gnodet commented on code in PR #11029:
URL: https://github.com/apache/maven/pull/11029#discussion_r3502304978
##########
impl/maven-core/src/main/java/org/apache/maven/classrealm/DefaultClassRealmManager.java:
##########
@@ -364,4 +373,65 @@ private static Object getId(ClassLoader classLoader) {
}
return classLoader;
}
+
+ private static final String MODULE_ACCESS_DESCRIPTOR =
"META-INF/maven/module-access";
+
+ private void applyModuleAccessDescriptors(ClassRealm classRealm) {
Review Comment:
Good question. The direction is your second option:
`META-INF/maven/module-access` opens/exports packages **from** a named module
in the boot/runtime layer **to** the plugin's classloader (which lives in the
unnamed module).
A concrete example: JLine ships as named modules (`org.jline.terminal`,
`org.jline.reader`, etc.) in Maven's `lib/modules/` directory. A plugin running
on the classpath (unnamed module) that needs to interact with JLine's SPI would
include:
```
# META-INF/maven/module-access
add-exports org.jline.terminal/org.jline.terminal.spi=ALL-UNNAMED
add-opens org.jline.terminal/org.jline.terminal.impl=ALL-UNNAMED
```
This is semantically identical to passing `--add-exports
org.jline.terminal/org.jline.terminal.spi=ALL-UNNAMED` on the JVM command line
— it's the standard JPMS mechanism for granting the unnamed module access to
packages from named modules. We just read it from a descriptor instead of
requiring JVM flags.
As for why the standard `module-info` mechanism doesn't work here:
- The plugin doesn't own the module it needs access to (e.g.,
`org.jline.terminal`), so it can't add `exports` to someone else's module
descriptor
- `qualified exports` in `module-info.java` require knowing the target
module name at compile time, but the plugin is on the classpath (unnamed
module, no name to export to)
- The only standard way to do this at runtime is `--add-exports` /
`Module.addExports()` via a `Controller` — which is exactly what the
implementation calls under the hood
You're right that this lets class A decide what's visible inside class B's
module. That's inherent to the problem: plugins need access to packages that
named modules don't export to `ALL-UNNAMED` by default. The same tension exists
with `--add-exports` on the JVM command line. The `module-access` descriptor at
least makes this explicit and declarative — Maven logs a debug message for each
directive applied, so it's auditable.
For modular plugins (the new `<modular>true</modular>` path), this is less
of an issue because the plugin itself is a named module and can use proper
`requires` directives in its own `module-info.java`. The `module-access`
mechanism is primarily needed for classic (classpath-based) plugins that need
to interact with modularized libraries.
##########
impl/maven-classworlds/src/test/java/org/codehaus/plexus/classworlds/realm/ClassRealmImplTest.java:
##########
@@ -0,0 +1,482 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.codehaus.plexus.classworlds.realm;
+
+/*
+ * Copyright 2001-2006 Codehaus Foundation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.codehaus.plexus.classworlds.AbstractClassWorldsTestCase;
+import org.codehaus.plexus.classworlds.ClassWorld;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.fail;
+
+class ClassRealmImplTest extends AbstractClassWorldsTestCase {
+ private ClassWorld world;
+
+ @BeforeEach
+ public void setUp() {
+ this.world = new ClassWorld();
+ }
+
+ @AfterEach
+ public void tearDown() {
+ this.world = null;
+ }
+
+ @Test
+ void testNewRealm() throws Exception {
+ ClassRealm realm = this.world.newRealm("foo");
+
+ assertNotNull(realm);
+
+ assertSame(this.world, realm.getWorld());
+
+ assertEquals("foo", realm.getId());
+ }
+
+ @Test
+ void testLocateSourceRealmNoImports() {
+ ClassRealm realm = new ClassRealm(this.world, "foo", null);
+
+ assertSame(null, realm.getImportClassLoader("com.werken.Stuff"));
+ }
+
+ @Test
+ void testLocateSourceRealmSimpleImport() throws Exception {
+ ClassRealm mainRealm = this.world.newRealm("main");
+
+ ClassRealm werkflowRealm = this.world.newRealm("werkflow");
+
+ mainRealm.importFrom("werkflow", "com.werken.werkflow");
+
+ assertSame(werkflowRealm,
mainRealm.getImportClassLoader("com.werken.werkflow.WerkflowEngine"));
+
Review Comment:
Agreed — these came from the original plexus-classworlds fork. Will clean up.
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