8372787: ModuleReader should throw IOException consistently when using --patch-module and ModuleReader is closed

Reviewed-by: alanb

src/java.base/share/classes/jdk/internal/module/ModulePatcher.java

@@ -225,6 +225,7 @@ public final class ModulePatcher {
         private final ModuleReference mref;
         private final URL delegateCodeSourceURL;
         private volatile ModuleReader delegate;
+        private volatile boolean closed;
 
         /**
          * Creates the ModuleReader to reads resources in a patched module.
@@ -291,6 +292,15 @@ public final class ModulePatcher {
             return r;
         }
 
+        /**
+         * Throws an IOException if the ModuleReader is closed.
+         */
+        private void ensureOpen() throws IOException {
+            if (closed) {
+                throw new IOException("ModuleReader is closed");
+            }
+        }
+
         /**
          * Finds a resources in the patch locations. Returns null if not found
          * or the name is "module-info.class" as that cannot be overridden.
@@ -310,7 +320,7 @@ public final class ModulePatcher {
          * Finds a resource of the given name in the patched module.
          */
         public Resource findResource(String name) throws IOException {
-
+            assert !closed : "module reader is closed";
             // patch locations
             Resource r = findResourceInPatch(name);
             if (r != null)
@@ -354,6 +364,7 @@ public final class ModulePatcher {
 
         @Override
         public Optional<URI> find(String name) throws IOException {
+            ensureOpen();
             Resource r = findResourceInPatch(name);
             if (r != null) {
                 URI uri = URI.create(r.getURL().toString());
@@ -365,6 +376,7 @@ public final class ModulePatcher {
 
         @Override
         public Optional<InputStream> open(String name) throws IOException {
+            ensureOpen();
             Resource r = findResourceInPatch(name);
             if (r != null) {
                 return Optional.of(r.getInputStream());
@@ -375,6 +387,7 @@ public final class ModulePatcher {
 
         @Override
         public Optional<ByteBuffer> read(String name) throws IOException {
+            ensureOpen();
             Resource r = findResourceInPatch(name);
             if (r != null) {
                 ByteBuffer bb = r.getByteBuffer();
@@ -398,6 +411,7 @@ public final class ModulePatcher {
 
         @Override
         public Stream<String> list() throws IOException {
+            ensureOpen();
             Stream<String> s = delegate().list();
             for (ResourceFinder finder : finders) {
                 s = Stream.concat(s, finder.list());
@@ -407,6 +421,10 @@ public final class ModulePatcher {
 
         @Override
         public void close() throws IOException {
+            if (closed) {
+                return;
+            }
+            closed = true;
             closeAll(finders);
             delegate().close();
         }

test/jdk/java/lang/module/ModuleReader/patched/PatchedModuleReaderTest.java

@@ -0,0 +1,132 @@
+/*
+ * 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.
+ *
+ * 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.
+ */
+
+import java.io.IOException;
+import java.lang.module.ModuleFinder;
+import java.lang.module.ModuleReader;
+import java.lang.module.ModuleReference;
+import java.net.URI;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/*
+ * @test
+ * @bug 8372787
+ * @summary Test the behaviour of ModuleReader when using --patch-module
+ * @comment patch the java.base module with a test specific resource
+ * @compile/module=java.base java/lang/PatchedFoo.java
+ * @run junit/othervm ${test.main.class}
+ */
+class PatchedModuleReaderTest {
+
+    private static ModuleReference patchedModuleRef;
+
+    @BeforeAll
+    static void beforeAll() {
+        patchedModuleRef = ModuleFinder.ofSystem()
+                .find("java.base")
+                .orElseThrow();
+    }
+
+    /*
+     * Verifies that the resource that was patched into a module
+     * is found by the ModuleReader.
+     */
+    @Test
+    void testResourceFound() throws Exception {
+        try (ModuleReader reader = patchedModuleRef.open()) {
+            String resourceName = "java/lang/PatchedFoo.class";
+            Optional<URI> res = reader.find(resourceName);
+            assertTrue(res.isPresent(), resourceName + " is missing in "
+                    + patchedModuleRef.descriptor().name() + " module");
+            URI uri = res.get();
+            assertEquals("file", uri.getScheme(),
+                    "unexpected scheme in resource URI " + uri);
+            assertTrue(uri.getPath().endsWith(resourceName),
+                    "unexpected path component " + uri.getPath()
+                            + " in resource URI " + uri);
+
+        }
+    }
+
+    /*
+     * Verifies the ModuleReader against a resource which isn't
+     * expected to be part of the patched module.
+     */
+    @Test
+    void testResourceNotFound() throws Exception {
+        try (ModuleReader reader = patchedModuleRef.open()) {
+            String nonExistentResource = "foo/bar/NonExistent.class";
+            Optional<URI> res = reader.find(nonExistentResource);
+            assertTrue(res.isEmpty(), "unexpected resource " + nonExistentResource
+                    + " in " + patchedModuleRef.descriptor().name() + " module");
+        }
+    }
+
+    /*
+     * This test opens a ModuleReader for a patched module, accumulates
+     * the Stream of resources from that ModuleReader and then closes that
+     * ModuleReader. It then verifies that the closed ModuleReader
+     * throws the specified IOException whenever it is used for subsequent
+     * operations on the Stream of resources.
+     */
+    @Test
+    void testIOExceptionAfterClose() throws Exception {
+        ModuleReader reader;
+        Stream<String> resources;
+        try (var _ = reader = patchedModuleRef.open()) {
+            // hold on to the available resources, to test them after the
+            // ModuleReader is closed
+            resources = reader.list();
+        } // close the ModuleReader
+
+        // verify IOException is thrown by the closed ModuleReader
+
+        assertThrows(IOException.class, () -> reader.list(),
+                "ModuleReader.list()");
+
+        resources.forEach(rn -> {
+            assertThrows(IOException.class, () -> reader.read(rn),
+                    "ModuleReader.read(String)");
+            assertThrows(IOException.class, () -> reader.open(rn),
+                    "ModuleReader.open(String)");
+            assertThrows(IOException.class, () -> reader.find(rn),
+                    "ModuleReader.find(String)");
+        });
+
+        // repeat the test for a non-existent resource
+        String nonExistentResource = "foo/bar/NonExistent.class";
+        assertThrows(IOException.class, () -> reader.read(nonExistentResource),
+                "ModuleReader.read(String)");
+        assertThrows(IOException.class, () -> reader.open(nonExistentResource),
+                "ModuleReader.open(String)");
+        assertThrows(IOException.class, () -> reader.find(nonExistentResource),
+                "ModuleReader.find(String)");
+    }
+}

test/jdk/java/lang/module/ModuleReader/patched/java.base/java/lang/PatchedFoo.java

@@ -0,0 +1,26 @@
+/*
+ * 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.
+ *
+ * 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 java.lang;
+
+public class PatchedFoo {
+}