update checkstyle to 10.1: as checkstyle 10 drops java 8 support, aut…

…omatically switch to backport (maintained by the community) on jre lower 11;

 add new configuration quality.checkstyleBackport to be able to force backport for jre 11 or disable automatic switching to backport

CHANGELOG.md

@@ -1,3 +1,13 @@
+* Update checkstyle 9.1 -> 10.1
+  IMPORTANT: Checkstyle 10 requires java 11, but plugin will automatically switch to
+  [backports](https://checkstyle.org/#Backport) for lower jre.
+    Additional maven repository would be registered if required (LIMITED to checkstyle only)
+    Warning in log would clearly indicate when backport is used   
+* New option: quality.checkstyleBackport (by default true for jre < 11)
+    Option might be used to force backport for java >=11 or to disable backport at all
+* Update checkstyle config:
+    - Add [UnusedLocalVariable](https://checkstyle.sourceforge.io/config_coding.html#UnusedLocalVariable)
+
 ### 4.7.0 (2021-11-10)
 * Fix gradle 7 deprecation warnings (#30)
 * Update spotbugs plugin 4.7.1 -> 4.7.9

build.gradle

@@ -55,7 +55,7 @@ mkdocs {
     }
     extras = [
             'version': project.docVersion,
-            'checkstyle': '9.1',
+            'checkstyle': '10.1',
             'pmd': '6.34.0',
             'spotbugs': '4.4.2',
             'codenarc': '2.2.0',

src/main/groovy/ru/vyarus/gradle/plugin/quality/QualityExtension.groovy

@@ -2,6 +2,7 @@ package ru.vyarus.gradle.plugin.quality
 
 import groovy.transform.CompileStatic
 import groovy.transform.TypeCheckingMode
+import org.gradle.api.JavaVersion
 import org.gradle.api.Project
 import org.gradle.api.file.FileCollection
 import org.gradle.api.tasks.SourceSet
@@ -21,7 +22,7 @@ class QualityExtension {
         sourceSets = [project.sourceSets.main] as Collection<SourceSet>
     }
 
-    String checkstyleVersion = '9.1'
+    String checkstyleVersion = '10.1'
     String pmdVersion = '6.34.0'
     String spotbugsVersion = '4.4.2'
     String codenarcVersion = '2.2.0'
@@ -79,6 +80,21 @@ class QualityExtension {
      */
     boolean codenarc = true
 
+    /**
+     * Since checkstyle 10, minimum required java is 11. Community (not checkstyle core team!) started a
+     * <a href="https://checkstyle.org/#Backport">backport</a> project - maintaining java 8 compatibility.
+     * Backport releases would be delayed relative to main checkstyle releases (see
+     * <a href="https://rnveach.github.io/checkstyle-backport-jre8/">checkstyle-backport-jre8</a>).
+     * <p>
+     * NOTE: additional repository would be configured to download backport (only when backport required). But the
+     * repository would be limited to checkstyle group only!
+     * <p>
+     * This property switches between backport and normal checkstyle versions. By default backport would be enabled
+     * on java 8-10, but you can manually enable it for all java versions if required. Or you can use false value
+     * to prevent backport behaviour and preventing new  repository registration.
+     */
+    boolean checkstyleBackport = !JavaVersion.current().java11Compatible
+
     /**
      * Enable PMD incremental analysis (cache results between builds to speed up processing).
      * This is a shortcut for pmd plugin's {@code pmd.incrementalAnalysis } configuration option.

src/main/groovy/ru/vyarus/gradle/plugin/quality/QualityPlugin.groovy

@@ -9,7 +9,13 @@ import org.gradle.api.Task
 import org.gradle.api.execution.TaskExecutionGraph
 import org.gradle.api.plugins.GroovyPlugin
 import org.gradle.api.plugins.JavaPlugin
-import org.gradle.api.plugins.quality.*
+import org.gradle.api.plugins.quality.Checkstyle
+import org.gradle.api.plugins.quality.CheckstylePlugin
+import org.gradle.api.plugins.quality.CodeNarc
+import org.gradle.api.plugins.quality.CodeNarcPlugin
+import org.gradle.api.plugins.quality.Pmd
+import org.gradle.api.plugins.quality.PmdExtension
+import org.gradle.api.plugins.quality.PmdPlugin
 import org.gradle.api.reporting.Report
 import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.SourceTask
@@ -18,7 +24,13 @@ import org.gradle.api.tasks.TaskState
 import org.gradle.api.tasks.compile.JavaCompile
 import org.gradle.process.CommandLineArgumentProvider
 import org.gradle.util.GradleVersion
-import ru.vyarus.gradle.plugin.quality.report.*
+import ru.vyarus.gradle.plugin.quality.report.CheckstyleReporter
+import ru.vyarus.gradle.plugin.quality.report.CodeNarcReporter
+import ru.vyarus.gradle.plugin.quality.report.CpdReporter
+import ru.vyarus.gradle.plugin.quality.report.HtmlReportGenerator
+import ru.vyarus.gradle.plugin.quality.report.PmdReporter
+import ru.vyarus.gradle.plugin.quality.report.Reporter
+import ru.vyarus.gradle.plugin.quality.report.SpotbugsReporter
 import ru.vyarus.gradle.plugin.quality.spotbugs.CustomSpotBugsPlugin
 import ru.vyarus.gradle.plugin.quality.task.InitQualityConfigTask
 import ru.vyarus.gradle.plugin.quality.util.CpdUtils
@@ -121,6 +133,7 @@ class QualityPlugin implements Plugin<Project> {
     }
 
     @CompileStatic(TypeCheckingMode.SKIP)
+    @SuppressWarnings(['MethodSize', 'NestedBlockDepth'])
     private void applyCheckstyle(Project project, QualityExtension extension, ConfigLoader configLoader,
                                  boolean register) {
         configurePlugin(project,
@@ -141,6 +154,19 @@ class QualityPlugin implements Plugin<Project> {
                     configDirectory = configLoader.resolveCheckstyleConfigDir()
                     sourceSets = extension.sourceSets
                 }
+                if (extension.checkstyleBackport) {
+                    repositories {
+                        maven {
+                            url 'https://rnveach.github.io/checkstyle-backport-jre8/'
+                            // use custom repository ONLY for checkstyle (just in case)
+                            content { includeGroup 'com.puppycrawl.tools' }
+                        }
+                    }
+                    dependencies {
+                        checkstyle "com.puppycrawl.tools:checkstyle-backport-jre8:${extension.checkstyleVersion}"
+                    }
+                }
+
                 tasks.withType(Checkstyle).configureEach {
                     doFirst {
                         if (GradleVersion.current() < GradleVersion.version('6.0')) {
@@ -150,6 +176,10 @@ class QualityPlugin implements Plugin<Project> {
                             configProperties[propName] = configProperties[propName]
                                     ?: configLoader.resolveCheckstyleConfigDir().absolutePath
                         }
+                        if (extension.checkstyleBackport) {
+                            project.logger.warn("WARNING: checkstyle-backport-jre8 (${extension.checkstyleVersion})" +
+                                    ' used instead of regular checkstyle: https://checkstyle.org/#Backport')
+                        }
                         configLoader.resolveCheckstyleConfig()
                         applyExcludes(it, extension)
                     }

src/main/resources/ru/vyarus/quality/config/checkstyle/checkstyle.xml

@@ -128,6 +128,7 @@
         <module name="UnnecessarySemicolonAfterTypeMemberDeclaration"/>
         <module name="UnnecessarySemicolonInEnumeration"/>
         <module name="UnnecessarySemicolonInTryWithResources"/>
+        <module name="UnusedLocalVariable"/>
         <module name="VariableDeclarationUsageDistance">
             <property name="allowedDistance" value="5"/>
         </module>

src/test/groovy/ru/vyarus/gradle/plugin/quality/MultiModuleUseKitTest.groovy

@@ -41,7 +41,10 @@ class MultiModuleUseKitTest extends AbstractKitTest {
         BuildResult result = run('check')
 
         then: "violations detected in module only"
-        unifyString(result.output).replaceAll("Total time: .*", "").trim().startsWith("""> Task :mod1:compileJava
+        unifyString(result.output).replaceAll("Total time: .*", "")
+                // only on jdk 8
+                .replaceAll("WARNING: checkstyle-backport-jre8 .*\n", "")
+                .trim().startsWith("""> Task :mod1:compileJava
 > Task :mod1:processResources NO-SOURCE
 > Task :mod1:classes