make stream generator optional so that directories can be marked as unpacked.

Author: mmaietta

src/asar.ts

@@ -221,10 +221,10 @@ export type Filestream = {
   */
   filePath: string;
   /**
-    function that returns a read stream for the file
-    note: this is called multiple times per "file", so a new NodeJS.ReadableStream will be created each time
+    function that returns a read stream for the file. Not utilized for directories.
+    note: this is called multiple times per "file", so a new NodeJS.ReadableStream needs to be created each time
   */
-  streamGenerator: () => NodeJS.ReadableStream;
+  streamGenerator?: () => NodeJS.ReadableStream;
   properties: {
     /**
       relative path to the symlink target
@@ -257,21 +257,27 @@ export async function createPackageFromStreams(dest: string, filestreams: Filest
         filesystem.insertDirectory(filename, shouldUnpack);
         break;
       case 'file':
+        if (streamGenerator == null) {
+          throw new Error('Stream generator is required for `file` type');
+        }
         files.push({
           filename,
-          streamGenerator,
+          streamGenerator: streamGenerator!,
           link: undefined,
           mode: stat.mode,
           unpack: shouldUnpack,
         });
-        return filesystem.insertFile(filename, streamGenerator, shouldUnpack, {
+        return filesystem.insertFile(filename, streamGenerator!, shouldUnpack, {
           type: 'file',
           stat,
         });
       case 'link':
+        if (streamGenerator == null) {
+          throw new Error('Stream generator is required for `link` type');
+        }
         links.push({
           filename,
-          streamGenerator,
+          streamGenerator: streamGenerator!,
           link: symlink,
           mode: stat.mode,
           unpack: shouldUnpack,