8298727: Trees.getPath may crash for unnamed package

Reviewed-by: vromero

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Enter.java

@@ -356,10 +356,12 @@ public class Enter extends JCTree.Visitor {
             tree.packge.complete(); // Find all classes in package.
 
             Env<AttrContext> topEnv = topLevelEnv(tree);
-            Env<AttrContext> packageEnv = isPkgInfo ? topEnv.dup(pd) : null;
+            Env<AttrContext> packageEnv = null;
 
             // Save environment of package-info.java file.
             if (isPkgInfo) {
+                packageEnv = topEnv.dup(pd != null ? pd : tree);
+
                 Env<AttrContext> env0 = typeEnvs.get(tree.packge);
                 if (env0 != null) {
                     JCCompilationUnit tree0 = env0.toplevel;

test/langtools/tools/javac/processing/model/EmptyPackageInfo.java

@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2022, 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 8298727
+ * @summary Verify empty package-info.java is handled properly
+ * @library /tools/lib
+ * @modules jdk.compiler/com.sun.tools.javac.api
+ *          jdk.compiler/com.sun.tools.javac.main
+ * @build toolbox.TestRunner toolbox.ToolBox EmptyPackageInfo
+ * @run main EmptyPackageInfo
+ */
+
+import com.sun.source.tree.Tree;
+import com.sun.source.util.JavacTask;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import com.sun.source.util.Trees;
+import java.util.ArrayList;
+import java.util.List;
+import javax.tools.ToolProvider;
+import toolbox.TestRunner;
+import toolbox.TestRunner.Test;
+import toolbox.ToolBox;
+
+public class EmptyPackageInfo extends TestRunner {
+
+    public static void main(String... args) throws Exception {
+        new EmptyPackageInfo().runTests(m -> new Object[] { Paths.get(m.getName()) });
+    }
+
+    private final ToolBox tb = new ToolBox();
+
+    public EmptyPackageInfo() {
+        super(System.err);
+    }
+
+    @Test
+    public void testEmptyPackageInfo(Path outerBase) throws Exception {
+        Path src = outerBase.resolve("src");
+        Path classes = outerBase.resolve("classes");
+        Path packInfo = src.resolve("package-info.java");
+
+        tb.writeFile(packInfo, "/**javadoc*/\n");
+        Files.createDirectories(classes);
+
+        var compiler = ToolProvider.getSystemJavaCompiler();
+
+        try (var fm = compiler.getStandardFileManager(null,
+                                                      null,
+                                                      null)) {
+            var task =
+                    (JavacTask) compiler.getTask(null,
+                                                 fm,
+                                                 null,
+                                                 null,
+                                                 null,
+                                                 fm.getJavaFileObjects(packInfo));
+            task.analyze();
+            var pack = task.getElements().getPackageElement("");
+            var trees = Trees.instance(task);
+            var packPath = trees.getPath(pack);
+            var packTree = packPath.getLeaf();
+            if (packTree.getKind() != Tree.Kind.COMPILATION_UNIT) {
+                throw new AssertionError("Unexpected tree kind: " + packTree.getKind());
+            }
+            var actualJavadoc = trees.getDocComment(packPath);
+            var expectedJavadoc = "javadoc";
+            if (!expectedJavadoc.equals(actualJavadoc)) {
+                throw new AssertionError("Unexpected javadoc, " +
+                                         "expected: " + expectedJavadoc +
+                                         ", got: " + actualJavadoc);
+            }
+        }
+    }
+
+    @Test
+    public void testMultipleFiles(Path outerBase) throws Exception {
+        Path src = outerBase.resolve("src");
+        Path classes = outerBase.resolve("classes");
+        Path packInfo1 = src.resolve("test1").resolve("package-info.java");
+        Path packInfo2 = src.resolve("test2").resolve("package-info.java");
+
+        tb.writeFile(packInfo1, "");
+        tb.writeFile(packInfo2, "");
+        Files.createDirectories(classes);
+
+        var compiler = ToolProvider.getSystemJavaCompiler();
+
+        try (var fm = compiler.getStandardFileManager(null,
+                                                      null,
+                                                      null)) {
+            var diags = new ArrayList<String>();
+            var task =
+                    (JavacTask) compiler.getTask(null,
+                                                 fm,
+                                                 d -> diags.add(d.getCode()),
+                                                 null,
+                                                 null,
+                                                 fm.getJavaFileObjects(packInfo1,
+                                                                       packInfo2));
+            task.analyze();
+            var expectedDiags =
+                    List.of("compiler.warn.pkg-info.already.seen");
+            if (!expectedDiags.equals(diags)) {
+                throw new AssertionError("Unexpected diags, " +
+                                         "expected: " + expectedDiags +
+                                         ", got: " + diags);
+            }
+        }
+    }
+}