8304878: ConcurrentModificationException in javadoc tool

Reviewed-by: jjg

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

@@ -2178,8 +2178,14 @@ public class Utils {
         if (path != null || elementToTreePath.containsKey(e)) {
             // expedite the path and one that is a null
             return path;
+        } else {
+            var p = docTrees.getPath(e);
+            // if docTrees.getPath itself has put a path for e into elementToTreePath
+            // (see 8304878), we assume that the path already in the map is equivalent
+            // to the path we are about to put: hence, no harm if replaced
+            elementToTreePath.put(e, p);
+            return p;
         }
-        return elementToTreePath.computeIfAbsent(e, docTrees::getPath);
     }
 
     /**

test/langtools/jdk/javadoc/doclet/testLatePackageDiscovery/TestLatePackageDiscovery.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2023, 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      8304878
+ * @library  /tools/lib ../../lib
+ * @modules  jdk.javadoc/jdk.javadoc.internal.tool
+ * @build    toolbox.ToolBox javadoc.tester.*
+ * @run main TestLatePackageDiscovery
+ */
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+import javadoc.tester.JavadocTester;
+import toolbox.ToolBox;
+
+public class TestLatePackageDiscovery extends JavadocTester {
+
+    private final ToolBox tb = new ToolBox();
+
+    public static void main(String... args) throws Exception {
+        new TestLatePackageDiscovery().runTests();
+    }
+
+    @Test
+    public void testLatePackageDiscovery(Path base) throws IOException {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src.resolve("test.bar"),
+                "module test.bar { exports bar; }",
+                "package bar;",
+                "package bar; class Base { public void m() { } }",
+                "package bar; public class Bar extends Base { }");
+
+        tb.writeJavaFiles(src.resolve("test.foo"),
+                "module test.foo { exports foo; requires test.bar; }",
+                "package foo;",
+                "package foo; public class Foo extends bar.Bar { }");
+
+        javadoc("-d", base.resolve("out").toString(),
+                "--module-source-path", src.toString(),
+                "--module", "test.foo",
+                "-nodeprecated");
+
+        setAutomaticCheckNoStacktrace(true); // no exceptions!
+        checkExit(Exit.OK);
+    }
+}