feature add detektAnalysis task

gradle/plugins/src/main/java/static_analysis/linters/DetektLinter.kt

@@ -2,15 +2,24 @@ package static_analysis.linters
 
 import io.gitlab.arturbosch.detekt.Detekt
 import org.gradle.api.Project
+import org.gradle.api.file.FileTree
 import static_analysis.errors.DetektError
 import static_analysis.errors.StaticAnalysisError
 import static_analysis.plugins.StaticAnalysisExtension
 import static_analysis.utils.getSources
+import static_analysis.utils.runCommand
 import static_analysis.utils.typedChildren
 import static_analysis.utils.xmlParser
+import java.io.File
 
 class DetektLinter : Linter {
 
+    private companion object {
+        const val TAG = "DetektLinter"
+        const val ONLY_DIFFS_FLAG = "only-diffs"
+        const val GET_GIT_DIFFS_COMMAND = "git diff --name-only --ignore-submodules"
+    }
+
     override val name: String = "Detekt"
 
     override fun getErrors(project: Project): List<StaticAnalysisError> = xmlParser(project.getDetektReportFile())
@@ -50,11 +59,39 @@ class DetektLinter : Linter {
                     }
                 }
 
-                source = getSources(extension.excludes)
+                val diffsBranch = properties[ONLY_DIFFS_FLAG] as? String
+                source = getSources(extension.excludes, diffsBranch, project)
             }
         }
     }
 
+    private fun getSources(excludes: String, diffsBranch: String?, project: Project): FileTree = when (diffsBranch) {
+        null -> project.getSources(excludes)
+        else -> getGitDiffFiles(excludes, diffsBranch, project)
+    }
+
+    private fun getGitDiffFiles(excludes: String, diffsBranch: String, project: Project): FileTree {
+        val getGitDiffsCommand = if (diffsBranch.isEmpty()) {
+            GET_GIT_DIFFS_COMMAND
+        } else {
+            GET_GIT_DIFFS_COMMAND.plus(" --merge-base $diffsBranch")
+        }
+
+        val gitDiffs = getGitDiffsCommand.runCommand()
+
+        if (gitDiffs.isNullOrEmpty()) {
+            project.logger.error("$TAG: Diffs are empty or specified branch or commit does not exists")
+            return project.files().asFileTree
+        }
+
+        val diffFiles = gitDiffs.lines()
+                .map { File(it) }
+                .filter { (it.extension == "kt" || it.extension == "java") && !excludes.contains(it.path) }
+                .toList()
+
+        return project.files(diffFiles).asFileTree
+    }
+
     override fun getTaskNames(project: Project, buildType: String?): List<String> = listOf(":detekt")
 
     private fun Project.getDetektReportFile() = file("${rootProject.buildDir}/reports/detekt.xml")

gradle/plugins/src/main/java/static_analysis/plugins/StaticAnalysisAndroidPlugin.kt

@@ -27,6 +27,23 @@ class StaticAnalysisAndroidPlugin : StaticAnalysisPlugin() {
                                 buildVariant = applicationVariants.first { it.name.contains("Debug") }.name
                         )
                     }
+                    /**
+                     *  Task to run detekt checks.
+                     *
+                     * @param --only-diffs <branch or commit> if specified, only files modified
+                     * relative to this branch or commit will be checked. If specified without value
+                     * then current uncommited changes will be checked. If not specified all source files will be checked.
+                     * @see DetektLinter.getGitDiffFiles, 'git diff' for more info.
+                     * */
+                    project.tasks.register("detektAnalysis") {
+                        val detektLinter = linters.find { it is DetektLinter }
+                                ?: throw IllegalStateException("DetektLinter not found")
+
+                        setupStaticAnalysisTask(
+                                linters = listOf(detektLinter),
+                                buildVariant = applicationVariants.first { it.name.contains("Debug") }.name
+                        )
+                    }
                 }
             }
         }

gradle/plugins/src/main/java/static_analysis/utils/String.kt

@@ -0,0 +1,25 @@
+package static_analysis.utils
+
+import java.io.File
+import java.io.IOException
+import java.util.concurrent.TimeUnit
+
+fun String.runCommand(
+        directoryToExecute: File? = null,
+        timeoutSec: Long = 30,
+): String? {
+    return try {
+        val parts = this.split("\\s".toRegex())
+        val process = ProcessBuilder(*parts.toTypedArray())
+                .directory(directoryToExecute)
+                .redirectOutput(ProcessBuilder.Redirect.PIPE)
+                .redirectError(ProcessBuilder.Redirect.PIPE)
+                .start()
+
+        process.waitFor(timeoutSec, TimeUnit.SECONDS)
+        process.inputStream.bufferedReader().readText()
+    } catch(e: IOException) {
+        e.printStackTrace()
+        null
+    }
+}