From d9ae38eca11ecfff4e0b197103571fd9743e9b9e Mon Sep 17 00:00:00 2001
From: Cedric Beust <cedric@beust.com>
Date: Thu, 31 Dec 2015 10:18:39 -0800
Subject: [PATCH] outputChecksum needs to be a closure.

---
 .../main/kotlin/com/beust/kobalt/IncrementalTaskInfo.kt    | 7 +++++--
 .../kotlin/com/beust/kobalt/internal/IncrementalManager.kt | 6 ++++--
 .../kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt  | 5 +++--
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/IncrementalTaskInfo.kt b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/IncrementalTaskInfo.kt
index 3fc06a0c..ba3b549b 100644
--- a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/IncrementalTaskInfo.kt
+++ b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/IncrementalTaskInfo.kt
@@ -7,7 +7,10 @@ import com.beust.kobalt.api.Project
  *  if they differ, the task gets run. If they are equal, outputChecksums are then compared.
  * @param outputChecksum The checksum for the output of this task. If null, the output is absent
  * and the task will be run. If non null, it gets compared against the checksum of the previous run and
- * if they differ, the task gets run.
+ * if they differ, the task gets run. Note that this parameter is a closure and not a direct value
+ * because Kobalt needs to call it twice: once before the task and once after a successful execution (to store it).
  * @param task The task to run.
  */
-class IncrementalTaskInfo(val inputChecksum: String?, val outputChecksum: String?, val task: (Project) -> TaskResult)
+class IncrementalTaskInfo(val inputChecksum: String?,
+        val outputChecksum: () -> String?,
+        val task: (Project) -> TaskResult)
diff --git a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/IncrementalManager.kt b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/IncrementalManager.kt
index 42fbedf5..77abda70 100644
--- a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/IncrementalManager.kt
+++ b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/IncrementalManager.kt
@@ -82,10 +82,12 @@ class IncrementalManager(val fileName: String = IncrementalManager.BUILD_INFO_FI
             // TODO: compare the checksums with the previous run
             val taskName = project.name + ":" + taskName
             var upToDate = false
+            var taskOutputChecksum : String? = null
             inputChecksumFor(taskName)?.let { inputChecksum ->
                 if (inputChecksum == iit.inputChecksum) {
                     outputChecksumFor(taskName)?.let { outputChecksum ->
-                        if (outputChecksum == iit.outputChecksum) {
+                        taskOutputChecksum = iit.outputChecksum()
+                        if (outputChecksum == taskOutputChecksum) {
                             upToDate = true
                         } else {
                             logIncremental(1, "Incremental task $taskName output is out of date, running it")
@@ -105,7 +107,7 @@ class IncrementalManager(val fileName: String = IncrementalManager.BUILD_INFO_FI
                         saveInputChecksum(taskName, it)
                         logIncremental(1, "          input checksum \"$it\" saved")
                     }
-                    iit.outputChecksum?.let {
+                    taskOutputChecksum?.let {
                         saveOutputChecksum(taskName, it)
                         logIncremental(1, "          output checksum \"$it\" saved")
                     }
diff --git a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt
index e325e529..42c7ca20 100644
--- a/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt
+++ b/modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt
@@ -172,10 +172,11 @@ abstract class JvmCompilerPlugin @Inject constructor(
         val inputChecksum = Md5.toMd5Directories(project.sourceDirectories.map {
             File(project.directory, it)
         })
-        val outputChecksum = Md5.toMd5Directories(listOf(File(project.classesDir(context))))
         return IncrementalTaskInfo(
                 inputChecksum = inputChecksum,
-                outputChecksum = outputChecksum,
+                outputChecksum = {
+                    Md5.toMd5Directories(listOf(File(project.classesDir(context))))
+                },
                 task = { project -> doTaskCompile(project) }
         )
     }