8299627: Fix/improve handling of "missing" element-list file

Reviewed-by: hannesw

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/resources/doclets.properties

@@ -252,6 +252,7 @@ doclet.linkMismatch_PackagedLinkedtoModule=The code being documented uses packag
 doclet.linkMismatch_ModuleLinkedtoPackage=The code being documented uses modules but the packages defined \
   in {0} are in the unnamed module.
 doclet.urlRedirected=URL {0} was redirected to {1} -- Update the command-line options to suppress this warning.
+doclet.unexpectedRedirect=Unexpected redirection for URL {0} to {1}
 doclet.duplicate.comment.for.property=Duplicate comment for property.\n\
   Remove the comment on the property field or on this method to suppress this warning.
 

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

@@ -668,13 +668,24 @@ public class Extern {
         } while (redir);
 
         if (!url.equals(conn.getURL())) {
-            configuration.getReporter().print(Kind.WARNING,
+            if (!getLastPathComponent(conn.getURL()).equals(getLastPathComponent(url))) {
-                    resources.getText("doclet.urlRedirected", url, conn.getURL()));
+                configuration.getReporter().print(Kind.ERROR,
+                        resources.getText("doclet.unexpectedRedirect", url, conn.getURL()));
+            } else {
+                configuration.getReporter().print(Kind.WARNING,
+                        resources.getText("doclet.urlRedirected", url, conn.getURL()));
+            }
         }
 
         return in;
     }
 
+    private String getLastPathComponent(URL u) {
+        var path = u.getPath();
+        var sep = path.lastIndexOf('/');
+        return sep == -1 ? path : path.substring(sep + 1);
+    }
+
     private void printModularityMismatchDiagnostic(String key, Object arg) {
         switch (configuration.getOptions().linkModularityMismatch()) {
             case INFO -> configuration.getMessages().notice(key, arg);

test/langtools/jdk/javadoc/tool/testExternRedirects/TestExternRedirects.java

@@ -0,0 +1,179 @@
+/*
+ * 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     8299627
+ * @summary Fix/improve handling of "missing" element-list file
+ * @library /tools/lib ../../lib
+ * @modules jdk.javadoc/jdk.javadoc.internal.tool
+ * @build   toolbox.ToolBox javadoc.tester.*
+ * @run main TestExternRedirects
+ */
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
+import java.net.MalformedURLException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.Path;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import com.sun.net.httpserver.HttpServer;
+import javadoc.tester.JavadocTester;
+import toolbox.ToolBox;
+
+public class TestExternRedirects extends JavadocTester {
+    public static void main(String... args) throws Exception {
+        var tester = new TestExternRedirects();
+        tester.runTests();
+    }
+
+    private final ToolBox tb = new ToolBox();
+    private HttpServer httpServer;
+
+    @Override
+    public void runTests() throws Exception {
+        httpServer = startServer();
+        var address = httpServer.getAddress();
+        out.println("server running at " + address);
+        try {
+            super.runTests();
+        } finally {
+            httpServer.stop(0);
+        }
+    }
+
+    private HttpServer startServer() throws IOException {
+        HttpServer server = HttpServer.create(new InetSocketAddress("localhost", 0), 0);
+        server.createContext("/docs", new MyHandler());
+        server.setExecutor(null); // creates a default executor
+        server.start();
+        return server;
+    }
+
+    private class MyHandler implements HttpHandler {
+        @Override
+        public void handle(HttpExchange t) throws IOException {
+            out.println("MyHandler: " + t.getRequestMethod() + " " + t.getRequestURI());
+            assert t.getRequestMethod().equals("GET");
+            var uriPath = t.getRequestURI().getPath();
+            if (uriPath.contains("no-redirect")) {
+                respond(t, HttpURLConnection.HTTP_OK, "");
+            } else if (uriPath.matches(".*/redirect-[1-9]/.*")) {
+                Matcher m = Pattern.compile("redirect-([1-9])").matcher(uriPath);
+                if (m.find()) {
+                    var count = Integer.parseInt(m.group(1));
+                    var u = t.getRequestURI().toString();
+                    var u2 = u.replace("redirect-" + count,
+                            (count == 1) ? "no-redirect" : "redirect-" + (count - 1));
+                    t.getResponseHeaders().add("Location", u2);
+                    respond(t, HttpURLConnection.HTTP_MOVED_PERM, "");
+                } else {
+                    throw new IOException("internal error");
+                }
+            } else if (uriPath.contains("bad-redirect")){
+                var u = t.getRequestURI().toString();
+                var u2 = u.replace("bad-redirect", "no-redirect")
+                                .replaceAll("[^/]+-list$", "not-found.html");
+                t.getResponseHeaders().add("Location", u2);
+                respond(t, HttpURLConnection.HTTP_MOVED_PERM, "");
+            } else {
+                respond(t, HttpURLConnection.HTTP_NOT_FOUND, "");
+            }
+        }
+    }
+
+    private void respond(HttpExchange t, int code, String body) throws IOException {
+        out.println("  respond: " + code);
+        t.getResponseHeaders().forEach((k, v) -> out.println("  header: " + k + ": " + v));
+        body.lines().map(l -> "  body " + l).forEach(out::println);
+
+        t.sendResponseHeaders(code, body.length());
+        try (var os = t.getResponseBody()) {
+            os.write(body.getBytes());
+        }
+    }
+
+    @Test
+    public void testNoRedirect(Path base) throws Exception {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, "package p; public class C { }");
+
+        javadoc("-d", base.resolve("api").toString(),
+                "-sourcepath", src.toString(),
+                "-Xdoclint:none",
+                "-link", getURL("no-redirect").toString(),
+                "p");
+        checkExit(Exit.OK);
+    }
+
+    @Test
+    public void testSomeRedirect(Path base) throws Exception {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, "package p; public class C { }");
+
+        javadoc("-d", base.resolve("api").toString(),
+                "-sourcepath", src.toString(),
+                "-Xdoclint:none",
+                "-link", getURL("redirect-3").toString(),
+                "p");
+        checkExit(Exit.OK);
+
+        new OutputChecker(Output.OUT)
+                .check(Pattern.compile("warning: URL .*/docs/redirect-3/element-list" +
+                        " was redirected to .*/docs/no-redirect/element-list"));
+    }
+
+    @Test
+    public void testBadRedirect(Path base) throws Exception {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, "package p; public class C { }");
+
+        javadoc("-d", base.resolve("api").toString(),
+                "-sourcepath", src.toString(),
+                "-Xdoclint:none",
+                "-link", getURL("bad-redirect").toString(),
+                "p");
+        checkExit(Exit.ERROR);
+
+        checkOutput(Output.OUT, true,
+                "error: Unexpected redirection for URL");
+    }
+
+    private URL getURL(String key) throws URISyntaxException, MalformedURLException {
+        return new URI("http",
+                null,  // user-info
+                httpServer.getAddress().getHostName(),
+                httpServer.getAddress().getPort(),
+                "/docs/" + key,
+                null, // query
+                null // fragment
+                ).toURL();
+    }
+}