fix: unnecessary targetFolder directory creation and unnecessary transformation to string

Author: bric3

buildSrc/src/main/kotlin/datadog/gradle/plugin/csi/CallSiteInstrumentationExtension.kt

@@ -40,7 +40,7 @@ abstract class CallSiteInstrumentationExtension @Inject constructor(
    * The location to generate call site source code ({@code <project>/build/generated/sources/csi} by default).
    */
   val targetFolder: DirectoryProperty = objectFactory.directoryProperty().convention(
-    layout.buildDirectory.dir("generated${File.separatorChar}sources${File.separatorChar}csi")
+    layout.buildDirectory.dir("generated/sources/$CSI_SOURCE_SET")
   )
 
   /**

buildSrc/src/main/kotlin/datadog/gradle/plugin/csi/CallSiteInstrumentationPlugin.kt

@@ -17,6 +17,7 @@ import org.gradle.api.tasks.SourceSet.TEST_SOURCE_SET_NAME
 import org.gradle.api.tasks.SourceSetContainer
 import org.gradle.api.tasks.TaskProvider
 import org.gradle.api.tasks.compile.AbstractCompile
+import org.gradle.internal.configuration.problems.projectPathFrom
 import org.gradle.jvm.tasks.Jar
 import org.gradle.jvm.toolchain.JavaToolchainService
 import org.gradle.kotlin.dsl.apply
@@ -33,8 +34,8 @@ import java.util.Locale
 import javax.inject.Inject
 
 private const val CALL_SITE_INSTRUMENTER_MAIN_CLASS = "datadog.trace.plugin.csi.PluginApplication"
-private const val CSI = "csi"
-private const val CSI_SOURCE_SET = CSI
+const val CSI = "csi"
+const val CSI_SOURCE_SET = CSI
 
 abstract class CallSiteInstrumentationPlugin : Plugin<Project> {
   @get:Inject
@@ -52,13 +53,12 @@ abstract class CallSiteInstrumentationPlugin : Plugin<Project> {
 
   private fun configureSourceSets(project: Project, extension: CallSiteInstrumentationExtension) {
     // create a new source set for the csi files
-    val targetFolder = newBuildFolder(project, extension.targetFolder.get().asFile.toString())
     val sourceSets = project.sourceSets
     val mainSourceSet = sourceSets.named(MAIN_SOURCE_SET_NAME).get()
     val csiSourceSet = sourceSets.create(CSI_SOURCE_SET) {
       compileClasspath += mainSourceSet.output // mainly needed for the plugin tests
       annotationProcessorPath += mainSourceSet.annotationProcessorPath
-      java.srcDir(targetFolder)
+      java.srcDir(extension.targetFolder)
     }
 
     project.configurations.named(csiSourceSet.compileClasspathConfigurationName) {
@@ -83,16 +83,6 @@ abstract class CallSiteInstrumentationPlugin : Plugin<Project> {
     }
   }
 
-  private fun newBuildFolder(project: Project, name: String): File {
-    val folder = project.layout.buildDirectory.dir(name).get().asFile
-    if (!folder.exists()) {
-      if (!folder.mkdirs()) {
-        throw GradleException("Cannot create folder $folder")
-      }
-    }
-    return folder
-  }
-
   private fun newTempFile(folder: File, name: String): File {
     val file = File(folder, name)
     if (!file.exists() && !file.createNewFile()) {