Gradle, NPM, windows: creating symlink without administrator privilege

#KT-31694 Fixed

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/npm/NpmSimpleLinker.kt

@@ -5,15 +5,19 @@
 
 package org.jetbrains.kotlin.gradle.targets.js.npm
 
+import com.google.gson.stream.JsonWriter
 import org.gradle.api.Project
 import org.jetbrains.kotlin.gradle.targets.js.nodejs.nodeJs
+import java.io.ByteArrayInputStream
+import java.io.File
+import java.io.StringWriter
 import java.nio.file.Files
 
 /**
  * Handles simple case, when there are no npm depenencies required, but some tasks steel needs
  * node_modules with symlinked packages and packages_imported
  */
-class NpmSimpleLinker(rootProject: Project) {
+class NpmSimpleLinker(val rootProject: Project) {
     private val rootProjectNodeModules = rootProject.nodeJs.root.rootPackageDir.resolve(NpmProject.NODE_MODULES)
 
     fun link(projects: Collection<NpmProjectPackage>) {
@@ -29,19 +33,71 @@ class NpmSimpleLinker(rootProject: Project) {
 
         rootProjectNodeModules.mkdirs()
 
+        val fsLinker = createFSLinker()
+
         // packages
         projects.forEach {
-            Files.createSymbolicLink(getNodeModulePath(it.npmProject.name), it.npmProject.dir.canonicalFile.toPath())
+            fsLinker.link(getNodeModulePath(it.npmProject.name), it.npmProject.dir.canonicalFile)
         }
 
         // packages_imported
         projects.flatMapTo(mutableSetOf()) {
             it.gradleDependencies.externalModules.map { gradleNodeModule -> gradleNodeModule }
         }.forEach {
-            Files.createSymbolicLink(getNodeModulePath(it.name), it.path.canonicalFile.toPath())
+            fsLinker.link(getNodeModulePath(it.name), it.path.canonicalFile)
+        }
+
+        fsLinker.execute()
+    }
+
+    private fun getNodeModulePath(name: String) = rootProjectNodeModules.resolve(name).canonicalFile
+
+    interface FSLinker {
+        fun link(linkFile: File, target: File)
+        fun execute() = Unit
+    }
+
+    fun createFSLinker(): FSLinker =
+        if (rootProject.nodeJs.root.environment.isWindows) WindowsJunctionFsLinker(rootProject, rootProjectNodeModules)
+        else JavaFsLinker()
+
+    class WindowsJunctionFsLinker(val project: Project, val dir: File) : FSLinker {
+        val js = StringBuilder()
+
+        init {
+            js.appendln("var fs = require('fs')")
+        }
+
+        fun addLink(linkFile: String, target: String) {
+            js.appendln("fs.symlinkSync(${jsQuotedString(linkFile)}, ${jsQuotedString(target)}, 'junction')")
+        }
+
+        private fun jsQuotedString(str: String) = StringWriter().also {
+            JsonWriter(it).value(str)
+        }.toString()
+
+        override fun link(linkFile: File, target: File) {
+            addLink(linkFile.absolutePath, target.absolutePath)
+        }
+
+        override fun execute() {
+            val result = project.exec { exec ->
+                exec.workingDir = dir
+                exec.executable = project.nodeJs.root.environment.nodeExecutable
+                exec.standardInput = ByteArrayInputStream(js.toString().toByteArray())
+                exec.standardOutput = System.`out`
+                exec.errorOutput = System.err
+            }
+
+            if (result.exitValue != 0) {
+                error("Cannot create window junctions: nodejs exited with ${result.exitValue}")
+            }
         }
     }
 
-    private fun getNodeModulePath(name: String) =
-        rootProjectNodeModules.resolve(name).canonicalFile.toPath()
+    class JavaFsLinker : FSLinker {
+        override fun link(linkFile: File, target: File) {
+            Files.createSymbolicLink(linkFile.toPath(), target.toPath())
+        }
+    }
 }