Zachs-MBP:SpotbugsExample Zach$ ./gradlew spotbugs --stacktrace

FAILURE: Build failed with an exception.

* What went wrong:
Error while evaluating property 'allSource' of task ':app:spotbugs'
> path may not be null or empty string. path='null'

* Try:
Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Exception is:
org.gradle.api.InvalidUserDataException: Error while evaluating property 'allSource' of task ':app:spotbugs'
        at org.gradle.api.internal.tasks.properties.GetInputPropertiesVisitor$1.create(GetInputPropertiesVisitor.java:58)
        at org.gradle.api.internal.tasks.properties.GetInputPropertiesVisitor$1.create(GetInputPropertiesVisitor.java:48)
        at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository.snapshotTaskInputProperties(CacheBackedTaskHistoryRepository.java:303)
        at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository.createExecution(CacheBackedTaskHistoryRepository.java:146)
        at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository.access$100(CacheBackedTaskHistoryRepository.java:61)
        at org.gradle.api.internal.changedetection.state.CacheBackedTaskHistoryRepository$1.getCurrentExecution(CacheBackedTaskHistoryRepository.java:111)
        at org.gradle.api.internal.changedetection.changes.DefaultTaskArtifactStateRepository$TaskArtifactStateImpl.getStates(DefaultTaskArtifactStateRepository.java:208)
        at org.gradle.api.internal.changedetection.changes.DefaultTaskArtifactStateRepository$TaskArtifactStateImpl.isUpToDate(DefaultTaskArtifactStateRepository.java:93)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:50)
        at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:101)
        at org.gradle.api.internal.tasks.execution.FinalizeInputFilePropertiesTaskExecuter.execute(FinalizeInputFilePropertiesTaskExecuter.java:44)
        at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:91)
        at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:62)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:256)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor$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:249)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:238)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$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$1.execute(DefaultTaskPlanExecutor.java:98)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:663)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:597)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$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.IllegalArgumentException: path may not be null or empty string. path='null'
        at org.gradle.api.internal.file.AbstractBaseDirFileResolver.doResolve(AbstractBaseDirFileResolver.java:65)
        at org.gradle.api.internal.file.AbstractFileResolver.resolve(AbstractFileResolver.java:85)
        at org.gradle.api.internal.file.AbstractFileResolver.resolve(AbstractFileResolver.java:67)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext$FileCollectionConverter.convertInto(DefaultFileCollectionResolveContext.java:188)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext.doResolve(DefaultFileCollectionResolveContext.java:143)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext.resolveAsFileCollections(DefaultFileCollectionResolveContext.java:95)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext$FileCollectionConverter.convertInto(DefaultFileCollectionResolveContext.java:172)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext.doResolve(DefaultFileCollectionResolveContext.java:112)
        at org.gradle.api.internal.file.collections.DefaultFileCollectionResolveContext.resolveAsFileCollections(DefaultFileCollectionResolveContext.java:95)
        at org.gradle.api.internal.file.CompositeFileCollection.getSourceCollections(CompositeFileCollection.java:172)
        at org.gradle.api.internal.file.CompositeFileCollection.getFiles(CompositeFileCollection.java:55)
        at org.gradle.api.internal.tasks.properties.GetInputPropertiesVisitor.prepareValue(GetInputPropertiesVisitor.java:74)
        at org.gradle.api.internal.tasks.properties.GetInputPropertiesVisitor.access$100(GetInputPropertiesVisitor.java:34)
        at org.gradle.api.internal.tasks.properties.GetInputPropertiesVisitor$1.create(GetInputPropertiesVisitor.java:55)
        ... 35 more


* Get more help at https://help.gradle.org

BUILD FAILED in 0s
1 actionable task: 1 executed

apply plugin: 'com.android.application'
apply plugin: 'com.github.spotbugs'

buildscript {
    repositories {
        maven { url 'https://plugins.gradle.org/m2/' }
    }

    dependencies {
        classpath 'gradle.plugin.com.github.spotbugs:spotbugs-gradle-plugin:1.6.8'
    }
}

spotbugs {
    toolVersion = '3.1.10'
}

task spotbugs (type: com.github.spotbugs.SpotBugsTask) {
    ignoreFailures = true
    effort = 'max'
    reportLevel = 'high'

    classes = files("${project.buildDir}/intermediates/javac")
    source = 'src'
    classpath = files()

    reports {
        xml.enabled = false
        html.enabled = true
        html.destination = file("$project.buildDir/outputs/spotbugs/spotbugs.html")
    }
}

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.zach.spotbugsexample"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}