From 254713ab598f186fd31484a48a6dfebaeb752920 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hannes=20Walln=C3=B6fer?= <hannesw@openjdk.org>
Date: Wed, 21 May 2025 14:37:30 +0000
Subject: [PATCH] 8338833: Error on reference not found for a snippet target

Reviewed-by: prappo
---
 .../formats/html/taglets/SnippetTaglet.java   | 15 +++---
 .../testSnippetTag/TestSnippetMarkup.java     | 48 ++++++++++++++++++-
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/taglets/SnippetTaglet.java b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/taglets/SnippetTaglet.java
index b166f4588ce..32bcab0eef5 100644
--- a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/taglets/SnippetTaglet.java
+++ b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/taglets/SnippetTaglet.java
@@ -136,7 +136,7 @@ public class SnippetTaglet extends BaseTaglet {
             if (styles.isEmpty()) {
                 code.add(text);
             } else {
-                Element e = null;
+                Element ref = null;
                 String linkTarget = null;
                 boolean markupEncountered = false;
                 Set<String> classes = new HashSet<>();
@@ -152,9 +152,11 @@ public class SnippetTaglet extends BaseTaglet {
                                         content.asCharSequence().toString().trim());
                             }
                             linkTarget = l.target();
-                            e = getLinkedElement(element, linkTarget);
-                            if (e == null) {
-                                // TODO: diagnostic output
+                            ref = getLinkedElement(element, linkTarget);
+                            if (ref == null) {
+                                messages.error(utils.getCommentHelper(element).getDocTreePath(tag),
+                                        "doclet.link.see.reference_not_found",
+                                        linkTarget);
                             }
                         }
                         case Style.Markup m -> markupEncountered = true;
@@ -164,7 +166,6 @@ public class SnippetTaglet extends BaseTaglet {
                 if (markupEncountered) {
                     return;
                 } else if (linkTarget != null) {
-                    assert e != null;
                     //disable preview tagging inside the snippets:
                     Utils.PreviewFlagProvider prevPreviewProvider = utils.setPreviewFlagProvider(el -> false);
                     try {
@@ -172,10 +173,10 @@ public class SnippetTaglet extends BaseTaglet {
                         c = lt.linkSeeReferenceOutput(element,
                                 null,
                                 linkTarget,
-                                e,
+                                ref,
                                 false, // TODO: for now
                                 Text.of(sequence.toString()),
-                                (key, args) -> { /* TODO: report diagnostic */ },
+                                (key, args) -> { /* Error has already been reported above */ },
                                 tagletWriter);
                     } finally {
                         utils.setPreviewFlagProvider(prevPreviewProvider);
diff --git a/test/langtools/jdk/javadoc/doclet/testSnippetTag/TestSnippetMarkup.java b/test/langtools/jdk/javadoc/doclet/testSnippetTag/TestSnippetMarkup.java
index 62782758215..a3e92584ae2 100644
--- a/test/langtools/jdk/javadoc/doclet/testSnippetTag/TestSnippetMarkup.java
+++ b/test/langtools/jdk/javadoc/doclet/testSnippetTag/TestSnippetMarkup.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 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
@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 8266666 8281969 8319339
+ * @bug 8266666 8281969 8319339 8338833
  * @summary Implementation for snippets
  * @library /tools/lib ../../lib
  * @modules jdk.compiler/com.sun.tools.javac.api
@@ -206,6 +206,50 @@ public class TestSnippetMarkup extends SnippetTester {
         testPositive(base, testCases);
     }
 
+    /*
+     * Make sure an error is generated for links with invalid reference.
+     */
+    @Test
+    public void testLinkReferenceNotFound(Path base) throws Exception {
+        Path srcDir = base.resolve("src");
+        Path outDir = base.resolve("out");
+
+        new ClassBuilder(tb, "pkg.A")
+                .setModifiers("public", "class")
+                .addMembers(
+                        ClassBuilder.MethodBuilder
+                                .parse("public void inline() { }")
+                                .setComments("""
+                                    First sentence.
+                                    {@snippet :
+                                        First line  // @link substring="First" target="String"
+                                        Second line // @link substring="Second" target="StringReader"
+                                    }
+                                """))
+                .write(srcDir);
+
+        javadoc("-d", outDir.toString(),
+                "-sourcepath", srcDir.toString(),
+                "pkg");
+
+        checkExit(Exit.ERROR);
+        checkOutput(Output.OUT, false,
+                """
+                        error: reference not found: String
+                        """);
+        checkOutput(Output.OUT, true,
+                """
+                        A.java:5: error: reference not found: StringReader
+                        """);
+        checkOutput("pkg/A.html", true,
+                """
+                        <details class="invalid-tag">
+                        <summary>invalid reference</summary>
+                        <pre><code>Second</code></pre>
+                        </details>""");
+        checkNoCrashes();
+    }
+
     @Test
     public void testCornerCases(Path base) throws Exception {
         var testCases = List.of(