Automatically use appropriate webpack mode based on run/build

README.md

@@ -108,6 +108,7 @@ kotlinFrontend {
         port = 8088   // dev server port
         proxyUrl = "" | "http://...."  // URL to be proxied, useful to proxy backend webserver
         stats = "errors-only"  // log level
+        mode = "production" | "development" | "none" // used for webpack 4+ built-in optimizations
     }
 }
 ```
@@ -116,6 +117,8 @@ dev server log is located at `build/logs/webpack-dev-server.log`
 
 config file is generated at `build/webpack.config.js`
 
+If mode is not specified, the default behavior is to use development mode for running the dev server, and production mode for creating the final bundle. See [webpack documentation](https://webpack.js.org/concepts/mode/) for more information about modes.
+
 ## webpack configuration customization
 
 To customize webpack configuration, you can apply additional scripts by placing them in the directory `webpack.config.d`. The scripts will be appended to the end of config script. Use number prefix to change order (it is very similar to UNIX rc.d config directories)

kotlin-frontend/src/main/kotlin/org/jetbrains/kotlin/gradle/frontend/npm/NpmModuleVersion.kt

@@ -0,0 +1,27 @@
+package org.jetbrains.kotlin.gradle.frontend.npm
+
+import groovy.json.JsonSlurper
+import org.gradle.api.GradleException
+import org.gradle.api.Project
+import kotlin.reflect.KProperty
+
+class NpmModuleVersion(project: Project, module: String) {
+    @Suppress("UNCHECKED_CAST")
+    val version: String = project.buildDir.resolve("node_modules/$module/package.json")
+            .let { JsonSlurper().parse(it) as Map<String, Any?> }["version"]
+            ?.let { it as String } ?: throw GradleException("Module \"$module\" not found")
+
+    val major: Int by VersionComponent(0)
+
+    val minor: Int by VersionComponent(1)
+
+    val patch: Int by VersionComponent(2)
+
+    private class VersionComponent(val component: Int) {
+        operator fun getValue(thisRef: NpmModuleVersion, property: KProperty<*>): Int {
+            return thisRef.version.split(".")
+                    .getOrNull(component)
+                    ?.toInt() ?: 0
+        }
+    }
+}

kotlin-frontend/src/main/kotlin/org/jetbrains/kotlin/gradle/frontend/webpack/GenerateWebPackConfigTask.kt

@@ -130,7 +130,6 @@ open class GenerateWebPackConfigTask : DefaultTask() {
         val resolveRoots = getModuleResolveRoots(false)
 
         val json = linkedMapOf(
-                "mode" to bundle.mode,
                 "context" to getContextDir(false).absolutePath,
                 "entry" to mapOf(
                         bundle.bundleName to kotlinOutput(project).nameWithoutExtension.let { "./$it" }

kotlin-frontend/src/main/kotlin/org/jetbrains/kotlin/gradle/frontend/webpack/WebPackBundleTask.kt

@@ -1,8 +1,8 @@
 package org.jetbrains.kotlin.gradle.frontend.webpack
 
-import groovy.json.JsonSlurper
 import org.gradle.api.*
 import org.gradle.api.tasks.*
+import org.jetbrains.kotlin.gradle.frontend.npm.NpmModuleVersion
 import org.jetbrains.kotlin.gradle.frontend.util.*
 
 /**
@@ -29,23 +29,15 @@ open class WebPackBundleTask : DefaultTask() {
 
     @TaskAction
     fun buildBundle() {
-        @Suppress("UNCHECKED_CAST")
-        val webpackVersion = project.buildDir.resolve("node_modules/webpack/package.json")
-                .let { JsonSlurper().parse(it) as Map<String, Any?> }["version"]
-                ?.let { it as String }
-
         val processBuilderCommands = arrayListOf(
                 nodePath(project, "node").first().absolutePath,
                 project.buildDir.resolve("node_modules/webpack/bin/webpack.js").absolutePath,
                 "--config", webPackConfigFile.absolutePath
         )
-        val webpackMajorVersion = webpackVersion
-                ?.split('.')
-                ?.firstOrNull()
-                ?.toInt()
-        if (webpackMajorVersion != null && webpackMajorVersion >= 4) {
+
+        if (NpmModuleVersion(project, "webpack").major >= 4) {
             processBuilderCommands.addAll(arrayOf(
-                    "--mode", config.mode
+                    "--mode", config.mode ?: "production"
             ))
         }
         ProcessBuilder(processBuilderCommands)

kotlin-frontend/src/main/kotlin/org/jetbrains/kotlin/gradle/frontend/webpack/WebPackExtension.kt

@@ -41,5 +41,6 @@ open class WebPackExtension(project: Project) : BundleConfig {
     var webpackConfigFile: Any? = null
 
     @Input
-    var mode: String = "development"
+    @Optional
+    var mode: String? = null
 }

kotlin-frontend/src/main/kotlin/org/jetbrains/kotlin/gradle/frontend/webpack/WebPackRunTask.kt

@@ -4,6 +4,7 @@ import groovy.json.*
 import org.codehaus.groovy.runtime.*
 import org.gradle.api.*
 import org.gradle.api.tasks.*
+import org.jetbrains.kotlin.gradle.frontend.npm.NpmModuleVersion
 import org.jetbrains.kotlin.gradle.frontend.servers.*
 import org.jetbrains.kotlin.gradle.frontend.util.*
 import java.io.*
@@ -77,6 +78,9 @@ open class WebPackRunTask : AbstractStartStopTask<WebPackRunTask.State>() {
                         .replace("require('\$RunConfig\$')",
                                 JsonBuilder(GenerateWebpackHelperTask.config(project, config, webPackConfigFile)).toPrettyString()
                         )
+                        .replace("\$SetMode\$\n",
+                                if (NpmModuleVersion(project, "webpack").major >= 4) "config.mode = \"${config.mode ?: "development"}\";\n" else ""
+                        )
         )
 
         try {

kotlin-frontend/src/main/resources/kotlin/webpack/webpack-dev-server-launcher.js

@@ -11,6 +11,7 @@ var devServerVersion = require(__dirname + '/node_modules/webpack-dev-server/pac
 var RunConfig = require('$RunConfig$');
 
 var config = require(RunConfig.webPackConfig);
+$SetMode$
 
 for (var name in config.entry) {
     if (config.entry.hasOwnProperty(name)) {

kotlin-frontend/src/test/kotlin/org/jetbrains/kotlin/gradle/frontend/SimpleFrontendProjectTest.kt

@@ -97,6 +97,7 @@ class SimpleFrontendProjectTest(gradleVersion: String, kotlinVersion: String) :
                 block("webpackBundle") {
                     line("port = $port")
                     line("bundleName = \"main\"")
+                    line("mode = \"development\"")
                 }
             }