get(feature);
-        JEP jep = jeps.computeIfAbsent(feature, featureName -> {
+            if (jep != null) {
-            Map<String, Object> jepInfo = configuration.workArounds.getJepInfo(featureName);
+                elementJeps.put(element, jep);
-            if (!jepInfo.isEmpty()) {
+                return true;
-                int number = 0;
+            }
-                String title = "";
+        }
-                String status = "Preview"; // Default value is not returned by the method we used above.
+        // If preview tag is defined map elements to preview tags
-                for (var entry : jepInfo.entrySet()) {
+        if (previewNoteTag != null) {
-                    switch (entry.getKey()) {
+            CommentHelper ch = utils.getCommentHelper(element);
-                        case "number" -> number = (int) entry.getValue();
+            if (ch.dcTree != null) {
-                        case "title" -> title = (String) entry.getValue();
+                var jep = ch.dcTree.getFullBody().stream()
-                        case "status" -> status = (String) entry.getValue();
+                        .filter(dt -> dt.getKind() == DocTree.Kind.UNKNOWN_INLINE_TAG)
-                        default -> throw new IllegalArgumentException(entry.getKey());
+                        .map(dt -> (UnknownInlineTagTree) dt)
-                    }
+                        .filter(t -> previewNoteTag.equals(t.getTagName()) && !t.getContent().isEmpty())
-                }
+                        .map(this::findJEP)
-                return new JEP(number, title, status);
+                        .filter(Objects::nonNull)
+                        .findFirst();
+                if (jep.isPresent()) {
+                    elementNotes.add(element);
+                    elementJeps.put(element, jep.get());
+                    // Don't return true as this is not actual preview API.
+                }
             }
-            return NULL_SENTINEL;
-        });
-        if (jep != NULL_SENTINEL) {
-            elementJeps.put(element, jep);
-            return true;
         }
-        // Preview features without JEP are not included.
         return false;
     }
 
@@ -101,10 +148,7 @@ public class PreviewAPIListBuilder extends SummaryAPIListBuilder {
      * {@return a sorted set of preview feature JEPs in this release}
      */
     public Set<JEP> getJEPs() {
-        return jeps.values()
+        return new TreeSet<>(jeps.values());
-                .stream()
-                .filter(jep -> jep != NULL_SENTINEL)
-                .collect(Collectors.toCollection(TreeSet::new));
     }
 
     /**
@@ -113,4 +157,26 @@ public class PreviewAPIListBuilder extends SummaryAPIListBuilder {
     public JEP getJEP(Element e) {
         return elementJeps.get(e);
     }
+
+    /**
+     * {@return a sorted set containing elements tagged with preview notes}
+     */
+    public SortedSet<Element> getElementNotes() {
+        return elementNotes;
+    }
+
+    private JEP findJEP(UnknownInlineTagTree tag) {
+        var content = tag.getContent().toString().trim().split("\\s+", 2);
+        try {
+            var jnum = Integer.parseInt(content[0]);
+            for (var jep : jeps.values()) {
+                if (jep.number == jnum) {
+                    return jep;
+                }
+            }
+        } catch (NumberFormatException nfe) {
+            // print warning?
+        }
+        return null;
+    }
 }

test/langtools/jdk/javadoc/doclet/testPreview/TestPreview.java

@@ -24,7 +24,7 @@
 /*
  * @test
  * @bug      8250768 8261976 8277300 8282452 8287597 8325325 8325874 8297879
- *           8331947 8281533 8343239 8318416
+ *           8331947 8281533 8343239 8318416 8346109
  * @summary  test generated docs for items declared using preview
  * @library  /tools/lib ../../lib
  * @modules jdk.javadoc/jdk.javadoc.internal.tool
@@ -296,4 +296,54 @@ public class TestPreview extends JavadocTester {
         checkOutput("m/module-summary.html", true,
                     "Indirect exports from the <code>java.base</code> module are");
     }
+
+    // Test for JDK hidden option to add an entry for a non-preview element
+    // in the preview page based on the presence of a javadoc tag.
+    @Test
+    public void testPreviewNoteTag(Path base) throws IOException {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, """
+                package p;
+                import jdk.internal.javac.PreviewFeature;
+
+                /**
+                 * Preview feature
+                 */
+                @PreviewFeature(feature= PreviewFeature.Feature.TEST)
+                public interface CoreInterface {
+                }
+                """, """
+                package p;
+
+                 /**
+                  * Non preview feature.
+                  * {@previewNote 2147483647 Preview API Note}
+                  */
+                 public interface NonPrevieFeature {
+                 }
+                """);
+        javadoc("-d", "out-preview-note-tag",
+                "--add-exports", "java.base/jdk.internal.javac=ALL-UNNAMED",
+                "-tag", "previewNote:a:Preview Note:",
+                "--preview-note-tag", "previewNote",
+                "--source-path",
+                src.toString(),
+                "p");
+        checkExit(Exit.OK);
+
+        checkOutput("preview-list.html", true,
+                """
+                    <h2 title="Contents">Contents</h2>
+                    <ul class="contents-list">
+                    <li id="contents-preview-api-notes"><a href="#preview-api-notes">Preview API Notes</a></li>
+                    <li id="contents-interface"><a href="#interface">Interfaces</a></li>""",
+                """
+                    <div class="caption"><span>Elements containing Preview Notes</span></div>""",
+                """
+                    <div class="col-summary-item-name even-row-color preview-api-notes preview-api-notes-tab1\
+                    "><a href="p/NonPrevieFeature.html" title="interface in p">p.NonPrevieFeature</a></div>
+                    <div class="col-second even-row-color preview-api-notes preview-api-notes-tab1">Test Feature</div>
+                    <div class="col-last even-row-color preview-api-notes preview-api-notes-tab1">
+                    <div class="block">Non preview feature.</div>""");
+    }
 }