feat(*): Require a minimum of Java 11 at runtime

build.gradle

@@ -50,7 +50,11 @@ subprojects {
       ci true
     }
     mitLicense()
-    javaVersions().testWith(11, 17, 20)
+    javaVersions {
+      target 11
+      minimumToolchain 17
+      testWith(11, 17, 20)
+    }
 
     signWithKeyFromPrefixedProperties("kyori")
     configurePublications {

gradle/libs.versions.toml

@@ -8,7 +8,7 @@ gradlePluginPublish = "1.2.1"
 immutables = "2.9.3"
 indra = "3.1.2"
 jetbrainsAnnotations = "24.0.1"
-jgit = "5.13.0.+" # stay on 5.x series, 6+ requires Java 11
+jgit = "6.6.0.+" # stay on 5.x series, 6+ requires Java 11
 junit = "5.10.0"
 kotlin = "1.9.10"
 mammoth = "1.3.1"
@@ -48,8 +48,7 @@ gradlePluginPublish = { module = "com.gradle.publish:plugin-publish-plugin", ver
 nexusPublishPlugin = { module = "io.github.gradle-nexus:publish-plugin", version = "1.3.0" }
 
 # spotless-licenser
-spotlessLegacy = { module = "com.diffplug.spotless:spotless-plugin-gradle", version = "6.13.0" } # build against this, for J8 support
-spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version.ref = "spotless" } # published as a dep on a special J11+ variant
+spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version.ref = "spotless" }
 
 # testlib
 mammoth-test = { module = "net.kyori:mammoth-test", version.ref = "mammoth" }

indra-common/src/main/java/net/kyori/indra/internal/IndraExtensionImpl.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of indra, licensed under the MIT License.
  *
- * Copyright (c) 2020-2022 KyoriPowered
+ * Copyright (c) 2020-2023 KyoriPowered
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -62,7 +62,7 @@
 public class IndraExtensionImpl implements IndraExtension {
 
   private static final Logger LOGGER = Logging.getLogger(IndraExtensionImpl.class);
-  private static final String DEFAULT_CHECKSTYLE_VERSION = "9.3";
+  private static final String DEFAULT_CHECKSTYLE_VERSION = "10.12.3";
 
   private final Property<ContinuousIntegration> ci;
   private final Property<Issues> issues;

indra-licenser-spotless/build.gradle

@@ -1,72 +1,12 @@
-import org.gradle.api.attributes.java.TargetJvmVersion
-import org.gradle.api.plugins.internal.JavaConfigurationVariantMapping
-
-static def transferAttributes(HasAttributes src, HasAttributes dest) {
-  def destAttrs = dest.attributes
-  src.attributes.keySet().each {
-    destAttrs.attribute(it, src.attributes.getAttribute(it))
-  }
-}
-
-def duplicateConfiguration(Configuration src, String name, Configuration parent) {
-  configurations.create(name) {
-    canBeConsumed = true
-    canBeResolved = false
-    visible = true
-
-    transferAttributes(src, delegate)
-    attributes.attribute(TargetJvmVersion.TARGET_JVM_VERSION_ATTRIBUTE, 11)
-
-    outgoing.variants.addAll(src.outgoing.variants)
-    outgoing.variants.configureEach {
-      it.attributes.attribute(TargetJvmVersion.TARGET_JVM_VERSION_ATTRIBUTE, 11)
-    }
-    artifacts.addAll(src.artifacts)
-
-    src.incoming.dependencies.each {
-      if (it.group != "com.diffplug.spotless") { // yikes
-        project.dependencies.add(name, it)
-      }
-    }
-    extendsFrom parent
-  }
-}
-
-configurations {
-  java11Deps {
-    canBeConsumed = false
-    canBeResolved = true
-  }
-}
 
 dependencies {
   compileOnlyApi libs.jetbrainsAnnotations
   api libs.mammoth
-  api libs.spotlessLegacy
-  java11Deps libs.spotless
+  api libs.spotless
   testImplementation project(":indra-testlib")
   testImplementation libs.spotless
 }
 
-configurations {
-  // must be after dep declaration because we eagerly read declared deps
-  duplicateConfiguration(apiElements, 'java11ApiElements', java11Deps)
-  duplicateConfiguration(runtimeElements, 'java11RuntimeElements', java11Deps)
-
-  [testCompileClasspath, testRuntimeClasspath].each {
-    it.attributes {
-      attribute(TargetJvmVersion.TARGET_JVM_VERSION_ATTRIBUTE, 11)
-    }
-  }
-}
-
-components.java {
-  // This is technically internal api but because it's our own buildscript we can just update as needed
-  // and it's easier than matching their logic
-  addVariantsFromConfiguration(configurations.java11ApiElements, new JavaConfigurationVariantMapping('compile', true))
-  addVariantsFromConfiguration(configurations.java11RuntimeElements, new JavaConfigurationVariantMapping('runtime', true))
-}
-
 indraPluginPublishing {
   plugin(
     "indra.licenser.spotless",
@@ -76,16 +16,3 @@ indraPluginPublishing {
     ["indra", "licenser", "license-header", "spotless"]
   )
 }
-
-tasks.named('pluginUnderTestMetadata', PluginUnderTestMetadata).configure {
-  pluginClasspath.setFrom(sourceSets.main.output, configurations.java11Deps, configurations.runtimeClasspath)
-}
-
-indra {
-  javaVersions {
-    // TODO(4): remove this since we'll target 11
-    def oldTestWith = testWith().get()
-    testWith().empty()
-    testWith().addAll(oldTestWith.findAll { it != 8})
-  }
-}

settings.gradle

@@ -21,6 +21,16 @@ dependencyResolutionManagement {
 
 rootProject.name = "indra"
 
+def requiredRuntime = 11
+if (JavaVersion.current() < JavaVersion.toVersion(requiredRuntime)) {
+  throw new GradleException("""\
+  You are running a Java version that is too old to build Indra.
+
+  Required: ${requiredRuntime}
+  Current: ${JavaVersion.current()}
+  """.stripIndent())
+}
+
 [
   "indra-common",
   "indra-git",