Sunday, April 21, 2013

Git: patching diffs between branches

Recently I accidentally committed changes to master that I want to commit in a feature branch..... I made the mistake of

  1. branching master (to a feature branch) from my erroneous commit - then
  2. resetting (HARD) master to the previous commit

This axed all my history in my feature branch as the commit which I branched from in master no longer existed....

To fix I had to create a new feature branch from master, then create a patch of the differences between my original feature branch and master doing the following:

git checkout master
git checkout -b [new_feature_branch]
git diff --no-prefix origin/[busted_feature_branch] > my.patch

then apply the patch:

patch -p0 < my.patch

Saturday, April 13, 2013

Javascript: Safely reading a nested property

In some templating frameworks it can be really annoying reading a nested property of a JS object as it can of mean chaining a heap of null checks together....

for instance if I need to access a nested property 'to' in '' safely it means having to do something like:

if(email && (adresses = email.addresses)) {

This is verbose and annoying. I needed a function that would return the nested value, or simply return an empty string if any property in the chain was null or undefined


safeRead(email, 'addresses', 'to');

I also wanted property chains can be as long or short as I'd like.... ie.:

safeRead(my, 'very', 'deeply', 'nested', 'property');

The finished product:

Thursday, April 11, 2013

IE Ajax requests returning 401 Unauthorized in Rails / Sinatra

Here's a quick little nugget of info for any devs experiencing ajax issues in IE....

Firstly, earlier ( <= IE 8) versions of IE cache everything ajax, and it can be a pain to resolve without compromising (breaking through) server side cache.... I wrote an article here about that...

To add another drop to the ocean of pain that is IE, I found that on Windows 7 (and windows 7 only), IE7, IE8 and IE9, all AJAX requests were consistently returning 401 Unauthorized statuses. After much mining through code and system settings etc., a workmate and I discovered that in Windows 7, all ajax requests send an uppercase ACCEPT_LANGUAGE header, whereas regular synchronous requests send a lowercase one.....

This may seem inconsequential, but for those developing a rack based app using rack-protection, this is enough to trip the session-hijacking check, which compares this header with previous requests ( ...

As the case is different the equality check fails, resulting in rack-protection blocking the call and returning 401 Unauthorized.

Not a fun bug.

The solution is to either downcase the header client side for all ajax requests (i.e. $.ajaxSetup), or introduce some custom middleware before rack-protection that downcases the offending header before rack-protection checks it.