Feature. Enable confiuring of ktlint reporter in gradle plugin (#724)

* feature/gradle-ktlint-reporter(#714)

### What's done:
  * Logic done
  * Added tests

README.md

@@ -137,6 +137,30 @@ diktat {
 }
 ```
 
+Also `diktat` extension has different reporters. You can specify `json`, `html`, `checkstyle`, `plain` (default) or your own custom reporter:
+```kotlin
+diktat {
+    reporter = "json" // "html", "checkstyle", "plain"
+}
+```
+
+Example of your custom reporter:
+```kotlin
+diktat {
+    reporter = "custom:name:pathToJar"
+}
+```
+Name parameter is the name of your reporter and as the last parameter you should specify path to jar, which contains your reporter.
+[Example of the junit custom reporter.](https://github.com/kryanod/ktlint-junit-reporter)
+
+You can also specify an output. 
+```kotlin
+diktat {
+    reporter = "json"
+    output = "someFile.json"
+}
+```
+
 You can run diktat checks using task `diktatCheck` and automatically fix errors with tasks `diktatFix`.
 
 ## Customizations via `diktat-analysis.yml`

diktat-gradle-plugin/build.gradle.kts

@@ -29,7 +29,6 @@ dependencies {
     implementation("com.pinterest.ktlint:ktlint-core:$ktlintVersion") {
         exclude("com.pinterest.ktlint", "ktlint-ruleset-standard")
     }
-    implementation("com.pinterest.ktlint:ktlint-reporter-plain:$ktlintVersion")
     implementation("org.cqfn.diktat:diktat-rules:$diktatVersion")
 
     testImplementation("org.junit.jupiter:junit-jupiter-api:$junitVersion")

diktat-gradle-plugin/src/functionalTest/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePluginFunctionalTest.kt

@@ -4,6 +4,7 @@ import org.cqfn.diktat.plugin.gradle.DiktatGradlePlugin.Companion.DIKTAT_CHECK_T
 import org.gradle.buildinit.plugins.internal.modifiers.BuildInitDsl
 import org.gradle.internal.impldep.org.junit.rules.TemporaryFolder
 import org.gradle.testkit.runner.TaskOutcome
+import org.jetbrains.kotlin.com.intellij.util.ObjectUtils.assertNotNull
 import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Assertions
 import org.junit.jupiter.api.BeforeEach
@@ -39,6 +40,28 @@ class DiktatGradlePluginFunctionalTest {
         )
     }
 
+    @Test
+    fun `should have json reporter files`() {
+        buildFile.appendText(
+            """${System.lineSeparator()}
+                diktat {
+                    inputs = files("src/**/*.kt")
+                    reporterType = "json"
+                    output = "test.txt"
+                }
+            """.trimIndent()
+        )
+        val result = runDiktat(testProjectDir, shouldSucceed = false)
+
+        val diktatCheckBuildResult = result.task(":$DIKTAT_CHECK_TASK")
+        requireNotNull(diktatCheckBuildResult)
+        Assertions.assertEquals(TaskOutcome.FAILED, diktatCheckBuildResult.outcome)
+        val file = assertNotNull(testProjectDir.root.walkTopDown().filter { it.name == "test.txt" }.first())
+        Assertions.assertTrue(
+                file.readLines().any { it.contains("[HEADER_MISSING_OR_WRONG_COPYRIGHT]") }
+        )
+    }
+
     @Test
     fun `should execute diktatCheck with explicit inputs`() {
         buildFile.appendText(

diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatExtension.kt

@@ -1,6 +1,5 @@
 package org.cqfn.diktat.plugin.gradle
 
-import com.pinterest.ktlint.core.Reporter
 import org.gradle.api.file.FileCollection
 import java.io.File
 
@@ -18,6 +17,17 @@ open class DiktatExtension {
      */
     var debug = false
 
+    /**
+     * Type of the reporter to use
+     */
+    var reporterType: String = "plain"
+
+    /**
+     * Type of output
+     * Default: System.out
+     */
+    var output: String = ""
+
     /**
      * Path to diktat yml config file. Can be either absolute or relative to project's root directory.
      * Default value: `diktat-analysis.yml` in rootDir.
@@ -29,12 +39,6 @@ open class DiktatExtension {
      */
     lateinit var excludes: FileCollection
 
-    /**
-     * Ktlint's [Reporter] which will be used during run.
-     * Private until I find a way to configure it.
-     */
-    internal lateinit var reporter: Reporter
-
     /**
      * Paths that will be scanned for .kt(s) files
      */

diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePlugin.kt

@@ -1,6 +1,5 @@
 package org.cqfn.diktat.plugin.gradle
 
-import com.pinterest.ktlint.reporter.plain.PlainReporter
 import generated.DIKTAT_VERSION
 import generated.KTLINT_VERSION
 import org.gradle.api.Plugin
@@ -22,7 +21,6 @@ class DiktatGradlePlugin : Plugin<Project> {
             }
             diktatConfigFile = project.rootProject.file("diktat-analysis.yml")
             excludes = project.files()
-            reporter = PlainReporter(System.out)
         }
 
         // only gradle 7+ (or maybe 6.8) will embed kotlin 1.4+, kx.serialization is incompatible with kotlin 1.3, so until then we have to use JavaExec wrapper

diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskBase.kt

@@ -3,6 +3,7 @@ package org.cqfn.diktat.plugin.gradle
 import org.cqfn.diktat.plugin.gradle.DiktatGradlePlugin.Companion.DIKTAT_CHECK_TASK
 import org.cqfn.diktat.plugin.gradle.DiktatGradlePlugin.Companion.DIKTAT_FIX_TASK
 import org.cqfn.diktat.ruleset.rules.DIKTAT_CONF_PROPERTY
+import org.cqfn.diktat.ruleset.utils.log
 
 import generated.DIKTAT_VERSION
 import generated.KTLINT_VERSION
@@ -50,6 +51,10 @@ open class DiktatJavaExecTaskBase @Inject constructor(
         } else {
             main = "com.pinterest.ktlint.Main"
         }
+        // Plain, checkstyle and json reporter are provided out of the box in ktlint
+        if (diktatExtension.reporterType == "html") {
+            diktatConfiguration.dependencies.add(project.dependencies.create("com.pinterest.ktlint:ktlint-reporter-html:$KTLINT_VERSION"))
+        }
         classpath = diktatConfiguration
         project.logger.debug("Setting diktatCheck classpath to ${diktatConfiguration.dependencies.toSet()}")
         if (diktatExtension.debug) {
@@ -83,6 +88,8 @@ open class DiktatJavaExecTaskBase @Inject constructor(
             diktatExtension.excludes.files.forEach {
                 addPattern(it, negate = true)
             }
+
+            add(createReporterFlag(diktatExtension))
         }
         logger.debug("Setting JavaExec args to $args")
     }
@@ -107,6 +114,40 @@ open class DiktatJavaExecTaskBase @Inject constructor(
     @Suppress("FUNCTION_BOOLEAN_PREFIX")
     override fun getIgnoreFailures(): Boolean = ignoreFailuresProp.getOrElse(false)
 
+    private fun createReporterFlag(diktatExtension: DiktatExtension): String {
+        val flag: StringBuilder = StringBuilder()
+
+        // Plain, checkstyle and json reporter are provided out of the box in ktlint
+        when (diktatExtension.reporterType) {
+            "json" -> flag.append("--reporter=json")
+            "html" -> flag.append("--reporter=html")
+            "checkstyle" -> flag.append("--reporter=checkstyle")
+            else -> customReporter(diktatExtension, flag)
+        }
+
+        if (diktatExtension.output.isNotEmpty()) {
+            flag.append(",output=${diktatExtension.output}")
+        }
+
+        return flag.toString()
+    }
+
+    private fun customReporter(diktatExtension: DiktatExtension, flag: java.lang.StringBuilder) {
+        if (diktatExtension.reporterType.startsWith("custom")) {
+            val name = diktatExtension.reporterType.split(":")[1]
+            val jarPath = diktatExtension.reporterType.split(":")[2]
+            if (name.isEmpty() || jarPath.isEmpty()) {
+                log.warn("Either name or path to jar is not specified. Falling to plain reporter")
+                flag.append("--reporter=plain")
+            } else {
+                flag.append("--reporter=$name,artifact=$jarPath")
+            }
+        } else {
+            flag.append("--reporter=plain")
+            log.warn("Unknown reporter was specified. Falling back to plain reporter.")
+        }
+    }
+
     @Suppress("MagicNumber")
     private fun isMainClassPropertySupported(gradleVersionString: String) =
             GradleVersion.version(gradleVersionString) >= GradleVersion.version("6.4")

diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePluginTest.kt

@@ -32,4 +32,10 @@ class DiktatGradlePluginTest {
         Assertions.assertIterableEquals(project.fileTree("src").files, diktatExtension.inputs.files)
         Assertions.assertTrue(diktatExtension.inputs.files.isNotEmpty())
     }
+
+    @Test
+    fun `check that the right reporter dependency added`() {
+        val diktatExtension = project.extensions.getByName("diktat") as DiktatExtension
+        Assertions.assertTrue(diktatExtension.reporterType == "plain")
+    }
 }

diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskTest.kt

@@ -23,7 +23,7 @@ class DiktatJavaExecTaskTest {
     @Test
     fun `check command line for various inputs`() {
         assertCommandLineEquals(
-            listOf(null, combinePathParts("src", "**", "*.kt"))
+            listOf(null, combinePathParts("src", "**", "*.kt"), "--reporter=plain")
         ) {
             inputs = project.files("src/**/*.kt")
         }
@@ -32,7 +32,7 @@ class DiktatJavaExecTaskTest {
     @Test
     fun `check command line in debug mode`() {
         assertCommandLineEquals(
-            listOf(null, "--debug", combinePathParts("src", "**", "*.kt"))
+            listOf(null, "--debug", combinePathParts("src", "**", "*.kt"), "--reporter=plain")
         ) {
             inputs = project.files("src/**/*.kt")
             debug = true
@@ -43,7 +43,7 @@ class DiktatJavaExecTaskTest {
     fun `check command line with excludes`() {
         assertCommandLineEquals(
             listOf(null, combinePathParts("src", "**", "*.kt"),
-                "!${combinePathParts("src", "main", "kotlin", "generated")}"
+                "!${combinePathParts("src", "main", "kotlin", "generated")}", "--reporter=plain"
             )
         ) {
             inputs = project.files("src/**/*.kt")
@@ -76,6 +76,57 @@ class DiktatJavaExecTaskTest {
         Assertions.assertEquals(File(project.projectDir.parentFile, "diktat-analysis.yml").absolutePath, task.systemProperties[DIKTAT_CONF_PROPERTY])
     }
 
+    @Test
+    fun `check command line has reporter type and output`() {
+        assertCommandLineEquals(
+            listOf(null, "--reporter=json,output=some.txt")
+        ) {
+            inputs = project.files()
+            diktatConfigFile = project.file("../diktat-analysis.yml")
+            reporterType = "json"
+            output = "some.txt"
+        }
+    }
+
+    @Test
+    fun `check command line has reporter type without output`() {
+        assertCommandLineEquals(
+            listOf(null, "--reporter=json")
+        ) {
+            inputs = project.files()
+            diktatConfigFile = project.file("../diktat-analysis.yml")
+            reporterType = "json"
+        }
+    }
+
+    @Test
+    fun `check command line has custom reporter type with output`() {
+        assertCommandLineEquals(
+            listOf(null, "--reporter=customName,artifact=customPath")
+        ) {
+            inputs = project.files()
+            diktatConfigFile = project.file("../diktat-analysis.yml")
+            reporterType = "custom:customName:customPath"
+        }
+    }
+
+    @Test
+    fun `check that project has html dependency`() {
+        val task = project.registerDiktatTask {
+            inputs = project.files()
+            diktatConfigFile = project.file("../diktat-analysis.yml")
+            reporterType = "html"
+        }
+
+        Assertions.assertTrue(
+            project
+                .configurations
+                .getByName("diktat")
+                .dependencies
+                .any { it.name == "ktlint-reporter-html" })
+        Assertions.assertEquals(File(project.projectDir.parentFile, "diktat-analysis.yml").absolutePath, task.systemProperties[DIKTAT_CONF_PROPERTY])
+    }
+
     @Test
     fun `check system property with multiproject build with default config`() {
         setupMultiProject()