Make dexMethodCount task incremental unless teamcity output is required

Declare details file as output, circumvent task up-to-date check if teamcity statistics output is required.

buildSrc/src/main/kotlin/plugins/DexMethodCount.kt

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2017 JetBrains s.r.o.
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
- *
+ * that can be found in the license/LICENSE.txt file.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
  */
 
 import com.jakewharton.dex.*
@@ -30,6 +19,10 @@ open class DexMethodCount : DefaultTask() {
         val byClass: Map<String, Int>
     )
 
+    init {
+        outputs.upToDateWhen { !shouldPrintTeamCityStatistics } // always execute when teamCityStatistics output is required
+    }
+
     @InputFile
     lateinit var jarFile: File
 
@@ -42,6 +35,9 @@ open class DexMethodCount : DefaultTask() {
     @Optional
     var teamCityStatistics: Boolean? = null
 
+    private val shouldPrintTeamCityStatistics = teamCityStatistics ?: project.hasProperty("teamcity")
+
+
     @Input
     @Optional
     var artifactName: String? = null
@@ -54,8 +50,12 @@ open class DexMethodCount : DefaultTask() {
         dependsOn(jar)
     }
 
+    @Internal // plain output properties are not supported, mark as internal to suppress warning from validateTaskProperties
     lateinit var counts: Counts
 
+    @get:OutputFile
+    val detailOutputFile: File get() = project.buildDir.resolve("$artifactOrArchiveName-method-count.txt")
+
     @TaskAction
     fun invoke() {
         val methods = dexMethods(jarFile)
@@ -96,7 +96,7 @@ open class DexMethodCount : DefaultTask() {
     }
 
     private fun printTCStats(counts: Counts) {
-        if (teamCityStatistics ?: project.hasProperty("teamcity")) {
+        if (shouldPrintTeamCityStatistics) {
             println("##teamcity[buildStatisticValue key='DexMethodCount_${artifactOrArchiveName}' value='${counts.total}']")
             counts.totalOwnPackages?.let { value ->
                 println("##teamcity[buildStatisticValue key='DexMethodCount_${artifactOrArchiveName}_OwnPackages' value='$value']")
@@ -108,8 +108,7 @@ open class DexMethodCount : DefaultTask() {
     }
 
     private fun outputDetails(counts: Counts) {
-        val detailFile = project.buildDir.resolve("$artifactOrArchiveName-method-count.txt")
+        detailOutputFile.printWriter().use { writer ->
-        detailFile.printWriter().use { writer ->
             writer.println("${counts.total.padRight()}\tTotal methods")
             ownPackages?.let { packages ->
                 writer.println("${counts.totalOwnPackages?.padRight()}\tTotal methods from packages ${packages.joinToString { "$it.*" }}")