The new javaAgent configuration is no longer non-transitive

This works around a GCV bug which fails to apply constraints to
non-transitive configurations.
See palantir/gradle-consistent-versions#677

gradle-sls-packaging/src/main/java/com/palantir/gradle/dist/service/JavaServiceDistributionPlugin.java

@@ -92,16 +92,7 @@ public void apply(Project project) {
         });
 
         Configuration runtimeClasspath = project.getConfigurations().getByName("runtimeClasspath");
-        Configuration javaAgentConfiguration = project.getConfigurations()
-                .create("javaAgent", new Action<Configuration>() {
-                    @Override
-                    public void execute(Configuration javaAgent) {
-                        // Each javaAgent is applied via a '-javaagent:path/to/agent.jar' argument
-                        // Agents should have no dependencies, but this allows us to avoid adding
-                        // non-agent jars as agents if any are listed.
-                        javaAgent.setTransitive(false);
-                    }
-                });
+        Configuration javaAgentConfiguration = project.getConfigurations().create("javaAgent");
 
         // Set default configuration to look for product dependencies to be runtimeClasspath
         distributionExtension.setProductDependenciesConfig(runtimeClasspath);

gradle-sls-packaging/src/main/java/com/palantir/gradle/dist/service/tasks/LaunchConfigTask.java

@@ -27,6 +27,8 @@
 import java.nio.file.Files;
 import java.util.List;
 import java.util.Map;
+import java.util.jar.Attributes;
+import java.util.jar.JarFile;
 import java.util.stream.Collectors;
 import org.gradle.api.DefaultTask;
 import org.gradle.api.JavaVersion;
@@ -204,10 +206,25 @@ private static void writeConfig(LaunchConfig config, File scriptFile) throws IOE
 
     private List<String> javaAgentArgs() {
         return getJavaAgents().getFiles().stream()
-                .map(file -> "-javaagent:service/lib/agent/" + file.getName())
+                .map(file -> "-javaagent:service/lib/agent/"
+                        + validateJavaAgent(file).getName())
                 .collect(Collectors.toList());
     }
 
+    /** Returns the input file. An exception is thrown if the {@code agentFile} is not a java agent. */
+    private static File validateJavaAgent(File agentFile) {
+        try {
+            JarFile agentJarFile = new JarFile(agentFile);
+            if (!agentJarFile.getManifest().getMainAttributes().containsKey(new Attributes.Name("Premain-Class"))) {
+                throw new IllegalArgumentException("Jar file " + agentFile.getName()
+                        + " is not a java agent and contains no Premain-Class manifest entry");
+            }
+            return agentFile;
+        } catch (IOException e) {
+            throw new IllegalArgumentException(e.getMessage(), e);
+        }
+    }
+
     private static List<String> relativizeToServiceLibDirectory(FileCollection files) {
         return files.getFiles().stream()
                 .map(file -> "service/lib/" + file.getName())

gradle-sls-packaging/src/test/groovy/com/palantir/gradle/dist/service/JavaServiceDistributionPluginTests.groovy

@@ -1102,6 +1102,26 @@ class JavaServiceDistributionPluginTests extends GradleIntegrationSpec {
         fileExists('dist/service-name-0.0.1/service/lib/agent/byte-buddy-agent-1.10.21.jar')
     }
 
+    def 'fails at build time when non-agent jars are provided as agents'() {
+        createUntarBuildFile(buildFile)
+        buildFile << """
+            dependencies {
+                compile files("${EXTERNAL_JAR}")
+                javaAgent files("${EXTERNAL_JAR}")
+            }
+            tasks.jar.archiveBaseName = "internal"
+            distribution {
+                javaVersion 11
+            }""".stripIndent()
+        file('src/main/java/test/Test.java') << "package test;\npublic class Test {}"
+
+        when:
+        def result = runTasksAndFail(':distTar')
+
+        then:
+        result.output.contains('is not a java agent and contains no Premain-Class manifest entry')
+    }
+
     private static createUntarBuildFile(File buildFile) {
         buildFile << '''
             plugins {