Add support for SmallModulesFor style (#894)

Author: lwronski

modules/cli-options/src/main/scala/scala/cli/commands/ScalaJsOptions.scala

@@ -46,9 +46,12 @@ final case class ScalaJsOptions(
   @HelpMessage("Avoid lets and consts when using vars has the same observable semantics.")
     jsAvoidLetsAndConsts: Option[Boolean] = None,
   @Group("Scala.js")
-  @HelpMessage("The Scala.js module split style: fewestmodules, smallestmodules")
+  @HelpMessage("The Scala.js module split style: fewestmodules, smallestmodules, smallmodulesfor")
     jsModuleSplitStyle: Option[String] = None,
   @Group("Scala.js")
+  @HelpMessage("Create as many small modules as possible for the classes in the passed packages and their subpackages.")
+    jsSmallModuleForPackage: List[String] = Nil,
+  @Group("Scala.js")
   @HelpMessage("The Scala.js ECMA Script version: es5_1, es2015, es2016, es2017, es2018, es2019, es2020, es2021")
     jsEsVersion: Option[String] = None,
 

modules/cli/src/main/scala/scala/cli/commands/util/SharedOptionsUtil.scala

@@ -43,6 +43,7 @@ object SharedOptionsUtil {
         avoidClasses = jsAvoidClasses,
         avoidLetsAndConsts = jsAvoidLetsAndConsts,
         moduleSplitStyleStr = jsModuleSplitStyle,
+        smallModuleForPackage = jsSmallModuleForPackage,
         esVersionStr = jsEsVersion
       )
     }

modules/directives/src/main/scala/scala/build/preprocessing/directives/UsingScalaJsOptionsDirectiveHandler.scala

@@ -20,6 +20,8 @@ case object UsingScalaJsOptionsDirectiveHandler extends UsingDirectiveHandler {
       |
       |`//> using jsModuleKind` _value_
       |
+      |`//> using jsSmallModuleForPackage` _value1_, _value2_
+      |
       |`//> using jsCheckIr` _true|false_
       |
       |`//> using jsEmitSourceMaps` _true|false_
@@ -50,6 +52,7 @@ case object UsingScalaJsOptionsDirectiveHandler extends UsingDirectiveHandler {
       "jsModuleKind",
       "jsCheckIr",
       "jsEmitSourceMaps",
+      "jsSmallModuleForPackage",
       "jsDom",
       "jsHeader",
       "jsAllowBigIntsForLongs",
@@ -71,7 +74,7 @@ case object UsingScalaJsOptionsDirectiveHandler extends UsingDirectiveHandler {
     groupedValues.scopedStringValues.headOption.map(_.positioned.value)
 
   override def getSupportedTypes(key: String) = key match {
-    case "jsVersion" | "jsHeader" | "jsModuleKind" | "jsMode" | "jsModuleSplitStyleStr" | "jsEsVersionStr" =>
+    case "jsVersion" | "jsHeader" | "jsModuleKind" | "jsMode" | "jsModuleSplitStyleStr" | "jsEsVersionStr" | "jsSmallModuleForPackage" =>
       Set(UsingDirectiveValueKind.STRING)
     case "jsCheckIr" | "jsAllowBigIntsForLongs" | "jsEmitSourceMaps" | "jsDom" | "jsAvoidClasses" | "jsAvoidLetsAndConsts" =>
       Set(UsingDirectiveValueKind.BOOLEAN, UsingDirectiveValueKind.EMPTY)
@@ -82,6 +85,8 @@ case object UsingScalaJsOptionsDirectiveHandler extends UsingDirectiveHandler {
       UsingDirectiveValueNumberBounds(1, 1)
     case "jsCheckIr" | "jsAllowBigIntsForLongs" | "jsEmitSourceMaps" | "jsDom" | "jsAvoidClasses" | "jsAvoidLetsAndConsts" =>
       UsingDirectiveValueNumberBounds(0, 1)
+    case "jsSmallModuleForPackage" =>
+      UsingDirectiveValueNumberBounds(1)
   }
 
   def handleValues(
@@ -102,6 +107,11 @@ case object UsingScalaJsOptionsDirectiveHandler extends UsingDirectiveHandler {
         case "jsEmitSourceMaps" => BuildOptions(scalaJsOptions =
             ScalaJsOptions(emitSourceMaps = getBooleanValue(groupedValues))
           )
+        case "jsSmallModuleForPackage" => BuildOptions(scalaJsOptions =
+            ScalaJsOptions(smallModuleForPackage =
+              groupedValues.scopedStringValues.map(_.positioned.value).toList
+            )
+          )
         case "jsDom" =>
           BuildOptions(scalaJsOptions = ScalaJsOptions(dom = getBooleanOption(groupedValues)))
         case "jsHeader" =>

modules/integration/src/test/scala/scala/cli/integration/PackageTestDefinitions.scala

@@ -271,6 +271,49 @@ abstract class PackageTestDefinitions(val scalaVersionOpt: Option[String])
       expect(output == message)
     }
   }
+  def smallModulesJsTest(): Unit = {
+    val fileName = "Hello.scala"
+    val message  = "Hello World from JS"
+    val inputs = TestInputs(
+      Seq(
+        os.rel / fileName ->
+          s"""|//> using jsModuleKind "es"
+              |//> using jsModuleSplitStyleStr "smallmodulesfor"
+              |//> using jsSmallModuleForPackage "test"
+              |
+              |package test
+              |
+              |case class Foo(bar: String)
+              |
+              |object Hello extends App {
+              |  println(Foo("$message").bar)
+              |}
+              |""".stripMargin
+      )
+    )
+    val destDir = fileName.stripSuffix(".scala")
+    inputs.fromRoot { root =>
+      os.proc(
+        TestUtil.cli,
+        "package",
+        extraOptions,
+        fileName,
+        "--js",
+        "-o",
+        destDir
+      ).call(
+        cwd = root,
+        stdin = os.Inherit,
+        stdout = os.Inherit
+      )
+
+      val launcher = root / destDir / "main.js"
+      val nodePath = TestUtil.fromPath("node").getOrElse("node")
+      os.write(root / "package.json", "{\n\n  \"type\": \"module\"\n\n}") // enable es module
+      val output = os.proc(nodePath, launcher.toString).call(cwd = root).out.text().trim
+      expect(output == message)
+    }
+  }
 
   def jsHeaderTest(): Unit = {
     val fileName        = "Hello.scala"
@@ -312,6 +355,9 @@ abstract class PackageTestDefinitions(val scalaVersionOpt: Option[String])
     test("multi modules js") {
       multiModulesJsTest()
     }
+    test("small modules js") {
+      smallModulesJsTest()
+    }
     test("js header in release mode") {
       jsHeaderTest()
     }

modules/options/src/main/scala/scala/build/internal/ScalaJsLinkerConfig.scala

@@ -6,6 +6,7 @@ final case class ScalaJsLinkerConfig(
   checkIR: Boolean = false,
   sourceMap: Boolean = true,
   moduleSplitStyle: String = ScalaJsLinkerConfig.ModuleSplitStyle.FewestModules,
+  smallModuleForPackage: List[String] = Nil,
   esFeatures: ScalaJsLinkerConfig.ESFeatures = ScalaJsLinkerConfig.ESFeatures(),
   jsHeader: Option[String] = None,
   prettyPrint: Boolean = false,
@@ -24,6 +25,11 @@ final case class ScalaJsLinkerConfig(
         Nil
     val moduleKindArgs       = Seq("--moduleKind", moduleKind)
     val moduleSplitStyleArgs = Seq("--moduleSplitStyle", moduleSplitStyle)
+    val smallModuleForPackageArgs =
+      if (smallModuleForPackage.nonEmpty)
+        Seq("--smallModuleForPackages", smallModuleForPackage.mkString(","))
+      else
+        Nil
     val esFeaturesArgs =
       if (esFeatures.esVersion == ScalaJsLinkerConfig.ESVersion.ES2015)
         Seq("--es2015")
@@ -42,6 +48,7 @@ final case class ScalaJsLinkerConfig(
       semanticsArgs,
       moduleKindArgs,
       moduleSplitStyleArgs,
+      smallModuleForPackageArgs,
       esFeaturesArgs,
       checkIRArgs,
       sourceMapArgs,
@@ -64,6 +71,7 @@ object ScalaJsLinkerConfig {
   object ModuleSplitStyle {
     val FewestModules   = "FewestModules"
     val SmallestModules = "SmallestModules"
+    val SmallModulesFor = "SmallModulesFor"
   }
 
   final case class ESFeatures(

modules/options/src/main/scala/scala/build/options/ScalaJsOptions.scala

@@ -21,6 +21,7 @@ final case class ScalaJsOptions(
   avoidClasses: Option[Boolean] = None,
   avoidLetsAndConsts: Option[Boolean] = None,
   moduleSplitStyleStr: Option[String] = None,
+  smallModuleForPackage: List[String] = Nil,
   esVersionStr: Option[String] = None,
   noOpt: Option[Boolean] = None
 ) {
@@ -59,6 +60,7 @@ final case class ScalaJsOptions(
       .map {
         case "fewestmodules"   => ScalaJsLinkerConfig.ModuleSplitStyle.FewestModules
         case "smallestmodules" => ScalaJsLinkerConfig.ModuleSplitStyle.SmallestModules
+        case "smallmodulesfor" => ScalaJsLinkerConfig.ModuleSplitStyle.SmallModulesFor
         case unknown =>
           logger.message(
             s"Warning: unrecognized argument: $unknown for --js-module-split-style parameter, use default value: fewestmodules"
@@ -130,6 +132,7 @@ final case class ScalaJsOptions(
       checkIr.getOrElse(false), // meh
       emitSourceMaps,
       moduleSplitStyle(logger),
+      smallModuleForPackage,
       esFeatures,
       header
     )

project/deps.sc

@@ -44,7 +44,7 @@ object InternalDeps {
   object Versions {
     def mill          = os.read(os.pwd / ".mill-version").trim
     def lefouMillwRef = "166bcdf5741de8569e0630e18c3b2ef7e252cd96"
-    def scalaJsCli    = "1.1.1-sc3.1"
+    def scalaJsCli    = "1.1.1-sc4.1"
   }
 }
 

website/docs/guides/scala-js.md

@@ -52,7 +52,9 @@ node hello.js
 Hello World from Scala.js
 -->
 
-### Module Split Style - Smallest Modules
+### Module Split Style 
+
+### Smallest Modules
 
 Passing `--js-module-split-style smallestmodules` to the `package` sub-command creates js modules that are as small as possible.
 Scala.js linker generates a lot of js modules, which are copied to the `output` directory.
@@ -78,6 +80,26 @@ node hello/main.js
 Hello World from Scala.js
 -->
 
+### Small Modules For
+
+Passing `--js-module-split-style smallestmodules` to the `package` sub-command creates many small modules as possibles for the classes in the listed packages (and their subpackages). To define packages use `jsSmallModuleForPackage` parameter.
+
+```scala title=SmallestModules.scala
+//> using jsModuleKind "es"
+//> using jsModuleSplitStyleStr "smallmodulesfor"
+//> using jsSmallModuleForPackage "com.example.test", "com.example.example""
+
+package com.example.test
+
+import scala.scalajs.js
+
+case class Foo(txt: String)
+
+object Hello extends App {
+  println(Foo("Hello World from Scala.js").txt)
+}
+```
+
 ## Emit source maps
 
 Passing `--js-emit-source-maps` to the `package` sub-command emits source maps alongside js files. To set the destination path of source maps, pass `--js-source-maps-path` flag with the argument.

website/docs/reference/cli-options.md

@@ -1095,7 +1095,11 @@ Avoid lets and consts when using vars has the same observable semantics.
 
 #### `--js-module-split-style`
 
-The Scala.js module split style: fewestmodules, smallestmodules
+The Scala.js module split style: fewestmodules, smallestmodules, smallmodulesfor
+
+#### `--js-small-module-for-package`
+
+Create as many small modules as possible for the classes in the passed packages and their subpackages.
 
 #### `--js-es-version`
 

website/docs/reference/directives.md

@@ -192,6 +192,8 @@ Add Scala.js options
 
 `//> using jsModuleKind` _value_
 
+`//> using jsSmallModuleForPackage` _value1_, _value2_
+
 `//> using jsCheckIr` _true|false_
 
 `//> using jsEmitSourceMaps` _true|false_