wip

scala-js · gzm0 · Mar 10, 2024 · Mar 10, 2024 · Mar 10, 2024 · Mar 3, 2024
commit 639d93b45097927ccf1db369c5534f3e49873477
diff --git a/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala b/linker/jvm/src/main/scala/org/scalajs/linker/backend/closure/ClosureLinkerBackend.scala
@@ -218,15 +218,15 @@ final class ClosureLinkerBackend(config: LinkerBackendImpl.Config)
 
       protected def moduleChanged(moduleID: ModuleID): Boolean = true // no incremental support
 
-      protected def writeModuleWithoutSourceMap(moduleID: ModuleID): ByteBuffer = {
+      protected def writeModuleWithoutSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): ByteBuffer = {
         val jsFileWriter = new ByteArrayOutputStream()
         val jsFileStrWriter = new java.io.OutputStreamWriter(jsFileWriter, StandardCharsets.UTF_8)
         writeCode(jsFileStrWriter)
         jsFileStrWriter.flush()
         ByteBuffer.wrap(jsFileWriter.toByteArray())
       }
 
-      protected def writeModuleWithSourceMap(moduleID: ModuleID): (ByteBuffer, ByteBuffer) = {
+      protected def writeModuleWithSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): (ByteBuffer, ByteBuffer) = {
         val jsFileURI = OutputPatternsImpl.jsFileURI(config.outputPatterns, moduleID.id)
         val sourceMapURI = OutputPatternsImpl.sourceMapURI(config.outputPatterns, moduleID.id)
 

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/BasicLinkerBackend.scala
@@ -93,7 +93,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
       protected def moduleChanged(moduleID: ModuleID): Boolean =
         allChanged || emitterResult.body(moduleID)._2
 
-      protected def writeModuleWithoutSourceMap(moduleID: ModuleID): ByteBuffer = {
+      protected def writeModuleWithoutSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): ByteBuffer = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
         val (trees, _) = emitterResult.body(moduleID)
 
@@ -104,7 +104,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
         jsFileWriter.write(printedModuleSetCache.headerBytes)
         jsFileWriter.writeASCIIString("'use strict';\n")
 
-        val printer = new Printers.JSTreePrinter(jsFileWriter)
+        val printer = new Printers.JSTreePrinter(prevFile, jsFileWriter)
         for (tree <- trees)
           printer.printStat(tree)
 
@@ -114,7 +114,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
         jsFileWriter.toByteBuffer()
       }
 
-      protected def writeModuleWithSourceMap(moduleID: ModuleID): (ByteBuffer, ByteBuffer) = {
+      protected def writeModuleWithSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): (ByteBuffer, ByteBuffer) = {
         val cache = printedModuleSetCache.getModuleCache(moduleID)
         val (trees, _) = emitterResult.body(moduleID)
 
@@ -136,7 +136,7 @@ final class BasicLinkerBackend(config: LinkerBackendImpl.Config)
         jsFileWriter.writeASCIIString("'use strict';\n")
         smWriter.nextLine()
 
-        val printer = new Printers.JSTreePrinterWithSourceMap(jsFileWriter, smWriter, initIndent = 0)
+        val printer = new Printers.JSTreePrinterWithSourceMap(prevFile, jsFileWriter, smWriter, initIndent = 0)
         for (tree <- trees)
           printer.printStat(tree)
 
@@ -245,7 +245,7 @@ private object BasicLinkerBackend {
         Nil // Fast path
       } else {
         val jsCodeWriter = new ByteArrayWriter()
-        val printer = new Printers.JSTreePrinter(jsCodeWriter, indent)
+        val printer = new Printers.JSTreePrinter(None, jsCodeWriter, indent)
 
         trees.foreach(printer.printStat(_))
 
@@ -261,7 +261,7 @@ private object BasicLinkerBackend {
       } else {
         val jsCodeWriter = new ByteArrayWriter()
         val smFragmentBuilder = new SourceMapWriter.FragmentBuilder()
-        val printer = new Printers.JSTreePrinterWithSourceMap(jsCodeWriter, smFragmentBuilder, indent)
+        val printer = new Printers.JSTreePrinterWithSourceMap(None, jsCodeWriter, smFragmentBuilder, indent)
 
         trees.foreach(printer.printStat(_))
         smFragmentBuilder.complete()

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/OutputWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/OutputWriter.scala
@@ -32,9 +32,9 @@ private[backend] abstract class OutputWriter(output: OutputDirectory,
 
   protected def moduleChanged(moduleID: ModuleID): Boolean
 
-  protected def writeModuleWithoutSourceMap(moduleID: ModuleID): ByteBuffer
+  protected def writeModuleWithoutSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): ByteBuffer
 
-  protected def writeModuleWithSourceMap(moduleID: ModuleID): (ByteBuffer, ByteBuffer)
+  protected def writeModuleWithSourceMap(moduleID: ModuleID, prevFile: Option[ByteBuffer]): (ByteBuffer, ByteBuffer)
 
   def write(moduleSet: ModuleSet)(implicit ec: ExecutionContext): Future[Report] = {
     val ioThrottler = new IOThrottler(config.maxConcurrentWrites)
@@ -67,13 +67,20 @@ private[backend] abstract class OutputWriter(output: OutputDirectory,
       implicit ec: ExecutionContext): Future[Report.Module] = {
     val jsFileName = OutputPatternsImpl.jsFile(config.outputPatterns, moduleID.id)
 
+    val prevFileFuture =
+      if (existingFiles.contains(jsFileName)) outputImpl.readFull(jsFileName).map(Some(_))
+      else Future.successful(None)
+
     if (config.sourceMap) {
       val sourceMapFileName = OutputPatternsImpl.sourceMapFile(config.outputPatterns, moduleID.id)
       val report = new ReportImpl.ModuleImpl(moduleID.id, jsFileName, Some(sourceMapFileName), moduleKind)
 
       if (moduleChanged(moduleID)) {
-        val (code, sourceMap) = writeModuleWithSourceMap(moduleID)
         for {
+          prevFile <- prevFileFuture
+          (code, sourceMap) = writeModuleWithSourceMap(moduleID, prevFile)
+
+          // TODO: We should not read the file again, but use the existing buffer to compare if a write is required.
           _ <- outputImpl.writeFull(jsFileName, code, skipContentCheck)
           _ <- outputImpl.writeFull(sourceMapFileName, sourceMap, skipContentCheck)
         } yield {
@@ -86,8 +93,9 @@ private[backend] abstract class OutputWriter(output: OutputDirectory,
       val report = new ReportImpl.ModuleImpl(moduleID.id, jsFileName, None, moduleKind)
 
       if (moduleChanged(moduleID)) {
-        val code = writeModuleWithoutSourceMap(moduleID)
         for {
+          prevFile <- prevFileFuture
+          code = writeModuleWithoutSourceMap(moduleID, prevFile)
           _ <- outputImpl.writeFull(jsFileName, code, skipContentCheck)
         } yield {
           report

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/ByteArrayWriter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/ByteArrayWriter.scala
@@ -44,6 +44,14 @@ private[backend] final class ByteArrayWriter(originalCapacity: Int) extends Outp
     size += 1
   }
 
+  def write(bs: ByteBuffer): Unit = {
+    val len = bs.remaining()
+    val newSize = size + len
+    ensureCapacity(newSize)
+    bs.get(buffer, size, len)
+    size = newSize
+  }
+
   override def write(bs: Array[Byte]): Unit =
     write(bs, 0, bs.length)
 

diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Printers.scala
@@ -12,6 +12,7 @@
 
 package org.scalajs.linker.backend.javascript
 
+import java.nio.ByteBuffer
 import java.nio.charset.StandardCharsets
 
 import scala.annotation.switch
@@ -33,7 +34,7 @@ import Trees._
 object Printers {
   private val ReusableIndentArray = Array.fill(128)(' '.toByte)
 
-  class JSTreePrinter(protected val out: ByteArrayWriter, initIndent: Int = 0) {
+  class JSTreePrinter(prevFile: Option[ByteBuffer], protected val out: ByteArrayWriter, initIndent: Int = 0) {
     private final val IndentStep = 2
 
     private var indentMargin = initIndent * IndentStep
@@ -762,8 +763,12 @@ object Printers {
         print("]")
     }
 
-    protected def print(printedTree: PrintedTree): Unit =
-      out.write(printedTree.jsCode)
+    protected def print(printedTree: PrintedTree): Unit = {
+      val startPos = out.currentSize
+      out.write(printedTree.jsCode(prevFile))
+      val endPos = out.currentSize
+      printedTree.written(startPos, endPos)
+    }
 
     private def print(exportName: ExportName): Unit =
       printEscapeJS(exportName.name)
@@ -776,9 +781,9 @@ object Printers {
       out.write(c)
   }
 
-  class JSTreePrinterWithSourceMap(_out: ByteArrayWriter,
+  class JSTreePrinterWithSourceMap(prevFile: Option[ByteBuffer], _out: ByteArrayWriter,
       sourceMap: SourceMapWriter.Builder, initIndent: Int)
-      extends JSTreePrinter(_out, initIndent) {
+      extends JSTreePrinter(prevFile, _out, initIndent) {
 
     private var column = 0
 
@@ -853,7 +858,7 @@ object Printers {
 
   /** A printer that shows `Tree`s for debugging, not for pretty-printing. */
   private class JSTreeShowPrinter(_out: ByteArrayWriter, initIndent: Int = 0)
-      extends JSTreePrinter(_out, initIndent) {
+      extends JSTreePrinter(None, _out, initIndent) {
     def printTreeForShow(tree: Tree): Unit =
       printTree(tree, isStat = true)
 
@@ -862,5 +867,9 @@ object Printers {
       print(ident.resolver.debugString)
       print(">")
     }
+
+    override protected def print(printedTree: PrintedTree): Unit = {
+      print(printedTree.show)
+    }
   }
 }
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/javascript/Trees.scala
@@ -13,8 +13,10 @@
 package org.scalajs.linker.backend.javascript
 
 import scala.annotation.switch
+import scala.concurrent.Future
 
 import java.nio.charset.StandardCharsets
+import java.nio.ByteBuffer
 
 import org.scalajs.ir
 import org.scalajs.ir.{OriginalName, Position}
@@ -548,14 +550,42 @@ object Trees {
    *  A cleaner abstraction would be to have something like ir.Tree.Transient
    *  (for different output formats), but for now, we do not need this.
    */
-  sealed case class PrintedTree(jsCode: Array[Byte],
-      sourceMapFragment: SourceMapWriter.Fragment) extends Tree {
+  sealed class PrintedTree private (
+    private[this] var state: PrintedTree.State,
+    val sourceMapFragment: SourceMapWriter.Fragment
+  ) extends Tree {
     val pos: Position = Position.NoPosition
 
-    override def show: String = new String(jsCode, StandardCharsets.UTF_8)
+    override def show: String = state match {
+      case PrintedTree.InMemory(jsCode) =>
+        new String(jsCode, StandardCharsets.UTF_8)
+
+      case PrintedTree.OnDisk(startPos, endPos) =>
+        f"<printed (on disk @ $startPos-$endPos)>"
+    }
+
+    def jsCode(prevFile: Option[ByteBuffer]): ByteBuffer = state match {
+      case PrintedTree.InMemory(jsCode) =>
+        ByteBuffer.wrap(jsCode).asReadOnlyBuffer()
+
+      case PrintedTree.OnDisk(startPos, endPos) =>
+        prevFile.get.slice().position(startPos).limit(endPos)
+    }
+
+    def written(startPos: Int, endPos: Int): Unit =
+      this.state = PrintedTree.OnDisk(startPos, endPos)
   }
 
   object PrintedTree {
     def empty: PrintedTree = PrintedTree(Array(), SourceMapWriter.Fragment.Empty)
+
+    def apply(jsCode: Array[Byte],
+        sourceMapFragment: SourceMapWriter.Fragment): PrintedTree = {
+      new PrintedTree(InMemory(jsCode), sourceMapFragment)
+    }
+
+    sealed trait State
+    final case class InMemory(jsCode: Array[Byte]) extends State
+    final case class OnDisk(startPos: Int, endPos: Int) extends State
   }
 }
diff --git a/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala b/linker/shared/src/test/scala/org/scalajs/linker/backend/javascript/PrintersTest.scala
@@ -32,7 +32,7 @@ class PrintersTest {
 
   private def printTree(tree: Tree): String = {
     val out = new ByteArrayWriter
-    val printer = new Printers.JSTreePrinter(out)
+    val printer = new Printers.JSTreePrinter(None, out)
     printer.printStat(tree)
     new String(out.toByteArray(), UTF_8)
   }
@@ -224,6 +224,13 @@ class PrintersTest {
     assertEquals("test", tree.show)
   }
 
+  @Test def showWrittenPrintedTree(): Unit = {
+    val tree = PrintedTree("test".getBytes(UTF_8), SourceMapWriter.Fragment.Empty)
+    tree.written(100, 2000)
+
+    assertEquals("<printed (on disk @ 100-2000)>", tree.show)
+  }
+
   @Test def showNestedPrintedTree(): Unit = {
     val tree = PrintedTree("  test\n".getBytes(UTF_8), SourceMapWriter.Fragment.Empty)