display error screen when java version is > 21

Author: brachy84

src/main/java/com/cleanroommc/groovyscript/GroovyScript.java

@@ -55,6 +55,7 @@
 import net.minecraftforge.fml.common.gameevent.InputEvent;
 import net.minecraftforge.fml.relauncher.FMLInjectionData;
 import net.minecraftforge.fml.relauncher.FMLLaunchHandler;
+import net.minecraftforge.fml.relauncher.Side;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.jetbrains.annotations.ApiStatus;
@@ -101,6 +102,8 @@ public class GroovyScript {
 
     @Mod.EventHandler
     public void onConstruction(FMLConstructionEvent event) {
+        int jv = getJavaVersion();
+        if (jv > 21) handleJavaVersionException(jv, event.getSide());
         if (!SandboxData.isInitialised()) {
             LOGGER.throwing(new IllegalStateException("Sandbox data should have been initialised by now, but isn't! Trying to initialize again."));
             SandboxData.initialize((File) FMLInjectionData.data()[6], LOGGER);
@@ -127,6 +130,17 @@ public void onConstruction(FMLConstructionEvent event) {
         getRunConfig().initPackmode();
     }
 
+    private static void handleJavaVersionException(int version, Side side) {
+        String msg1 = "Groovy does not work with Java versions greater than 21 currently.";
+        String msg2 = "Please downgrade to Java 21 or lower. Your current Java version is " + version + ".";
+        if (side.isClient()) {
+            // the super class of this exception is client only (since the screen only works on client)
+            throw new IncompatibleJavaException(msg1 + "\n" + msg2);
+        } else {
+            throw new IllegalStateException(msg1 + " " + msg2);
+        }
+    }
+
     @Mod.EventHandler
     public void onInit(FMLInitializationEvent event) {
         if (ModSupport.TINKERS_CONSTRUCT.isLoaded()) TinkersConstruct.init();
@@ -312,4 +326,16 @@ public static void doForGroovyScript(Runnable runnable) {
         runnable.run();
         Loader.instance().setActiveModContainer(current);
     }
+
+    public static int getJavaVersion() {
+        // from stack overflow
+        String version = System.getProperty("java.version");
+        if (version.startsWith("1.")) {
+            version = version.substring(2, 3);
+        } else {
+            int dot = version.indexOf(".");
+            if (dot != -1) version = version.substring(0, dot);
+        }
+        return Integer.parseInt(version);
+    }
 }

src/main/java/com/cleanroommc/groovyscript/IncompatibleJavaException.java

@@ -0,0 +1,32 @@
+package com.cleanroommc.groovyscript;
+
+import net.minecraft.client.gui.FontRenderer;
+import net.minecraft.client.gui.GuiErrorScreen;
+import net.minecraftforge.fml.client.CustomModLoadingErrorDisplayException;
+
+import java.util.List;
+
+public class IncompatibleJavaException extends CustomModLoadingErrorDisplayException {
+
+    private final String msg;
+
+    public IncompatibleJavaException(String msg) {
+        this.msg = msg;
+    }
+
+    @Override
+    public void initGui(GuiErrorScreen errorScreen, FontRenderer fontRenderer) {}
+
+    @Override
+    public void drawScreen(GuiErrorScreen errorScreen, FontRenderer fontRenderer, int mouseRelX, int mouseRelY, float tickTime) {
+        List<String> lines = fontRenderer.listFormattedStringToWidth(this.msg, errorScreen.width - 40);
+        int buttonSpace = 20 + 2 * 18; // button is 18 pixel high + 18 pixel margin on both sides
+        int y = (errorScreen.height - buttonSpace) / 2 - (fontRenderer.FONT_HEIGHT * 2 + 1) / 2; // font height * 2 /
+        for (String line : lines) {
+            int width = fontRenderer.getStringWidth(line);
+            int x = errorScreen.width / 2 - width / 2;
+            fontRenderer.drawStringWithShadow(line, x, y, 0xFFFFFFFF);
+            y += fontRenderer.FONT_HEIGHT;
+        }
+    }
+}

src/main/java/com/cleanroommc/groovyscript/core/mixin/LoaderControllerMixin.java

@@ -2,13 +2,17 @@
 
 import com.cleanroommc.groovyscript.GroovyScript;
 import com.cleanroommc.groovyscript.sandbox.LoadStage;
+import net.minecraftforge.fml.client.CustomModLoadingErrorDisplayException;
 import net.minecraftforge.fml.common.LoadController;
 import net.minecraftforge.fml.common.LoaderState;
+import net.minecraftforge.fml.common.ModContainer;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
+import java.lang.reflect.InvocationTargetException;
+
 @Mixin(value = LoadController.class, remap = false)
 public class LoaderControllerMixin {
 
@@ -24,4 +28,15 @@ public void preInit(LoaderState state, Object[] eventData, CallbackInfo ci) {
             GroovyScript.runGroovyScriptsInLoader(LoadStage.POST_INIT);
         }
     }
+
+    @Inject(method = "errorOccurred", at = @At(value = "NEW", target = "(Ljava/lang/String;Ljava/lang/Object;Ljava/lang/Object;)Lorg/apache/logging/log4j/message/FormattedMessage;", shift = At.Shift.BEFORE))
+    public void errorOccured(ModContainer modContainer, Throwable exception, CallbackInfo ci) throws Throwable {
+        if (exception instanceof InvocationTargetException) {
+            exception = exception.getCause();
+        }
+        if (exception instanceof CustomModLoadingErrorDisplayException) {
+            // normally every exception gets wrapped in a LoaderException making these """custom""" exceptions useless, thanks cpw
+            throw exception;
+        }
+    }
 }