Android: Compilation error with v7 support lib 27.1.0 "Program type already present" android.support.v7.recyclerview.extensions.ListAdapter

Question

I think there must be a bug with the 27.1.0 v7 support lib, just released. After updating my project to use it (from 26.1.0), I keep getting this compilation error:

Task :app:transformDexArchiveWithDexMergerForRegularDebug FAILED D8 is used to merge dex. Program type already present: android.support.v7.recyclerview.extensions.ListAdapter

FAILURE: Build failed with an exception.

• What went wrong: Execution failed for task ':app:transformDexArchiveWithDexMergerForRegularDebug'. com.android.build.api.transform.TransformException: com.android.tools.r8.errors.CompilationError: Program type already present: android.support.v7.recyclerview.extensions.ListAdapter

• Try: Run with --info or --debug option to get more log output.

• Exception is: org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformDexArchiveWithDexMergerForRegularDebug'. at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70) at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51) at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62) at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54) at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:60) at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:97) at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:87) at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:52) at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52) at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54) at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43) at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34) at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:248) at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336) at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328) at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199) at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110) at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:241) at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:230) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:123) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:79) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:104) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:98) at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:626) at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:581) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:98) 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: java.lang.RuntimeException: com.android.build.api.transform.TransformException: com.android.tools.r8.errors.CompilationError: Program type already present: android.support.v7.recyclerview.extensions.ListAdapter at com.android.builder.profile.Recorder$Block.handleException(Recorder.java:55) at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:104) at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:213) at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73) at org.gradle.api.internal.project.taskfactory.IncrementalTaskAction.doExecute(IncrementalTaskAction.java:46) at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:39) at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:26) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:121) at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336) at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328) at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199) at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:110) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:92) ... 29 more Caused by: com.android.build.api.transform.TransformException: com.android.tools.r8.errors.CompilationError: Program type already present: android.support.v7.recyclerview.extensions.ListAdapter at com.android.build.gradle.internal.transforms.DexMergerTransform.transform(DexMergerTransform.java:230) at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:222) at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:218) at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:102) ... 41 more Caused by: com.android.tools.r8.errors.CompilationError: Program type already present: android.support.v7.recyclerview.extensions.ListAdapter at com.android.tools.r8.utils.ProgramClassCollection.resolveClassConflictImpl(ProgramClassCollection.java:61) at com.android.tools.r8.utils.ProgramClassCollection.lambda$create$0(ProgramClassCollection.java:22) at com.android.tools.r8.utils.ProgramClassCollection.create(ProgramClassCollection.java:22) at com.android.tools.r8.graph.DexApplication$Builder.build(DexApplication.java:408) at com.android.tools.r8.dex.ApplicationReader.read(ApplicationReader.java:96) at com.android.tools.r8.D8.runForTesting(D8.java:179) at com.android.tools.r8.D8.runForTesting(D8.java:152) at com.android.tools.r8.D8.run(D8.java:71) at com.android.builder.dexing.D8DexArchiveMerger.mergeDexArchives(D8DexArchiveMerger.java:73) at com.android.build.gradle.internal.transforms.DexMergerTransformCallable.call(DexMergerTransformCallable.java:97) at com.android.build.gradle.internal.transforms.DexMergerTransformCallable.call(DexMergerTransformCallable.java:35)

I have looked at my project's dependencies (with ./gradlew :<module>:dependencies [where <module> is all my modules]) and verified that I have only one dependency that should be pulling in the support ListAdapter class, and it is this one:

implementation "com.android.support:recyclerview-v7:27.1.0"

I also use

configurations.all {
    resolutionStrategy {
        ...
        force "com.android.support:recyclerview-v7:27.1.0"
    }
}

I have tried cleaning/rebuilding. I have tried invalidating caches and restarting. I have also tried manually deleting all my build folders and .gradle folders. I have also tried disabling D8, but then my build just hangs forever. The problem persists. I'm not even using ListAdapter!

Answer 1

Figured it out! Turns out the android.arch.paging:runtime-1.0.0-alpha4-1 dependency also had ListAdapter declared. After updating the paging lib to alpha6, the problem was resolved.

EDIT For some reason, this question is getting a lot of attention! So, I thought I'd add this comment as a "teach a person to fish" sort of moment. The question: how did I figure out where my ListAdapters were coming from? The answer? If you're using Android Studio / IntelliJ IDEA, hit ctrl+n to begin searching for class names. You'll see this dialog:

Please note the checkbox! If you don't have that checked, you will never find a class included by a library. With it checked, it'll show the provenance of every class in your project.