1328616 - storage.local.get returns array instead of object in Firefox <=51

Status: RESOLVED WONTFIX

(Developer Documentation Graveyard :: Add-ons, defect, P2)

Description

[Geoffrey De Belie (Smile4ever)]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0
Build ID: 20161213204721

Steps to reproduce:

https://github.com/Smile4ever/firefoxaddons/blob/f1ce137a8d7a3ceaf1a242e0c58abb1dd76b88de/Scrollkey-webext/scrollkey.js

Important parts from the code:

var getScrollValue = function(id) -> storage.local.get is called
var value = function(result) -> the result is processed. Note the if(isLowFirefoxVersion()) as a workaround for this (suspected) bug.



Actual results:

storage.local.get returns an array in Firefox <=51

[{
  "key": "value"
}]

In Firefox >=52 this works correctly and an object is returned (see below).


Expected results:

storage.local.get should return an object:

{
  "key": "value"
}

Comment 1

[Bob Silverberg [:bsilverberg]]

I just did a quick test on Firefox 50.1 and I do get an object back from storage.local.get. Can you create a reduced test case that reproduces this behaviour on Firefox < 52?

Comment 2

[Geoffrey De Belie (Smile4ever)]

Attachment: TestLocalStorage-source.zip

Test case. Output with Firefox 50.1.0:

Getting result..  testlocalstorage.js:16:2
An array  testlocalstorage.js:18:3
[{"scrollvalue":600}]  testlocalstorage.js:22:2

Source (zip also contains manifest):
var onSuccess = function(result){
	console.log("Getting result..");
	if(Array.isArray(result)){
		console.log("An array");
	}else{
		console.log("Not an array");
	}
	console.log(JSON.stringify(result));
}

var onError = function(result){
	
}

browser.storage.local.set({
	scrollvalue: 600
});
var getting1 = browser.storage.local.get("scrollvalue");
getting1.then(onSuccess, onError);

Comment 3

[Bob Silverberg [:bsilverberg]]

It is reproducible when run from a content script, but not when run from a background script, and I can see that on Firefox 50.1 an array is returned while on 53 an object is returned, so this does look like a bug. I'll leave it to be triaged in case anyone else has any quick ideas about what the cause may be, and whether a fix needs to be uplifted. Thanks Geoffrey.

Comment 4

[:shell escalante]

believe regression introduced and then fixed in 52.  Timing wise we won't be able to uplift into Beta before 51 goes to release.  Add to release notes.  Matt Wein will document

Comment 5

[:shell escalante]

matt will write up docs to let folks know issue in 51.

Comment 6

[Matthew Wein [:mattw]]

This is already documented in the warning box at https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/storage/StorageArea/get.

Comment 7

[Matthew Wein [:mattw]]

Thanks to Makyen for adding in the documentation