fixes issues with shutting down when vs-code extension process stops

ls/service/src/main/java/org/opencds/cqf/cql/ls/service/Main.java

@@ -2,6 +2,9 @@
 
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.LoggerContext;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import org.cqframework.cql.cql2elm.CqlTranslator;
 import org.eclipse.lsp4j.jsonrpc.Launcher;
@@ -18,7 +21,19 @@
 import org.springframework.context.annotation.Import;
 
 /**
- * This class starts a CqlLanguageServer running as a service listening on std-in/std-out
+ * Main entry point for the CQL Language Server service.
+ * <p>
+ * This class starts a CqlLanguageServer running as a service that communicates
+ * via the Language Server Protocol (LSP) over stdin/stdout. It is designed to be
+ * launched by LSP clients such as VS Code extensions.
+ * <p>
+ * Key behaviors:
+ * <ul>
+ *   <li>Runs as a Spring Boot CommandLineRunner (non-web application)</li>
+ *   <li>Logs to stderr to keep stdout clear for LSP communication</li>
+ *   <li>Monitors both exit() notifications and connection closure for shutdown</li>
+ *   <li>Terminates the JVM with System.exit(0) when the connection closes</li>
+ * </ul>
  */
 @Import(ServerConfig.class)
 public class Main implements CommandLineRunner {
@@ -39,15 +54,26 @@ public static void main(String[] args) {
     CqlLanguageServer server;
 
     @Override
-    public void run(String... args) throws Exception {
+    public void run(String... args) {
         @SuppressWarnings("java:S106")
         Launcher<LanguageClient> launcher = LSPLauncher.createServerLauncher(server, System.in, System.out);
 
         LanguageClient client = launcher.getRemoteProxy();
-        // We actually connect to the process std-err on the client side for logging.
-        // We could change that and append to the client's logMessage API from the
-        // server-side instead.
+
+        // Logging Strategy:
+        // Currently logs are written to stderr (configured in logback.xml).
+        // The client can capture stderr and display it separately.
+        //
+        // Alternative: Send logs to the client's LSP window/logMessage API
+        // by uncommenting the line below. This would show logs in VS Code's
+        // Output panel for the language server channel.
+        //
+        // Trade-offs:
+        // - stderr: Simpler, works with any LSP client, easier to redirect to files
+        // - client API: Integrated into IDE, automatic log level filtering in UI
+        //
         // setupClientAppender(client);
+
         server.connect(client);
         Future<Void> serverThread = launcher.startListening();
 
@@ -60,15 +86,78 @@ public void run(String... args) throws Exception {
 
         log.info("cql-language-server started");
 
-        server.exited().get();
+        // Shutdown Strategy:
+        // Monitor two conditions in parallel to handle both normal and abnormal shutdowns:
+        // 1. server.exited() - Completes when LSP exit() notification is received (normal shutdown)
+        // 2. connectionClosed - Completes when stdin/stdout closes (client disconnect/crash)
+        //
+        // We wait for whichever happens first. This ensures the server terminates properly
+        // when VS Code closes, even if the exit() notification never arrives.
+
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        CompletableFuture<Void> connectionClosed = CompletableFuture.runAsync(
+                () -> {
+                    try {
+                        // This blocks until the LSP connection closes (stdin/stdout closed)
+                        serverThread.get();
+                        log.info("LSP connection closed");
+                    } catch (Exception e) {
+                        log.debug("Server thread exception", e);
+                    }
+                },
+                executor);
+
+        // Wait for whichever completes first: exit() or connection closure
+        try {
+            CompletableFuture.anyOf(server.exited(), connectionClosed).get();
+        } catch (Exception e) {
+            log.error("Error waiting for shutdown", e);
+        }
+
+        log.info("Shutting down language server");
         serverThread.cancel(true);
+        executor.shutdownNow();
+
+        // Force JVM termination to ensure all threads (including Spring-managed ones) are stopped.
+        // Using System.exit(0) is necessary because Spring Boot may have non-daemon threads running.
+        System.exit(0);
     }
 
+    /**
+     * Configures SLF4J logging bridge to redirect java.util.logging to SLF4J.
+     * This ensures all logging from third-party libraries flows through our
+     * configured Logback appenders (currently configured to write to stderr).
+     */
     public static void configureLogging() {
         SLF4JBridgeHandler.removeHandlersForRootLogger();
         SLF4JBridgeHandler.install();
     }
 
+    /**
+     * Alternative logging approach: Send logs to the LSP client via window/logMessage.
+     * <p>
+     * When enabled, this appender sends all log messages to the language client's
+     * logMessage API, which displays them in the IDE's Output panel for the
+     * language server channel.
+     * <p>
+     * Benefits:
+     * <ul>
+     *   <li>Logs appear directly in VS Code's Output panel</li>
+     *   <li>IDE provides UI controls for filtering log levels</li>
+     *   <li>No need to configure separate stderr capture</li>
+     * </ul>
+     * <p>
+     * Drawbacks:
+     * <ul>
+     *   <li>Logs can't be easily redirected to files</li>
+     *   <li>May clutter the client connection with high-volume logging</li>
+     *   <li>Dependent on client implementation of window/logMessage</li>
+     * </ul>
+     * <p>
+     * To enable: Uncomment the setupClientAppender(client) call on line 63.
+     *
+     * @param client The LSP language client to send log messages to
+     */
     private static void setupClientAppender(LanguageClient client) {
         LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
         LanguageClientAppender appender = new LanguageClientAppender(client);

ls/service/src/main/resources/application.properties

@@ -1,3 +1,4 @@
 spring.main.banner-mode=off
 spring.main.log-startup-info=false
-spring.profiles.active=default
+spring.profiles.active=default
+spring.main.web-application-type=none