Use XVFB on Linux CI, allows running the client prod tasks on a headless OS (#1243)

build.gradle

@@ -270,6 +270,11 @@ test {
 			maxRetries = 3
 		}
 	}
+
+	testLogging {
+		// Log everything to the console
+		setEvents(TestLogEvent.values().toList())
+	}
 }
 
 // Workaround https://github.com/gradle/gradle/issues/25898
@@ -283,7 +288,7 @@ tasks.withType(Test).configureEach {
 }
 
 
-import org.gradle.api.internal.artifacts.configurations.ConfigurationRoles
+import org.gradle.api.tasks.testing.logging.TestLogEvent
 import org.gradle.util.GradleVersion
 import org.w3c.dom.Document
 import org.w3c.dom.Element

src/main/java/net/fabricmc/loom/task/prod/ClientProductionRunTask.java

@@ -43,6 +43,16 @@ import net.fabricmc.loom.util.Platform;
  */
 @ApiStatus.Experimental
 public abstract non-sealed class ClientProductionRunTask extends AbstractProductionRunTask {
+	/**
+	 * Whether to use XVFB to run the game, using a virtual framebuffer. This is useful for CI environments that don't have a display server.
+	 *
+	 * <p>Defaults to true only on Linux and when the "CI" environment variable is set.
+	 *
+	 * <p>XVFB must be installed, on Debian-based systems you can install it with: <code>apt install -y xvfb</code>
+	 */
+	@Input
+	public abstract Property<Boolean> getUseXVFB();
+
 	// Internal options
 	@Input
 	protected abstract Property<String> getAssetsIndex();
@@ -52,6 +62,11 @@ public abstract non-sealed class ClientProductionRunTask extends AbstractProduct
 
 	@Inject
 	public ClientProductionRunTask() {
+		getUseXVFB().convention(getProject().getProviders().environmentVariable("CI")
+				.map(value -> Platform.CURRENT.getOperatingSystem().isLinux())
+				.orElse(false)
+		);
+
 		getAssetsIndex().set(getExtension().getMinecraftVersion()
 				.map(minecraftVersion -> getExtension()
 						.getMinecraftProvider()
@@ -71,6 +86,22 @@ public abstract non-sealed class ClientProductionRunTask extends AbstractProduct
 		dependsOn("downloadAssets");
 	}
 
+	@Override
+	protected void configureCommand(ExecSpec exec) {
+		if (getUseXVFB().get()) {
+			if (!Platform.CURRENT.getOperatingSystem().isLinux()) {
+				throw new UnsupportedOperationException("XVFB is only supported on Linux");
+			}
+
+			exec.commandLine("/usr/bin/xvfb-run");
+			exec.args("-a", getJavaLauncher().get().getExecutablePath());
+
+			return;
+		}
+
+		super.configureCommand(exec);
+	}
+
 	@Override
 	protected void configureJvmArgs(ExecSpec exec) {
 		super.configureJvmArgs(exec);

src/test/groovy/net/fabricmc/loom/test/integration/RunConfigTest.groovy

@@ -24,8 +24,11 @@
 
 package net.fabricmc.loom.test.integration
 
+import java.util.concurrent.TimeUnit
+
 import spock.lang.IgnoreIf
 import spock.lang.Specification
+import spock.lang.Timeout
 import spock.lang.Unroll
 import spock.util.environment.RestoreSystemProperties
 
@@ -157,19 +160,30 @@ class RunConfigTest extends Specification implements GradleProjectTestTrait {
 		version << STANDARD_TEST_VERSIONS
 	}
 
+	@Timeout(value = 10, unit = TimeUnit.MINUTES)
 	@Unroll
-	@IgnoreIf({ System.getenv("CI") != null }) // This test is disabled on CI because it launches a real client and cannot run headless.
+	@IgnoreIf({ !os.linux }) // XVFB is installed on the CI for this test
 	def "prod client (gradle #version)"() {
 		setup:
 		def gradle = gradleProject(project: "minimalBase", version: version)
 		gradle.buildGradle << '''
+				configurations {
+					productionMods
+				}
+
                 dependencies {
                     minecraft "com.mojang:minecraft:1.21.4"
                     mappings "net.fabricmc:yarn:1.21.4+build.4:v2"
                     modImplementation "net.fabricmc:fabric-loader:0.16.9"
+                    modImplementation "net.fabricmc.fabric-api:fabric-api:0.114.0+1.21.4"
+
+                    productionMods "net.fabricmc.fabric-api:fabric-api:0.114.0+1.21.4"
                 }
 
-                tasks.register("prodClient", net.fabricmc.loom.task.prod.ClientProductionRunTask)
+                tasks.register("prodClient", net.fabricmc.loom.task.prod.ClientProductionRunTask) {
+                	mods.from(configurations.productionMods)
+                	jvmArgs.add("-Dfabric.client.gametest")
+                }
             '''
 		when:
 		def result = gradle.run(task: "prodClient")