437523 - NS_ERROR_FAILURE on nsIJSON.decode in JsonFilter_afterGET

Status: RESOLVED FIXED

(Cloud Services :: General, defect)

Description

[Myk Melez [:myk] [@mykmelez]]

Attachment: fixes three bugs

I've been seeing errors like this one:

2008-06-05 15:24:56	Service.Main	ERROR	[Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIJSON.decode]"  nsresult: "0x80004005 (NS_ERROR_FAILURE)"  location: "JS frame :: file:///mnt/hgfs/myk/Projects/weave/modules/remote.js :: JsonFilter_afterGET :: line 271"  data: no]

After some digging, I found three separate bugs, all of which cause Weave to encrypt a null value to the deltas file on the server, which, when retrieved, causes nsIJSON.decode to throw the exception.

1. Subclasses of Resource call their superclass's _init method with "this" set to the superclass's prototype rather than the subclass's instance, causing the remote objects for all engines to inherit the serverPrefix for the last engine to instantiate a resource, which entrains a long chain of disasters (like the bookmarks engine, which was instantiated first, trying to apply deltas from the tab engine, which was instantiated last).

2. Engine::_sync pushes serverDelta onto server.deltas instead of concatenating together the two arrays (which I think is a bug, but I'm not sure, as I don't totally understand this code).

3. Engine::_sync passes this._remote.deltas.put a serialized string of deltas rather than the original array.

Here's a patch that fixes all three issues.  With this patch, I no longer see the errors.

Comment 1

[Dan Mills [:thunder]]

Comment on attachment 323947 [details] [diff] [review]
fixes three bugs

Except for:

-      server.deltas.push(serverDelta);
+      server.deltas = server.deltas.concat(serverDelta);

I'm pretty sure that's not right.  server.deltas is an array of deltas, and serverDelta should just get appended to it.

Otherwise, really good detective work on those bugs!

Comment 2

[Myk Melez [:myk] [@mykmelez]]

(In reply to comment #1)
> (From update of attachment 323947 [details] [diff] [review])
> Except for:
> 
> -      server.deltas.push(serverDelta);
> +      server.deltas = server.deltas.concat(serverDelta);
> 
> I'm pretty sure that's not right.  server.deltas is an array of deltas, and
> serverDelta should just get appended to it.

Yup, it looks like the third bug was making the second bug look like a bug, although it wasn't.  I've checked in the patch without that second fix.

changeset:   475:3b2515690ea8
tag:         tip
date:        Thu Jun 05 16:25:55 2008 -0700
summary:     bug 437523: fix NS_ERROR_FAILURE on nsIJSON.decode in JsonFilter_afterGET