Gradle: Why the "Could not get unknown property 'com' for root project" error?

Question

Gradle v4.10.2

I built a simple Gradle plugin project by following Writing Gradle Plugins tutorial, and I'm able to build and publish the project into our S3 Maven repo. I DO have the plugin identifier file in my buildSrc/src/main/resources/META-INF/gradle-plugins/com.zift.utilities.properties file with content

implementation-class=com.zift.utilities.ZiftVersionPlugin

Here's my simple code, taken directly from the tutorial

/some_path/zift-version-plugin/buildSrc/src/main/java/com/zift/utilities/ZiftVersionPlugin.java
package com.zift.utilities;

import org.gradle.api.Plugin;
import org.gradle.api.Project;

public class ZiftVersionPlugin implements Plugin<Project> {
    public void apply(Project project) {
        project.getTasks().create("setVersion", ZiftVersion.class, (task) -> {
            task.setProject(project);
        });
        project.getTasks().create("getVersion", ZiftVersion.class, (task) -> {
            task.setProject(project);
        });
    }
}

Now I'm trying to use the plugin via this simple project with this build.gradle file. (I have the variables defined in a gradle.properties file).

buildscript {
  repositories {
    maven {
      url 's3://' + s3_bucket
      credentials(AwsCredentials) {
        accessKey AWS_ACCESS_KEY
        secretKey AWS_SECRET_KEY
      }
    }
  }
  dependencies {
    classpath "com.zift.utilities:zift-version-plugin:0.0.1"
  }
}
apply plugin: com.zift.utilities

When I do a ./gradlew build, the plugin's jar file gets downloaded from our S3 Maven repo and stored locally in Gradle cache, but I get

$ ./gradlew build 

FAILURE: Build failed with an exception.

* Where:
Build file '/Users/me/git-repos/zift/zift-version-plugin-test/build.gradle' line: 16

* What went wrong:
A problem occurred evaluating root project 'zift-version-plugin-test'.
> Could not get unknown property 'com' for root project 'zift-version-plugin-test' of type org.gradle.api.Project.

What am I missing?

Here's the full stack trace if it helps

* Exception is:
org.gradle.api.GradleScriptException: A problem occurred evaluating root project 'zift-version-plugin-test'.
        at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:92)
        at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl$2.run(DefaultScriptPluginFactory.java:206)
        at org.gradle.configuration.ProjectScriptTarget.addConfiguration(ProjectScriptTarget.java:77)
        at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl.apply(DefaultScriptPluginFactory.java:211)
        at org.gradle.configuration.BuildOperationScriptPlugin$1$1.run(BuildOperationScriptPlugin.java:69)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.configuration.BuildOperationScriptPlugin$1.execute(BuildOperationScriptPlugin.java:66)
        at org.gradle.configuration.BuildOperationScriptPlugin$1.execute(BuildOperationScriptPlugin.java:63)
        at org.gradle.configuration.internal.DefaultUserCodeApplicationContext.apply(DefaultUserCodeApplicationContext.java:48)
        at org.gradle.configuration.BuildOperationScriptPlugin.apply(BuildOperationScriptPlugin.java:63)
        at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:41)
        at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:26)
        at org.gradle.configuration.project.ConfigureActionsProjectEvaluator.evaluate(ConfigureActionsProjectEvaluator.java:34)
        at org.gradle.configuration.project.LifecycleProjectEvaluator$EvaluateProject.run(LifecycleProjectEvaluator.java:105)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.configuration.project.LifecycleProjectEvaluator.evaluate(LifecycleProjectEvaluator.java:68)
        at org.gradle.api.internal.project.DefaultProject.evaluate(DefaultProject.java:687)
        at org.gradle.api.internal.project.DefaultProject.evaluate(DefaultProject.java:140)
        at org.gradle.execution.TaskPathProjectEvaluator.configure(TaskPathProjectEvaluator.java:35)
        at org.gradle.execution.TaskPathProjectEvaluator.configureHierarchy(TaskPathProjectEvaluator.java:60)
        at org.gradle.configuration.DefaultBuildConfigurer.configure(DefaultBuildConfigurer.java:41)
        at org.gradle.initialization.DefaultGradleLauncher$ConfigureBuild.run(DefaultGradleLauncher.java:274)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.initialization.DefaultGradleLauncher.configureBuild(DefaultGradleLauncher.java:182)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:141)
        at org.gradle.initialization.DefaultGradleLauncher.executeTasks(DefaultGradleLauncher.java:124)
        at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:77)
        at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:74)
        at org.gradle.internal.work.DefaultWorkerLeaseService.withLocks(DefaultWorkerLeaseService.java:154)
        at org.gradle.internal.work.StopShieldingWorkerLeaseService.withLocks(StopShieldingWorkerLeaseService.java:38)
        at org.gradle.internal.invocation.GradleBuildController.doBuild(GradleBuildController.java:96)
        at org.gradle.internal.invocation.GradleBuildController.run(GradleBuildController.java:74)
        at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
        at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
        at org.gradle.tooling.internal.provider.ValidatingBuildActionRunner.run(ValidatingBuildActionRunner.java:32)
        at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner$3.run(RunAsBuildOperationBuildActionRunner.java:50)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner.run(RunAsBuildOperationBuildActionRunner.java:45)
        at org.gradle.tooling.internal.provider.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:51)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecuter.java:47)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecuter.java:44)
        at org.gradle.composite.internal.DefaultRootBuildState.run(DefaultRootBuildState.java:79)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:44)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
        at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:39)
        at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:25)
        at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:80)
        at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:53)
        at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:62)
        at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:34)
        at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:36)
        at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:25)
        at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:43)
        at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:29)
        at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:59)
        at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:31)
        at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:59)
        at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:44)
        at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:46)
        at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:30)
        at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:67)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
        at org.gradle.util.Swapper.swap(Swapper.java:38)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.LogAndCheckHealth.execute(LogAndCheckHealth.java:55)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:62)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:81)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
        at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:295)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: groovy.lang.MissingPropertyException: Could not get unknown property 'com' for root project 'zift-version-plugin-test' of type org.gradle.api.Project.
        at org.gradle.internal.metaobject.AbstractDynamicObject.getMissingProperty(AbstractDynamicObject.java:83)
        at org.gradle.groovy.scripts.BasicScript$ScriptDynamicObject.getMissingProperty(BasicScript.java:155)
        at org.gradle.internal.metaobject.AbstractDynamicObject.getProperty(AbstractDynamicObject.java:61)
        at org.gradle.groovy.scripts.BasicScript.getProperty(BasicScript.java:64)
        at build_cwttcu84eq7hpuu438ujk6vq7.run(/Users/cfouts/git-repos/zift/zift-version-plugin-test/build.gradle:15)
        at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:90)
        ... 102 more

Answer 1

You need to either supply the actual plugin class or the plugin ID as a String. So try changing it to either apply plugin: com.zift.utilities.ZiftVersionPlugin or apply plugin: "com.zift.utilities". You could also use a plugins block like this: plugins { id "com.zift.utilities" }.

Also, you can get rid of some boiler plate code if you use the Gradle Plugin Development Plugin. For instance, it can create the com.zift.utilities.properties file for you.