Timestamp work.

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt

@@ -112,7 +112,7 @@ abstract class JvmCompilerPlugin @Inject constructor(
                 it.exists()
             } .forEach {
                 log(2, "Copying from $sourceDirs to $absOutputDir")
-                KFiles.copyRecursively(it, absOutputDir, deleteFirst = true)
+                KFiles.copyRecursively(it, absOutputDir, deleteFirst = false)
             }
         } else {
             lp(project, "No resources to copy for $sourceSet")
@@ -133,7 +133,7 @@ abstract class JvmCompilerPlugin @Inject constructor(
         project.projectProperties.put(COMPILER_ARGS, arrayListOf(*args))
     }
 
-    fun isOutOfDate(project: Project, context: KobaltContext, actionInfo: CompilerActionInfo) : Boolean {
+    fun isOutdated(project: Project, context: KobaltContext, actionInfo: CompilerActionInfo) : Boolean {
         fun stripSourceDir(sourceFile: String) : String {
             project.sourceDirectories.forEach {
                 val d = KFiles.joinDir(project.directory, it)
@@ -150,10 +150,10 @@ abstract class JvmCompilerPlugin @Inject constructor(
 
         fun toClassFile(sourceFile: String) = stripSuffix(sourceFile) + ".class"
 
-        val sourceFiles = actionInfo.sourceFiles.map { stripSourceDir(it) }
+        actionInfo.sourceFiles.forEach { sourceFile ->
-        sourceFiles.forEach { sourceFile ->
+            val stripped = stripSourceDir(sourceFile)
-            val classFile = KFiles.joinDir(project.directory, project.classesDir(context), toClassFile(sourceFile))
+            val classFile = File(KFiles.joinDir(project.directory, project.classesDir(context), toClassFile(stripped)))
-            if (classFile == null || File(sourceFile).lastModified() > File(classFile).lastModified()) {
+            if (! classFile.exists() || File(sourceFile).lastModified() > classFile.lastModified()) {
                 return true
             }
         }
@@ -170,7 +170,7 @@ abstract class JvmCompilerPlugin @Inject constructor(
             sourceDirectories.add(sourceDirectory)
         }
         val info = createCompilerActionInfo(project, context, isTest = false)
-        if (isOutOfDate(project, context, info)) {
+        if (isOutdated(project, context, info)) {
             val compiler = ActorUtils.selectAffinityActor(project, context, context.pluginInfo.compilerContributors)
             if (compiler != null) {
                 return compiler.compile(project, context, info)

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/misc/JarUtils.kt

@@ -34,7 +34,8 @@ public class JarUtils {
 
         public fun addSingleFile(directory: String, file: IncludedFile, outputStream: ZipOutputStream,
                 expandJarFiles: Boolean, onError: (Exception) -> Unit = DEFAULT_HANDLER) {
-            file.allFromFiles(directory).forEach { source ->
+            val allFiles = file.allFromFiles(directory)
+            allFiles.forEach { source ->
                 val path = source.path
                 if (source.isDirectory) {
                     log(2, "Writing contents of directory $source")
@@ -68,8 +69,8 @@ public class JarUtils {
                     } else {
                         val entry = JarEntry((file.to + source.path).replace("\\", "/"))
                         entry.time = source.lastModified()
-                        val fromPath = (file.from + "/" + source.path).replace("\\", "/")
+                        val fromPath = source.path.replace("\\", "/")
-                        val entryFile = File(directory, fromPath)
+                        val entryFile = source
                         if (! entryFile.exists()) {
                             throw AssertionError("File should exist: $entryFile")
                         }
@@ -155,9 +156,9 @@ class IncludedFile(val fromOriginal: From, val toOriginal: To, val specs: List<I
     fun allFromFiles(directory: String): List<File> {
         val result = arrayListOf<File>()
         specs.forEach { spec ->
-            val path = spec.toString()
+            val fullDir = KFiles.joinDir(directory, from)
-            spec.toFiles(directory + "/" + from).forEach { source ->
+            spec.toFiles(fullDir).forEach { source ->
-                result.add(source)
+                result.add(if (source.isAbsolute) source else File(fullDir, source.path))
             }
         }
         return result

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/misc/KFiles.kt

@@ -7,6 +7,7 @@ import com.beust.kobalt.api.Kobalt
 import com.beust.kobalt.api.Project
 import com.beust.kobalt.homeDir
 import com.beust.kobalt.internal.build.BuildFile
+import com.beust.kobalt.maven.Md5
 import java.io.File
 import java.io.IOException
 import java.nio.file.*
@@ -160,7 +161,7 @@ class KFiles {
             // Until then, wipe everything first
             if (deleteFirst) to.deleteRecursively()
 //            to.mkdirs()
-            hackCopyRecursively(from, to, replaceExisting, onError)
+            hackCopyRecursively(from, to, replaceExisting = replaceExisting, onError = onError)
         }
 
         /** Private exception class, used to terminate recursive copying */
@@ -171,6 +172,7 @@ class KFiles {
          */
         private fun hackCopyRecursively(from: File, dst: File,
                 replaceExisting: Boolean,
+                checkTimestamp: Boolean = false,
                 onError: (File, IOException) -> OnErrorAction =
                 { file, exception -> throw exception }
         ): Boolean {
@@ -196,9 +198,13 @@ class KFiles {
                         } else if (src.isDirectory) {
                             dstFile.mkdirs()
                         } else {
-                            if (src.copyTo(dstFile, true) != src.length()) {
+                            if (dstFile.exists() && Md5.toMd5(src) == Md5.toMd5(dstFile)) {
-                                if (onError(src, IOException("src.length() != dst.length()")) == OnErrorAction.TERMINATE)
+                                log(2, "  Identical files, not copying $src to $dstFile")
-                                    return false
+                            } else {
+                                if (src.copyTo(dstFile, true) != src.length()) {
+                                    if (onError(src, IOException("src.length() != dst.length()")) == OnErrorAction.TERMINATE)
+                                        return false
+                                }
                             }
                         }
                     }
@@ -242,8 +248,14 @@ class KFiles {
                 log(2, "Windows detected, not overwriting $to")
             } else {
                 try {
-                    log(2, "Copy from $from to ${to!!}")
+                    if (from != null && to != null) {
-                    Files.copy(from, to, option)
+                        if (!Files.exists(to) || Md5.toMd5(from.toFile()) != Md5.toMd5(to.toFile())) {
+                            log(2, "Copy from $from to ${to}")
+                            Files.copy(from, to, option)
+                        } else {
+                            log(2, "  Not copying, indentical files: $from $to")
+                        }
+                    }
                 } catch(ex: IOException) {
                     // Windows is anal about this
                     log(1, "Couldn't copy $from to $to: ${ex.message}")

src/main/kotlin/com/beust/kobalt/plugin/packaging/PackagingPlugin.kt

@@ -17,6 +17,7 @@ import java.io.File
 import java.io.FileOutputStream
 import java.io.OutputStream
 import java.nio.file.Paths
+import java.util.*
 import java.util.jar.JarOutputStream
 import java.util.zip.ZipOutputStream
 import javax.inject.Inject
@@ -236,19 +237,42 @@ class PackagingPlugin @Inject constructor(val dependencyManager : DependencyMana
         val fullArchiveName = context.variant.archiveName(project, archiveName, suffix)
         val archiveDir = File(libsDir(project))
         val result = File(archiveDir.path, fullArchiveName)
-        val outStream = outputStreamFactory(FileOutputStream(result))
         log(2, "Creating $result")
-        JarUtils.addFiles(project.directory, includedFiles, outStream, expandJarFiles)
+        if (isOutdated(project.directory, includedFiles, result)) {
-        log(2, text = "Added ${includedFiles.size} files to $result")
+            val outStream = outputStreamFactory(FileOutputStream(result))
-        outStream.flush()
+            JarUtils.addFiles(project.directory, includedFiles, outStream, expandJarFiles)
-        outStream.close()
+            log(2, text = "Added ${includedFiles.size} files to $result")
-        log(1, "  Created $result")
+            outStream.flush()
+            outStream.close()
+            log(1, "  Created $result")
+        } else {
+            log(2, "  $result is up to date")
+        }
 
         project.projectProperties.put(JAR_NAME, result.absolutePath)
 
         return result
     }
 
+    private fun isOutdated(directory: String, includedFiles: List<IncludedFile>, output: File): Boolean {
+        if (! output.exists()) return true
+
+        val lastModified = output.lastModified()
+        includedFiles.forEach { root ->
+            val allFiles = root.allFromFiles(directory)
+            allFiles.forEach { file ->
+                if (file.isFile) {
+                    if (file.lastModified() > lastModified) {
+                        log(2, "  Outdated $file and $output "
+                                + Date(file.lastModified()) + " " + Date(output.lastModified()))
+                        return true
+                    }
+                }
+            }
+        }
+        return false
+    }
+
     fun addPackage(p: PackageConfig) {
         packages.add(p)
     }

src/test/kotlin/com/beust/kobalt/misc/JarUtilsTest.kt

@@ -0,0 +1,18 @@
+package com.beust.kobalt.misc
+
+import com.beust.kobalt.IFileSpec
+import org.testng.Assert
+import org.testng.annotations.Test
+import javax.inject.Inject
+
+@Test
+class JarUtilsTest @Inject constructor() {
+
+    fun allFromFiles() {
+        val inf = IncludedFile(From("kobaltBuild/classes"), To(""),
+                listOf(IFileSpec.FileSpec("com/beust/kobalt/wrapper/Main.class")))
+        val files = inf.allFromFiles("modules/wrapper")
+        println("Files: $files")
+        Assert.assertEquals(files[0].path, "modules/wrapper/kobaltBuild/classes/com/beust/kobalt/wrapper/Main.class")
+    }
+}