fix(pencil): Copy on failed symlink for Windows

Closes #89, #23, #103, #24.

src/index.ts

@@ -136,14 +136,17 @@ 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')), 'junction')
+    const outPkgPath = path.resolve(path.join(buildFolder, 'package.json'))
+    const outModulesPath = path.resolve(path.join(buildFolder, 'node_modules'))
+
+    // Link or copy node_modules and package.json to .build so Serverless can
+    // exlcude devDeps during packaging
+    if (!fs.existsSync(outModulesPath)) {
+      await this.linkOrCopy(path.resolve('node_modules'), outModulesPath, 'junction')
     }
 
-    // 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')), 'file')
+    if (!fs.existsSync(outPkgPath)) {
+      await this.linkOrCopy(path.resolve('package.json'), outPkgPath, 'file')
     }
 
     // include any "extras" from the "include" section
@@ -209,6 +212,23 @@ export class TypeScriptPlugin {
     fs.removeSync(path.join(this.originalServicePath, buildFolder))
   }
 
+  /**
+   * Attempt to symlink a given path or directory and copy if it fails with an
+   * `EPERM` error.
+   */
+  private async linkOrCopy(
+    srcPath: string,
+    dstPath: string,
+    type?: 'dir' | 'junction' | 'file'
+  ): Promise<void> {
+    return fs.symlink(srcPath, dstPath, type)
+      .catch(error => {
+        if (error.code === 'EPERM' && error.errno === -4048) {
+          return fs.copy(srcPath, dstPath)
+        }
+        throw error
+      })
+  }
 }
 
 module.exports = TypeScriptPlugin