Add some basic detection when we have a mismatch between the mappings…

… version and the game version.

This just makes the error more understandable as to what's gone wrong.

gradle.properties

@@ -5,7 +5,7 @@ group = org.quiltmc
 description = The mod loading component of Quilt
 url = https://github.com/quiltmc/quilt-loader
 # Don't forget to change this in QuiltLoaderImpl as well
-quilt_loader = 0.21.2-beta.1
+quilt_loader = 0.21.2-beta.2
 
 # Fabric & Quilt Libraries
 asm = 9.5

minecraft/src/main/java/org/quiltmc/loader/impl/game/minecraft/MinecraftGameProvider.java

@@ -16,6 +16,7 @@
 
 package org.quiltmc.loader.impl.game.minecraft;
 
+import java.io.File;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -32,6 +33,8 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.quiltmc.loader.api.ModDependency;
 import org.quiltmc.loader.api.ModDependencyIdentifier;
@@ -378,10 +381,31 @@ public void initialize(QuiltLauncher launcher) {
 				launcher.hideParentPath(obf);
 			}
 
-			obfJars = GameProviderHelper.deobfuscate(obfJars,
-					getGameId(), getNormalizedGameVersion(),
-					getLaunchDirectory(),
-					launcher);
+			try {
+				obfJars = GameProviderHelper.deobfuscate(obfJars,
+						getGameId(), getNormalizedGameVersion(),
+						getLaunchDirectory(),
+						launcher);
+			} catch (RuntimeException e) {
+				if ("Unfixable conflicts".equals(e.getMessage())) {
+					String source = launcher.getMappingConfiguration().getMappingsSource().replace(File.separator, "/");
+					// Check for known cases
+					// Intermediary
+					Pattern intermediary = Pattern.compile(".+/net/fabricmc/intermediary/([^/]+)/intermediary-([^/]+)\\.jar.+");
+					Matcher matcher = intermediary.matcher(source);
+					if (matcher.matches()) {
+						String version1 = matcher.group(1);
+						String version2 = matcher.group(2);
+						if (version1.equals(version2)) {
+							// Okay, probably an intermediary version
+							if (!version1.equals(getRawGameVersion())) {
+								throw new RuntimeException("Mappings version is mismatched with minecraft version " + version1 + " vs mc " + getRawGameVersion(), e);
+							}
+						}
+					}
+				}
+				throw e;
+			}
 
 			for (int i = 0; i < gameJars.size(); i++) {
 				Path newJar = obfJars.get(names[i]);

src/main/java/org/quiltmc/loader/impl/QuiltLoaderImpl.java

@@ -129,7 +129,7 @@ public final class QuiltLoaderImpl {
 
 	public static final int ASM_VERSION = Opcodes.ASM9;
 
-	public static final String VERSION = "0.21.2-beta.1";
+	public static final String VERSION = "0.21.2-beta.2";
 	public static final String MOD_ID = "quilt_loader";
 	public static final String DEFAULT_MODS_DIR = "mods";
 	public static final String DEFAULT_CACHE_DIR = ".cache";

src/main/java/org/quiltmc/loader/impl/launch/common/MappingConfiguration.java

@@ -43,6 +43,7 @@ public final class MappingConfiguration {
 
 	private String gameId;
 	private String gameVersion;
+	private String mappingsSource;
 	private TinyTree mappings;
 
 	public String getGameId() {
@@ -57,6 +58,12 @@ public String getGameVersion() {
 		return gameVersion;
 	}
 
+	public String getMappingsSource() {
+		initialize();
+
+		return mappingsSource;
+	}
+
 	public boolean matches(String gameId, String gameVersion) {
 		initialize();
 
@@ -112,6 +119,7 @@ private void initialize() {
 
 					if (mappings.getMetadata().getNamespaces().contains(getTargetNamespace())) {
 						this.mappings = mappings;
+						this.mappingsSource = url.toString();
 						break;
 					}