Build with loom-back-compat and a Java toolchain per version

Prepares the build for 26.x, which ships unobfuscated and needs Java 25
(#39):

- loom-back-compat applies the remapping Loom to 1.21.x and would apply
  the plain one to 26.x. loom_version becomes loomx.loom_version.
- Each version compiles with its Java toolchain (21 for 1.21.x, 25 for
  26.x), and the mixin configs take their compatibility level from it.
  The foojay resolver downloads a missing JDK; CI installs 21 and 25.
- buildAll collects remapJar's output, or jar's where there's nothing
  to remap.
- fabric.mod.json depends on fabric-api, Fabric API's mod id; 26.x's
  jar no longer provides the old "fabric" alias.

Nothing changes for the 1.21.x jars.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.gitea/workflows/check.yml

@@ -19,15 +19,20 @@ jobs:
       # The JDK comes from the runner's tool cache. `cache: gradle` stores Gradle's
       # dependencies, Loom's Minecraft cache and the build cache in the runner's
       # actions cache.
-      - name: Set up Java 21
+      # 1.21.x builds with Java 21 and 26.x with Java 25. The last version listed is the default
+      # (Gradle runs on it), and the Gradle commands below point toolchain detection at both.
+      - name: Set up Java 25 and 21
         uses: actions/setup-java@v5
         with:
           distribution: temurin
-          java-version: 21
+          java-version: |
+            25
+            21
           cache: gradle
 
       - name: Compile all versions
         run: |
           chmod +x gradlew
           # --continue reports every version that fails, not just the first.
-          ./gradlew compileJava --no-daemon --stacktrace --continue
+          ./gradlew compileJava --no-daemon --stacktrace --continue \
+            -Porg.gradle.java.installations.fromEnv=JAVA_HOME_21_X64,JAVA_HOME_25_X64

.gitea/workflows/release.yml

@@ -47,11 +47,15 @@ jobs:
       # The JDK comes from the runner's tool cache. `cache: gradle` stores Gradle's
       # dependencies, Loom's Minecraft cache and the build cache in the runner's
       # actions cache.
-      - name: Set up Java 21
+      # 1.21.x builds with Java 21 and 26.x with Java 25. The last version listed is the default
+      # (Gradle runs on it), and the Gradle commands below point toolchain detection at both.
+      - name: Set up Java 25 and 21
         uses: actions/setup-java@v5
         with:
           distribution: temurin
-          java-version: 21
+          java-version: |
+            25
+            21
           cache: gradle
 
       - name: Build all versions
@@ -59,7 +63,8 @@ jobs:
           chmod +x gradlew
           # buildAll remaps every Minecraft version (two at a time, to stay within the
           # Gradle heap) into build/allJars.
-          ./gradlew buildAll --no-daemon --stacktrace
+          ./gradlew buildAll --no-daemon --stacktrace \
+            -Porg.gradle.java.installations.fromEnv=JAVA_HOME_21_X64,JAVA_HOME_25_X64
 
       - name: Upload jars to the release
         env:

build.gradle.kts

@@ -1,11 +1,14 @@
 // Builds one Minecraft version from the shared src/. Stonecutter runs this for each version in
 // stonecutterVersions (settings.gradle.kts), with that version's versions/<v>/gradle.properties.
 plugins {
-    id("net.fabricmc.fabric-loom-remap")
+    id("dev.kikugie.loom-back-compat")
     `maven-publish`
 }
 
 val minecraftVersion = property("minecraft_version") as String
+// The Minecraft versions the jar loads on (fabric.mod.json); a range where hotfixes share a jar.
+val minecraftCompat = findProperty("minecraft_compat") as String? ?: minecraftVersion
+val javaVersion = if (sc.current.parsed >= "26.1") 25 else 21
 val loaderVersion = property("loader_version") as String
 
 version = "${property("mod_version")}+$minecraftVersion"
@@ -17,7 +20,7 @@ base {
 
 dependencies {
     minecraft("com.mojang:minecraft:$minecraftVersion")
-    mappings(loom.officialMojangMappings())
+    loomx.applyMojangMappings()
     modImplementation("net.fabricmc:fabric-loader:$loaderVersion")
     modImplementation("net.fabricmc.fabric-api:fabric-api:${property("fabric_api_version")}")
 
@@ -42,23 +45,23 @@ dependencies {
 tasks.processResources {
     val values = mapOf(
         "version" to project.version.toString(),
-        "minecraft_version" to minecraftVersion,
+        "minecraft_version" to minecraftCompat,
         "loader_version" to loaderVersion,
+        "java" to "JAVA_$javaVersion",
     )
     inputs.properties(values)
     filteringCharset = "UTF-8"
-    filesMatching("fabric.mod.json") { expand(values) }
+    filesMatching(listOf("fabric.mod.json", "*.mixins.json")) { expand(values) }
 }
 
 tasks.withType<JavaCompile>().configureEach {
-    options.release = 21
+    options.release = javaVersion
 }
 
 java {
     // Loom attaches the sources jar to remapSourcesJar and build.
     withSourcesJar()
-    sourceCompatibility = JavaVersion.VERSION_21
+    toolchain.languageVersion = JavaLanguageVersion.of(javaVersion)
-    targetCompatibility = JavaVersion.VERSION_21
 }
 
 tasks.jar {

gradle.properties

@@ -11,5 +11,5 @@ mod_version=0.1.4-beta
 # Saturn's emote library (git.selimaj.dev/saturnclientmc/emotes)
 emotes_version=0.1.2
 
-# Loom, for every Minecraft version (read in settings.gradle.kts).
+# Loom, for every Minecraft version (read by loom-back-compat).
-loom_version=1.17.21
+loomx.loom_version=1.17.21

settings.gradle.kts

@@ -5,16 +5,15 @@ pluginManagement {
         gradlePluginPortal()
         mavenCentral()
     }
-
-    // Loom's version for build.gradle.kts, which can't read properties in its plugins block.
-    val loom_version: String by settings
-    plugins {
-        id("net.fabricmc.fabric-loom-remap") version loom_version
-    }
 }
 
 plugins {
+    // Downloads the Java toolchain a version needs (Java 25 for 26.1+) when it isn't installed.
+    id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
     id("dev.kikugie.stonecutter") version "0.9.8"
+    // Picks the Loom variant per version: remapping for 1.21.x, plain for the unobfuscated 26.1+.
+    // Its version is loomx.loom_version in gradle.properties.
+    id("dev.kikugie.loom-back-compat") version "0.4.2"
 }
 
 rootProject.name = "saturn-client"
@@ -23,7 +22,9 @@ include("common")
 
 // Versions built by Stonecutter from the shared src/ (see stonecutter.gradle.kts). Each one's
 // versions/<v>/gradle.properties holds its Minecraft, Fabric Loader and Fabric API versions.
-val stonecutterVersions = listOf("1.21.4", "1.21.5", "1.21.6", "1.21.7", "1.21.8", "1.21.9", "1.21.10", "1.21.11")
+val stonecutterVersions = listOf(
+    "1.21.4", "1.21.5", "1.21.6", "1.21.7", "1.21.8", "1.21.9", "1.21.10", "1.21.11",
+)
 
 stonecutter {
     create(rootProject) {

src/main/resources/fabric.mod.json

@@ -22,7 +22,7 @@
   ],
   "depends": {
     "fabricloader": ">=${loader_version}",
-    "fabric": "*",
+    "fabric-api": "*",
     "minecraft": "${minecraft_version}"
   }
 }

src/main/resources/features.mixins.json

@@ -2,7 +2,7 @@
   "required": true,
   "minVersion": "0.8",
   "package": "org.saturnclient.impl.features.mixins",
-  "compatibilityLevel": "JAVA_21",
+  "compatibilityLevel": "${java}",
   "client": [
     "render.GameRendererMixin",
     "render.LightmapTextureManagerMixin",

src/main/resources/impl.mixins.json

@@ -2,7 +2,7 @@
   "required": true,
   "minVersion": "0.8",
   "package": "org.saturnclient.impl.mixins",
-  "compatibilityLevel": "JAVA_21",
+  "compatibilityLevel": "${java}",
   "client": [
     "IdentifierMixin",
     "ItemStackMixin",

src/main/resources/saturnclient.mixins.json

@@ -2,14 +2,15 @@
   "required": true,
   "minVersion": "0.8",
   "package": "org.saturnclient.saturnclient.mixin",
-  "compatibilityLevel": "JAVA_21",
+  "compatibilityLevel": "${java}",
   "client": [
     "TabListMixin",
     "PlayerEntityRendererMixin",
     "WhoAmI",
     "DrawContextAccessor",
     "SplashOverlayMixin",
-    "SetScreenMixin"
+    "SetScreenMixin",
+    "GuiRendererMixin"
   ],
   "injectors": {
     "defaultRequire": 1

stonecutter.gradle.kts

@@ -69,17 +69,22 @@ subprojects {
 
 tasks.register("buildAll") {
     group = "build"
-    description = "Builds every Minecraft version's remapped jar and collects them in build/allJars"
+    description = "Builds every Minecraft version's mod jar and collects them in build/allJars"
 
-    val remapJars = subprojects.flatMap { it.tasks.matching { task -> task.name == "remapJar" } }
+    // The mod jar is remapJar's output for 1.21.x, and jar's for 26.1+, which isn't obfuscated.
-    dependsOn(remapJars)
+    val modJars = subprojects.filter { it.name != "common" }.flatMap { project ->
+        val unobfuscated = project.name.substringBefore('.').toInt() >= 26
+        val task = if (unobfuscated) "jar" else "remapJar"
+        project.tasks.matching { it.name == task }
+    }
+    dependsOn(modJars)
 
     doLast {
         val outputDir = layout.buildDirectory.dir("allJars").get().asFile
         outputDir.mkdirs()
-        remapJars.map { (it as AbstractArchiveTask).archiveFile.get().asFile }
+        modJars.map { (it as AbstractArchiveTask).archiveFile.get().asFile }
             .filter { it.exists() && !it.name.contains("sources") }
             .forEach { it.copyTo(outputDir.resolve(it.name), overwrite = true) }
-        println("All remapped jars collected in: $outputDir")
+        println("All mod jars collected in: $outputDir")
     }
 }