Fixed the gui system closing the whole game if the forked gui process…

… encountered an error, rather than returning the error to the original process.

src/main/java/org/quiltmc/loader/impl/gui/AbstractWindow.java

@@ -24,6 +24,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.function.Supplier;
 
 import org.quiltmc.loader.api.LoaderValue;
 import org.quiltmc.loader.api.LoaderValue.LObject;
@@ -126,15 +127,22 @@ void onClosed() {
 		sendSignal("closed");
 	}
 
-	void waitUntilClosed() throws LoaderGuiException {
+	void waitUntilClosed(Supplier<Error> errorChecker) throws LoaderGuiException {
 		try {
 			while (true) {
 				try {
 					onClosedFuture.get(1, TimeUnit.SECONDS);
 					break;
 				} catch (TimeoutException e) {
 					if (QuiltForkComms.getCurrentComms() == null) {
-						throw new LoaderGuiException("Forked communication failure; check the log for details!", e);
+						Error error = errorChecker.get();
+						if (error == null) {
+							throw new LoaderGuiException("Forked communication failure; check the log for details!", e);
+						} else {
+							LoaderGuiException ex = new LoaderGuiException("Forked communication failure!", error);
+							ex.addSuppressed(e);
+							throw ex;
+						}
 					}
 				}
 			}

src/main/java/org/quiltmc/loader/impl/gui/QuiltFork.java

@@ -56,6 +56,7 @@ public class QuiltFork {
 	private static final QuiltForkComms COMMS;
 	private static final LoaderValueHelper<IOException> HELPER = LoaderValueHelper.IO_EXCEPTION;
 	private static final IOException FORK_EXCEPTION;
+	private static Error previousServerError;
 
 	static {
 		GameProvider provider = QuiltLoaderImpl.INSTANCE.getGameProvider();
@@ -130,13 +131,18 @@ public static void open(QuiltLoaderWindow<?> window, boolean shouldWait) throws
 			return;
 		}
 
+		if (previousServerError != null) {
+			// Gui NOT disabled, but it previously crashed.
+			throw new LoaderGuiException("The gui server encountered an error!", previousServerError);
+		}
+
 		AbstractWindow<?> realWindow = (AbstractWindow<?>) window;
 
 		realWindow.send();
 		realWindow.open();
 
 		if (shouldWait) {
-			realWindow.waitUntilClosed();
+			realWindow.waitUntilClosed(() -> previousServerError);
 		}
 	}
 
@@ -187,10 +193,15 @@ private static void handleMessageFromServer0(LoaderValue msg) throws IOException
 			switch (type) {
 				case ForkCommNames.ID_EXCEPTION: {
 					// The server encountered an exception
-					// We should really store the exception, but for now just exit
+					LoaderValue detail = packet.get("detail");
+					if (detail == null || detail.type() != LType.STRING) {
+						Log.error(LogCategory.COMMS, "The gui-server encountered an unknown error!");
+						previousServerError = new Error("[Unknown error: the gui server didn't send a detail trace]");
+					} else {
+						Log.error(LogCategory.COMMS, "The gui-server encountered an error:\n" + detail.asString());
+						previousServerError = new Error("Previous error stacktrace:\n" + detail.asString());
+					}
 					COMMS.close();
-					Log.error(LogCategory.COMMS, "The gui-server encountered an error!");
-					System.exit(1);
 					return;
 				}
 				case ForkCommNames.ID_GUI_OBJECT_UPDATE: {

src/main/java/org/quiltmc/loader/impl/gui/QuiltForkComms.java

@@ -23,6 +23,9 @@
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.io.StringWriter;
 import java.lang.ProcessBuilder.Redirect;
 import java.net.InetAddress;
 import java.net.Socket;
@@ -380,6 +383,14 @@ private void readMessage(LoaderValue value) {
 			} catch (Throwable t) {
 				Map<String, LoaderValue> map = new HashMap<>();
 				map.put("__TYPE", lvf().string(ForkCommNames.ID_EXCEPTION));
+
+				StringWriter sw = new StringWriter();
+				try (PrintWriter printer = new PrintWriter(sw)) {
+					t.printStackTrace(printer);
+					printer.flush();
+				}
+				map.put("detail", lvf().string(sw.toString()));
+
 				send(lvf().object(map));
 				throw t;
 			}

src/main/resources/changelog/0.26.1.txt

@@ -1,3 +1,4 @@
 Bug Fixes:
 
 - Fixed crash reports being printed to system out, rather than the log. (This is a problem for launchers which don't replay sysout, like Modrinth)
+- Fixed the gui system closing the whole game if the forked gui process encountered an error, rather than returning the error to the original process.