Checkstyle task can no longer be configured to analyse single files

[davidburstrom]

Expected Behavior

In Gradle 6.1 it was still possible to configure a Checkstyle task to analyse a single file using e.g.

        project.tasks.create(name: 'checkstyleGradle', type: Checkstyle) { Checkstyle task ->
            task.group = 'verification'
            task.description = 'Run Checkstyle on the Gradle build script'
            task.source = ['build.gradle']
            task.classpath = project.files()
        }

Current Behavior

In Gradle 6.2, the build fails with

Caused by: : /project/build.gradle is not a directory.
        at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:518)
        at com.puppycrawl.tools.checkstyle.ant.CheckstyleAntTask.scanFileSets(CheckstyleAntTask.java:560)
        at com.puppycrawl.tools.checkstyle.ant.CheckstyleAntTask.getFilesToCheck(CheckstyleAntTask.java:490)
        at com.puppycrawl.tools.checkstyle.ant.CheckstyleAntTask.processFiles(CheckstyleAntTask.java:333)
        at com.puppycrawl.tools.checkstyle.ant.CheckstyleAntTask.realExecute(CheckstyleAntTask.java:315)
        at com.puppycrawl.tools.checkstyle.ant.CheckstyleAntTask.execute(CheckstyleAntTask.java:287)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:292)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:99)
        at org.gradle.api.internal.project.ant.BasicAntBuilder.nodeCompleted(BasicAntBuilder.java:80)
        at org.gradle.internal.metaobject.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:483)
        at org.gradle.internal.metaobject.BeanDynamicObject.tryInvokeMethod(BeanDynamicObject.java:195)
        at org.gradle.internal.metaobject.AbstractDynamicObject.invokeMethod(AbstractDynamicObject.java:162)
        at org.gradle.api.internal.project.antbuilder.AntBuilderDelegate.nodeCompleted(AntBuilderDelegate.java:124)
        at org.gradle.api.plugins.quality.internal.CheckstyleInvoker$_invoke_closure1.doCall(CheckstyleInvoker.groovy:58)
        at org.gradle.util.ClosureBackedAction.execute(ClosureBackedAction.java:71)
        at org.gradle.util.ClosureBackedAction.execute(ClosureBackedAction.java:52)
        at org.gradle.api.internal.project.antbuilder.DefaultIsolatedAntBuilder$2.execute(DefaultIsolatedAntBuilder.java:154)
        at org.gradle.api.internal.project.antbuilder.DefaultIsolatedAntBuilder$2.execute(DefaultIsolatedAntBuilder.java:136)
        at org.gradle.api.internal.project.antbuilder.ClassPathToClassLoaderCache.withCachedClassLoader(ClassPathToClassLoaderCache.java:135)
        at org.gradle.api.internal.project.antbuilder.DefaultIsolatedAntBuilder.execute(DefaultIsolatedAntBuilder.java:130)
        at org.gradle.api.internal.project.IsolatedAntBuilder$execute$0.call(Unknown Source)
        at org.gradle.api.plugins.quality.internal.CheckstyleInvoker.invoke(CheckstyleInvoker.groovy:51)
        at org.gradle.api.plugins.quality.Checkstyle.run(Checkstyle.java:151)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:104)

The workaround to use

task.source = project.fileTree(dir: '.', include: 'build.gradle')

should have been fine, but in a very large repository, the task spends minutes just to scan the directories before finally analysing the one file requested.

Context

6.1 worked, 6.2 no longer works.

The result is that it is harder for us to maintain code standards in build scripts.

Steps to Reproduce

Run gradle (6.2) in a directory with a build.gradle file with the following contents

import org.gradle.api.plugins.quality.Checkstyle

plugins {
    id 'checkstyle'
}

dependencies {
    repositories {
        mavenCentral()
    }   
}

tasks.create(name: 'checkstyleGradle', type: Checkstyle) { Checkstyle task ->
    task.group = 'verification'
    task.description = 'Run Checkstyle on the Gradle build script'
    task.source = ['build.gradle']
    task.classpath = project.files()
    task.config = project.resources.text.fromString('<?xml version="1.0"?><!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN" "https://checkstyle.org/dtds/configuration_1_3.dtd"><module name="Checker"/>')
}

Your Environment

MacOS X 10.14.6
Build scan URL: N/A

[mateuszkwiecinski]

I'm experiencing exactly the same issue (on 6.2 only), but I'm able to reproduce it even when passing set of files, regardles of their number.
And I confirm workaround posted above works in my case too.

[davidburstrom]

@adammurdoch I saw a rather similar issue locally but for pmd. Is it reasonable to assume your fix addressed all regressions related to explicit files?

[ljacomet]

Yes that should be the case. If not, please file another issue.