Load extensions from extra classpath

jjava-kernel/pom.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
     <parent>
@@ -30,4 +31,17 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>--add-opens jdk.jshell/jdk.jshell=ALL-UNNAMED</argLine>
+                    <reuseForks>false</reuseForks>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 </project>

jjava-kernel/src/main/java/org/dflib/jjava/kernel/JavaKernel.java

@@ -76,6 +76,7 @@ protected JavaKernel(
             MagicParser magicParser,
             MagicsRegistry magicsRegistry,
             ExtensionLoader extensionLoader,
+            String extraClasspath,
             boolean extensionsEnabled,
             StringStyler errorStyler,
             JShell jShell,
@@ -101,6 +102,9 @@ protected JavaKernel(
 
         if (extensionsEnabled) {
             this.extensionLoader.loadFromDefaultClasspath().forEach(e -> e.install(this));
+            if (extraClasspath != null) {
+                this.extensionLoader.loadFromClasspath(extraClasspath).forEach(e -> e.install(this));
+            }
         }
     }
 
@@ -383,6 +387,7 @@ public JavaKernel build() {
                     buildMagicParser(magicTranspiler),
                     buildMagicsRegistry(),
                     buildExtensionLoader(),
+                    buildExtraClasspath(),
                     buildExtensionsEnabled(),
                     buildErrorStyler(),
                     jShell,
@@ -396,5 +401,9 @@ protected List<HelpLink> buildHelpLinks() {
                     new HelpLink("JJava homepage", "https://github.com/dflib/jjava")
             );
         }
+
+        private String buildExtraClasspath() {
+            return extraClasspath;
+        }
     }
 }

jjava-kernel/src/test/java/org/dflib/jjava/kernel/ExtensionLoadingBuiltInTest.java

@@ -0,0 +1,14 @@
+package org.dflib.jjava.kernel;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class ExtensionLoadingBuiltInTest {
+
+    @Test
+    void loadsExtensionsFromInitialClasspath() {
+        JavaKernel.builder().name("TestKernel").build();
+        assertNotNull(JavaNotebookStatics.kernel(), "Built-in extension should be installed from initial classpath");
+    }
+}

jjava-kernel/src/test/java/org/dflib/jjava/kernel/ExtensionLoadingExtraClasspathTest.java

@@ -0,0 +1,36 @@
+package org.dflib.jjava.kernel;
+
+import org.dflib.jjava.jupyter.kernel.util.PathsHandler;
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ExtensionLoadingExtraClasspathTest {
+
+    @Test
+    void loadsExtensionsFromExtraClasspath() throws Exception {
+        Path jar = TestJarFactory.buildJar(
+                "java/",
+                "java/org/dflib/jjava/kernel/test/TestExtension.java",
+                "java/META-INF/services/org.dflib.jjava.jupyter.Extension"
+        );
+
+        String extraClasspath = PathsHandler.joinPaths(PathsHandler.resolveGlobs(jar.toAbsolutePath().toString()));
+
+        String extensionClassName = "org.dflib.jjava.kernel.test.TestExtension";
+        String installationsProperty = extensionInstallationsProperty(extensionClassName);
+        System.clearProperty(installationsProperty);
+
+        JavaKernel kernel = JavaKernel.builder().name("TestKernel").extraClasspath(extraClasspath).build();
+        assertEquals("1", System.getProperty(installationsProperty));
+
+        kernel.addToClasspath(extraClasspath);
+        assertEquals("1", System.getProperty(installationsProperty));
+    }
+
+    private static String extensionInstallationsProperty(String className) {
+        return "ext.installs:" + className;
+    }
+}

jjava-kernel/src/test/java/org/dflib/jjava/kernel/TestJarFactory.java

@@ -0,0 +1,119 @@
+package org.dflib.jjava.kernel;
+
+import javax.tools.DiagnosticCollector;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.StandardLocation;
+import javax.tools.ToolProvider;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.jar.JarEntry;
+import java.util.jar.JarOutputStream;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+final class TestJarFactory {
+
+    private static final Map<Set<String>, Path> cache = new HashMap<>();
+
+    private TestJarFactory() {
+    }
+
+    static synchronized Path buildJar(String prefix, String... resourcePaths) throws Exception {
+        Set<String> cacheKey = Set.of(resourcePaths);
+        if (cache.containsKey(cacheKey)) {
+            Path cached = cache.get(cacheKey);
+            if (Files.exists(cached)) {
+                return cached;
+            }
+        }
+
+        Path tmpDir = Files.createTempDirectory("jjava-test-jar-");
+        Path srcDir = tmpDir.resolve("src");
+        Path classesDir = tmpDir.resolve("classes");
+        Files.createDirectories(srcDir);
+        Files.createDirectories(classesDir);
+
+        moveResources(prefix, resourcePaths, srcDir, classesDir);
+        compileJava(srcDir, classesDir);
+        Path jar = packageJar(tmpDir.resolve("test.jar"), classesDir);
+
+        cache.put(cacheKey, jar);
+        return jar;
+    }
+
+    private static void moveResources(String prefix, String[] resourcePaths, Path srcDir, Path classesDir) throws IOException {
+        for (String resourcePath : resourcePaths) {
+            URL url = TestJarFactory.class.getResource("/" + resourcePath);
+            if (url == null) {
+                throw new IllegalArgumentException("Resource not found: " + resourcePath);
+            }
+
+            String targetRelativePath = resourcePath;
+            if (prefix != null && !prefix.isEmpty() && resourcePath.startsWith(prefix)) {
+                targetRelativePath = resourcePath.substring(prefix.length());
+            }
+
+            Path targetDir = resourcePath.endsWith(".java") ? srcDir : classesDir;
+            Path targetPath = targetDir.resolve(targetRelativePath);
+            Files.createDirectories(targetPath.getParent());
+            try (InputStream in = url.openStream()) {
+                Files.copy(in, targetPath, StandardCopyOption.REPLACE_EXISTING);
+            }
+        }
+    }
+
+    private static void compileJava(Path srcDir, Path classesDir) throws IOException {
+        List<File> srcFiles;
+        try (Stream<Path> stream = Files.walk(srcDir)) {
+            srcFiles = stream.filter(Files::isRegularFile).map(Path::toFile).collect(Collectors.toList());
+        }
+        if (srcFiles.isEmpty()) {
+            return;
+        }
+
+        JavaCompiler compiler = Objects.requireNonNull(ToolProvider.getSystemJavaCompiler());
+        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
+        try (StandardJavaFileManager fm = compiler.getStandardFileManager(diagnostics, null, null)) {
+            fm.setLocation(StandardLocation.CLASS_OUTPUT, List.of(classesDir.toFile()));
+            Iterable<? extends JavaFileObject> units = fm.getJavaFileObjectsFromFiles(srcFiles);
+            Boolean ok = compiler.getTask(null, fm, diagnostics, null, null, units).call();
+            if (!Boolean.TRUE.equals(ok)) {
+                throw new IllegalStateException("Compilation failed: " + diagnostics.getDiagnostics());
+            }
+        }
+    }
+
+    private static Path packageJar(Path jarPath, Path classesDir) throws IOException {
+        try (JarOutputStream jos = new JarOutputStream(Files.newOutputStream(jarPath))) {
+            writeDirToJar(jos, classesDir, classesDir);
+        }
+        return jarPath;
+    }
+
+    private static void writeDirToJar(JarOutputStream jos, Path root, Path dir) throws IOException {
+        try (Stream<Path> stream = Files.walk(dir)) {
+            for (Path path : (Iterable<Path>) stream::iterator) {
+                if (Files.isDirectory(path)) {
+                    continue;
+                }
+                String entryName = root.relativize(path).toString().replace('\\', '/');
+                JarEntry entry = new JarEntry(entryName);
+                jos.putNextEntry(entry);
+                Files.copy(path, jos);
+                jos.closeEntry();
+            }
+        }
+    }
+}

jjava-kernel/src/test/resources/java/META-INF/services/org.dflib.jjava.jupyter.Extension

@@ -0,0 +1 @@
+org.dflib.jjava.kernel.test.TestExtension

jjava-kernel/src/test/resources/java/org/dflib/jjava/kernel/test/TestExtension.java

@@ -0,0 +1,19 @@
+package org.dflib.jjava.kernel.test;
+
+import org.dflib.jjava.jupyter.Extension;
+import org.dflib.jjava.jupyter.kernel.BaseKernel;
+
+public class TestExtension implements Extension {
+
+    @Override
+    public void install(BaseKernel kernel) {
+        String key = "ext.installs:" + getClass().getName();
+        String value = System.getProperty(key, "0");
+        try {
+            int count = Integer.parseInt(value);
+            System.setProperty(key, String.valueOf(count + 1));
+        } catch (NumberFormatException e) {
+            System.setProperty(key, "1");
+        }
+    }
+}