Starting the LSP server locally inside the JVM (second take)

.gitignore

@@ -1,4 +1,36 @@
-.settings
-/bin
-/.project
-target
+build/
+.out/
+bin/
+.bin/
+target/
+
+/gradle.properties
+/archive/
+/META-INF
+
+.classpath
+.project
+.settings
+
+.idea/
+*.iml
+*.iws
+*.ipr
+.idea_modules/
+**/out/
+
+*.tmp
+*.bak
+*.swp
+*~
+
+.gradle
+
+.DS_Store*
+.AppleDouble
+.LSOverride
+
+.directory
+.Trash*
+
+**/adhoctest/

README.md

@@ -41,3 +41,17 @@ Once https://github.com/mickaelistria/eclipse-bluesky/issues/63 will work in Pho
 
 HTML syntax coloration (managed with TextMate) and HTML completion, mark occurrences, etc is not a part of this plugin. I suggest you that you install https://github.com/mickaelistria/eclipse-bluesky
 which provides those features.
+
+Development in Eclipse
+======================
+
+1. Use "Eclipse for Committers" (Photon M6 as of this writing).
+
+2. In Eclipse, "File" / "Import..." / "Existing Maven Projects". Point at the `lsp4e-freemarker` project root directory, add all the Maven projects it finds.
+
+3. Now go to "Window" / "Preferences" / "Plug-in Development" / "Target Platform", and Select "lsp4e-freemarker" (this only appears if you have imported the "target-platform" Maven project earlier).
+   After this, there shouldn't be more errors in the project (no dependency classes that aren't found).
+
+4. To try the plugin, right click on the `org.eclipse.lsp4j.freemarker` project, then "Run as" / "Eclipse Application".
+   (TODO: Currently that will fail with `Application "org.eclipse.ui.ide.workbench" could not be found in the registry`. I have worked that around by adding 
+   `<location path="${eclipse_home}" type="Directory"/>` to the target platform, but of course there must be a better way.)

org.eclipse.lsp4e.freemarker/META-INF/MANIFEST.MF

@@ -14,8 +14,7 @@ Require-Bundle: org.eclipse.lsp4e,
  org.eclipse.jface,
  org.eclipse.ui.workbench.texteditor,
  org.eclipse.ui.editors,
- org.eclipse.ui.genericeditor,
- org.eclipse.jdt.launching
+ org.eclipse.ui.genericeditor
 Bundle-Activator: org.eclipse.lsp4e.freemarker.FreemarkerPlugin
 Bundle-ActivationPolicy: lazy
 Eclipse-BundleShape: dir

org.eclipse.lsp4e.freemarker/plugin.xml

@@ -34,7 +34,7 @@
    <extension
          point="org.eclipse.lsp4e.languageServer">
       <server
-            class="org.eclipse.lsp4e.freemarker.FreemarkerLanguageServer"
+            class="org.eclipse.lsp4e.freemarker.FreemarkerStreamConnectionProvider"
             id="org.eclipse.lsp4e.freemarker"
             label="Freemarker Language Server" >
       </server>

org.eclipse.lsp4e.freemarker/src/org/eclipse/lsp4e/freemarker/FreemarkerStreamConnectionProvider.java

@@ -0,0 +1,95 @@
+/**
+ *  Copyright (c) 2018 Angelo ZERR, Daniel Dekany.
+ *  All rights reserved. This program and the accompanying materials
+ *  are made available under the terms of the Eclipse Public License v1.0
+ *  which accompanies this distribution, and is available at
+ *  http://www.eclipse.org/legal/epl-v10.html
+ *
+ *  Contributors:
+ *  Angelo Zerr <[email protected]> - initial API and implementation
+ */
+package org.eclipse.lsp4e.freemarker;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Arrays;
+import java.util.concurrent.Future;
+
+import org.eclipse.core.runtime.Platform;
+import org.osgi.framework.Bundle;
+
+/**
+ * Starts the FreeMarker LSP server inside the current JVM, and connects to it.
+ */
+public class FreemarkerStreamConnectionProvider extends LocalStreamConnectionProvider {
+
+	public FreemarkerStreamConnectionProvider() {
+		super(FreemarkerPlugin.getDefault().getLog(), FreemarkerPlugin.getPluginId());
+	}
+
+	private static final String LANGUAGE_SERVER_JAR_ENTRY_NAME = "server/freemarker-languageserver-all.jar"; //$NON-NLS-1$
+	private static final String LANGUAGE_SERVER_LAUNCHER_CLASS_NAME = "freemarker.ext.languageserver.FreemarkerServerLauncher"; //$NON-NLS-1$
+
+	@Override
+	protected LocalServer launchServer(InputStream clientToServerStream, OutputStream serverToClientStream)
+			throws IOException {
+		URL[] classPath = getFreemarkerLanguageServerClassPath();
+		logInfo("Using class path: " + Arrays.toString(classPath));
+
+		URLClassLoader dynamicJarClassLoader = new URLClassLoader(classPath);
+
+		Method launcherMethod;
+		try {
+			Class<?> launcherClass = dynamicJarClassLoader.loadClass(LANGUAGE_SERVER_LAUNCHER_CLASS_NAME);
+			launcherMethod = launcherClass.getMethod("launch", //$NON-NLS-1$
+					new Class<?>[] { InputStream.class, OutputStream.class });
+		} catch (Exception e) {
+			throw new RuntimeException(
+					"Couldn't get launcher class and method via Java reflection (using class path: "
+					+ Arrays.toString(classPath) + "); see cause exception", e); //$NON-NLS-2$
+		}
+		Future<?> launchedFuture;
+		try {
+			launchedFuture = (Future<?>) launcherMethod.invoke(null, clientToServerStream, serverToClientStream);
+		} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
+			throw new RuntimeException("Error when calling launcher method; see cause exception", e); //$NON-NLS-1$
+		}
+
+		return new LocalServer(launchedFuture) {
+			@Override
+			public void stop() {
+				super.stop();
+				try {
+					dynamicJarClassLoader.close();
+				} catch (IOException e) {
+					logError("Error when closing the dynamic jar class-loader", e); //$NON-NLS-1$
+				}
+			}
+		};
+	}
+
+	private URL[] getFreemarkerLanguageServerClassPath() {
+		Bundle bundle = Platform.getBundle(FreemarkerPlugin.PLUGIN_ID);
+		if (bundle == null) {
+			throw new RuntimeException("Bundle " + FreemarkerPlugin.PLUGIN_ID + " not found"); //$NON-NLS-1$
+		}
+
+		URL languageServerJarURL = bundle.getEntry(LANGUAGE_SERVER_JAR_ENTRY_NAME);
+		if (languageServerJarURL == null) {
+			throw new RuntimeException(
+					"Entity " + LANGUAGE_SERVER_JAR_ENTRY_NAME + " not found in bundle " + FreemarkerPlugin.PLUGIN_ID); //$NON-NLS-1$
+		}
+
+		// TODO: Add freemarker.jar from the user project here, if it's found and has
+		// high enough version, otherwise add freemarker.jar from this plugin.
+		// (Currently, freemarker.jar is bundled into the language server jar.)
+
+		return new URL[] { languageServerJarURL };
+	}
+
+}