only invoke callback once

Author: stephenplusplus

lib/storage/file.js

@@ -26,6 +26,7 @@ var crc = require('fast-crc32c');
 var crypto = require('crypto');
 var duplexify = require('duplexify');
 var fs = require('fs');
+var once = require('node-once');
 var request = require('request');
 var streamEvents = require('stream-events');
 var through = require('through2');
@@ -649,6 +650,8 @@ File.prototype.download = function(options, callback) {
     options = {};
   }
 
+  callback = once(callback);
+
   var destination = options.destination;
   delete options.destination;
 

package.json

@@ -51,6 +51,7 @@
     "fast-crc32c": "^0.1.3",
     "google-service-account": "^1.0.3",
     "mime-types": "^2.0.3",
+    "node-once": "0.0.1",
     "node-uuid": "^1.4.1",
     "protobufjs": "^3.4.0",
     "request": "^2.39.0",

test/storage/file.js

@@ -787,6 +787,17 @@ describe('File', function() {
       file.download(readOptions, assert.ifError);
     });
 
+    it('should only execute callback once', function(done) {
+      fileReadStream._read = function() {
+        this.emit('error', new Error('Error.'));
+        this.emit('error', new Error('Error.'));
+      };
+
+      file.download(function() {
+        done();
+      });
+    });
+
     describe('into memory', function() {
       it('should buffer a file into memory if no destination', function(done) {
         var fileContents = 'abcdefghijklmnopqrstuvwxyz';