Fix symlink issue on windows

src/index.ts

@@ -8,6 +8,7 @@ import { ServerlessOptions, ServerlessInstance, ServerlessFunction } from './typ
 import * as typescript from './typescript'
 
 import { watchFiles } from './watchFiles'
+import { symlink } from './utils'
 
 // Folders
 const serverlessFolder = '.serverless'
@@ -138,12 +139,12 @@ export class TypeScriptPlugin {
   async copyExtras() {
     // include node_modules into build
     if (!fs.existsSync(path.resolve(path.join(buildFolder, 'node_modules')))) {
-      fs.symlinkSync(path.resolve('node_modules'), path.resolve(path.join(buildFolder, 'node_modules')))
+      symlink(path.resolve('node_modules'), path.resolve(path.join(buildFolder, 'node_modules')))
     }
 
     // include package.json into build so Serverless can exlcude devDeps during packaging
     if (!fs.existsSync(path.resolve(path.join(buildFolder, 'package.json')))) {
-      fs.symlinkSync(path.resolve('package.json'), path.resolve(path.join(buildFolder, 'package.json')))
+      symlink(path.resolve('package.json'), path.resolve(path.join(buildFolder, 'package.json')))
     }
 
     // include any "extras" from the "include" section

src/utils/index.ts

@@ -0,0 +1,28 @@
+import * as fs from 'fs-extra'
+
+export interface SymlinkException {
+  code: string
+  errno: number
+}
+
+const isMissingSymlinkPermission = (error: SymlinkException): boolean => {
+  // Generally happens when no admin rights with UAC enabled on Windows.
+  return error.code === 'EPERM' && error.errno === -4048
+}
+
+const copyIfMissingSymlinkPermission =
+  (srcpath: string, dstpath: string, error: SymlinkException) => {
+    if (isMissingSymlinkPermission(error)) {
+      fs.copySync(srcpath, dstpath)
+    } else {
+      throw error
+    }
+  }
+
+export const symlink = (srcpath: string, dstpath: string, type?: string) => {
+  try {
+    fs.symlinkSync(srcpath, dstpath, type)
+  } catch (error) {
+    copyIfMissingSymlinkPermission(srcpath, dstpath, error)
+  }
+}