fix(file-drop): Wait for attachments before popping composer

internal_packages/attachments/package.json

@@ -12,6 +12,7 @@
   },
   "windowTypes": {
     "default": true,
-    "composer": true
+    "composer": true,
+    "composer-preload": true
   }
 }

src/flux/stores/draft-store.coffee

@@ -299,10 +299,20 @@ class DraftStore
 
   _onHandleMailFiles: (event, paths) =>
     DraftFactory.createDraft().then (draft) =>
-      @_finalizeAndPersistNewMessage(draft, popout: true)
+      @_finalizeAndPersistNewMessage(draft)
     .then ({draftClientId}) =>
+      remaining = paths.length
+      callback = =>
+        remaining -= 1
+        if remaining is 0
+          @_onPopoutDraftClientId(draftClientId)
+
       for path in paths
-        Actions.addAttachment({filePath: path, messageClientId: draftClientId})
+        Actions.addAttachment({
+          filePath: path,
+          messageClientId: draftClientId,
+          callback: callback
+        })
 
   _onDestroyDraft: (draftClientId) =>
     session = @_draftSessions[draftClientId]

src/flux/stores/file-upload-store.coffee

@@ -59,7 +59,9 @@ class FileUploadStore extends NylasStore
       pathsToOpen.forEach (filePath) ->
         Actions.addAttachment({messageClientId, filePath})
 
-  _onAddAttachment: ({messageClientId, filePath}) ->
+  _onAddAttachment: ({messageClientId, filePath, callback}) ->
+    callback ?= ->
+
     @_verifyId(messageClientId)
     @_getFileStats({messageClientId, filePath})
     .then(@_makeUpload)
@@ -69,6 +71,7 @@ class FileUploadStore extends NylasStore
     .then (upload) =>
       @_applySessionChanges upload.messageClientId, (uploads) ->
         uploads.concat([upload])
+    .then(callback)
     .catch(@_onAttachFileError)
 
   _onRemoveAttachment: (upload) ->
@@ -145,10 +148,4 @@ class FileUploadStore extends NylasStore
       uploads = changeFunction(session.draft().uploads)
       session.changes.add({uploads})
 
-      # In some scenarios (like dropping attachments on the dock icon), files
-      # are added to drafts which may be open in another composer window.
-      # Committing here ensures the files appear immediately, no matter where the
-      # user is now viewing the draft.
-      session.changes.commit()
-
 module.exports = new FileUploadStore()