[local-sync] Correctly close imap connections when downloading files

Summary: Addresses T7708

Test Plan: manual

Reviewers: evan, khamidou, mark, halla

Reviewed By: khamidou, mark, halla

Subscribers: halla

Differential Revision: https://phab.nylas.com/D3795

packages/isomorphic-core/src/imap-box.js

@@ -104,21 +104,22 @@ class IMAPBox {
     })
   }
 
-  fetchMessageStream(uid, options) {
+  fetchMessageStream(uid, {fetchOptions, onFetchComplete} = {}) {
     if (!uid) {
       throw new Error("IMAPConnection.fetchStream requires a message uid.")
     }
-    if (!options) {
+    if (!fetchOptions) {
       throw new Error("IMAPConnection.fetchStream requires an options object.")
     }
     return this._conn._createConnectionPromise((resolve, reject) => {
-      const f = this._conn._imap.fetch(uid, options);
+      const f = this._conn._imap.fetch(uid, fetchOptions);
       f.on('message', (imapMessage) => {
         imapMessage.on('body', (stream) => {
           resolve(stream)
         })
       })
       f.once('error', reject)
+      f.once('end', onFetchComplete || (() => {}));
     })
   }
 

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

@@ -33,8 +33,13 @@ module.exports = (sequelize, Sequelize) => {
           const folder = await message.getFolder()
           const imapBox = await connection.openBox(folder.name)
           const stream = await imapBox.fetchMessageStream(message.folderImapUID, {
-            bodies: this.partId ? [this.partId] : [],
-            struct: true,
+            fetchOptions: {
+              bodies: this.partId ? [this.partId] : [],
+              struct: true,
+            },
+            onFetchComplete() {
+              connection.end()
+            },
           })
           if (!stream) {
             throw new Error(`Unable to fetch binary data for File ${this.id}`)