[local-sync] Fix setlabels task

Make sure we /remove/ the labels when we get an empty set of label ids

packages/local-sync/src/local-sync-worker/syncback_tasks/set-thread-labels.imap.js

@@ -10,14 +10,22 @@ class SetThreadLabelsIMAP extends SyncbackTask {
     const threadId = this.syncbackRequestObject().props.threadId
     const labelIds = this.syncbackRequestObject().props.labelIds
 
-    const labels = await db.Label.findAll({where: {id: labelIds}});
-    const gmailLabelIdentifiers = labels.map((label) => {
-      if (label.role) {
-        return `\\${label.role[0].toUpperCase()}${label.role.slice(1)}`
-      }
-      return label.name;
-    });
+    if (!labelIds || labelIds.length === 0) {
+      return TaskHelpers.forEachMessageInThread({
+        db,
+        imap,
+        threadId,
+        callback: ({message, box}) => {
+          return message.getLabels().then((labels) => {
+            const labelIdentifiers = labels.map(label => label.imapLabelIdentifier())
+            return box.removeLabels(message.folderImapUID, labelIdentifiers)
+          })
+        },
+      })
+    }
 
+    const labels = await db.Label.findAll({where: {id: labelIds}});
+    const labelIdentifiers = labels.map(label => label.imapLabelIdentifier());
 
     // Ben TODO this is super inefficient because it makes IMAP requests
     // one UID at a time, rather than gathering all the UIDs and making
@@ -27,7 +35,7 @@ class SetThreadLabelsIMAP extends SyncbackTask {
       imap,
       threadId,
       callback: ({message, box}) => {
-        return box.setLabels(message.folderImapUID, gmailLabelIdentifiers)
+        return box.setLabels(message.folderImapUID, labelIdentifiers)
       },
     })
   }

packages/local-sync/src/models/label.js

@@ -36,7 +36,14 @@ module.exports = (sequelize, Sequelize) => {
       },
     },
     instanceMethods: {
-      toJSON: function toJSON() {
+      imapLabelIdentifier() {
+        if (this.role) {
+          return `\\${this.role[0].toUpperCase()}${this.role.slice(1)}`
+        }
+        return this.name;
+      },
+
+      toJSON() {
         return {
           id: `${this.id}`,
           account_id: this.accountId,