Default mappings to official, closes #1041

Author: LexManos

src/main/java/net/minecraftforge/gradle/MinecraftMappings.java

@@ -4,6 +4,8 @@
  */
 package net.minecraftforge.gradle;
 
+import org.jspecify.annotations.Nullable;
+
 import java.io.Serializable;
 
 /// The mappings used for the Minecraft dependency.
@@ -18,5 +20,5 @@ public interface MinecraftMappings extends Serializable {
     /// Gets the version for these mappings (i.e. `1.21.11`)
     ///
     /// @return The version
-    String getVersion();
+    @Nullable String getVersion();
 }

src/main/java/net/minecraftforge/gradle/internal/MinecraftExtensionImpl.java

@@ -93,6 +93,7 @@ static void register(
     public MinecraftExtensionImpl(ForgeGradlePlugin plugin) {
         this.plugin = plugin;
         this.mavenizerOutput.convention(plugin.rootProjectDirectory().dir(".gradle/mavenizer/repo").map(this.problems.ensureFileLocation()));
+        this.mappings.convention(getObjects().newInstance(MinecraftMappingsImpl.class, "official", ""));
     }
 
     @Override
@@ -432,9 +433,9 @@ public MavenizerInstance dependency(
 
                         var mappings = minecraftDependency.getMappings();
                         if ("parchment".equals(mappings.getChannel()))
-                            ret.addAll(List.of("--parchment", mappings.getVersion()));
+                            ret.addAll(List.of("--parchment", Objects.requireNonNull(mappings.getVersion())));
                         else if (!"official".equals(mappings.getChannel()))
-                            ret.addAll(List.of("--mappings", mappings.getChannel() + ':' + mappings.getVersion()));
+                            ret.addAll(List.of("--mappings", mappings.getChannel() + ':' + Objects.requireNonNull(mappings.getVersion())));
 
                         for (var repo : this.getRepositories()) {
                             if (MAVENIZER_REPO_NAME.equals(repo.getName()))

src/main/java/net/minecraftforge/gradle/internal/MinecraftMappingsImpl.java

@@ -5,6 +5,7 @@
 package net.minecraftforge.gradle.internal;
 
 import org.gradle.api.model.ObjectFactory;
+import org.jspecify.annotations.Nullable;
 
 import javax.inject.Inject;
 import java.io.Serial;
@@ -13,7 +14,7 @@ abstract class MinecraftMappingsImpl implements MinecraftMappingsInternal {
     private static final @Serial long serialVersionUID = 6944934115402768018L;
 
     private final String channel;
-    private final String version;
+    private final @Nullable String version;
 
     protected abstract @Inject ObjectFactory getObjects();
 
@@ -23,6 +24,8 @@ public MinecraftMappingsImpl(String channel, String version) {
         this.channel = Util.checkMappingsParam(problems, channel, "channel");
         if (this.channel.equals("parchment"))
             this.version = ParchmentVersion.parse(Util.checkMappingsParam(problems, version, "version")).toFriendly();
+        else if (this.channel.equals("official"))
+            this.version = version.isEmpty() ? null : version;
         else
             this.version = Util.checkMappingsParam(problems, version, "version");
     }
@@ -33,7 +36,7 @@ public String getChannel() {
     }
 
     @Override
-    public String getVersion() {
+    public @Nullable String getVersion() {
         return this.version;
     }
 }

src/main/java/net/minecraftforge/gradle/internal/Util.java

@@ -22,7 +22,7 @@
 
 final class Util extends SharedUtil {
     static String checkMappingsParam(ForgeGradleProblems problems, @Nullable Object param, String name) {
-        if (param == null)
+        if (param == null || param.toString().isEmpty())
             throw problems.nullMappingsParam(name);
 
         return param.toString();