Saturday, 27 October 2012

[SOLVED] undefined method `name' for "Ascii85":String

So, we're still using Rails 2.3.2 for our client... but I'm *trying* to upgrade it piece by piece. In doing so, I recently had to upgrade rubygems, so that it would work with a recent version of a gem we desperately needed.

Unfortunately it led to the undefined method `name' for "Ascii85":String bug that I wrote about when I last tried to upgrade rubygems

Back when it broke rubygems the first time, the only solution seemed to be to downgrade rubygems and hope for a future time when I could upgrade everything and get it working again.

But that wasn't an option this time... and so I had to hack up a solution.

The problem is described below in solution 2, but it's basically a problem with rails - which isn't using the newer rubygems gem-comparing "==" function properly any more.

Solution 1: Gem bundler

One solution that definitely works is to upgrade to using gem bundler (or the Rails2.3 version of bundler).

This definitely works because bundler doesn't have the same bug in it that Rails 2 has - it uses gem-comparison the new way.

But some of our clients aren't on the bundled release yet, and I need to quickly fix bugs and push to those clients... so I needed a solution that would let me still load the bundler-free version without having to downgrade rubygems to do it.

Solution 2: Fix rails

This solution requires a (very small) hack on Rails... but I figured that was ok as it was just to get my own system working so I can fix things without having to go through the pain of installing rvm (which I don't have time for right now).

So far the fix seems to be working, so I'll share (with the caveat that it's not well tested yet so YMMV).

The problem is really a Rails bug... not rubygems. So that's where you can safely hack (for now). From the stacktrace of the bug, find the copy of "rails/gem_dependency.rb" that is causing the issue:

/usr/lib/ruby/gems/1.8/gems/rails-2.3.2/lib/rails/gem_dependency.rb:239:in `==': 
undefined method `name' for "Ascii85":String (NoMethodError)
 from /usr/local/lib/site_ruby/1.8/rubygems/dependency.rb:218:in `==='

In my case, I opened /usr/lib/ruby/gems/1.8/gems/rails-2.3.2/lib/rails/gem_dependency.rb in a text editor (with sudo permissions). It'll have something like the following:

    def ==(other)
      self.name == other.name && self.requirement == other.requirement
    end

The actual problem occurs because Rails is sometimes passing the name already as a string to this function, instead of an actual spec. So to fix it, we just check for that with the following code:

    def ==(other)
      # The following line has been inserted to get around the bug:
      # "undefined method `name' for "Ascii85":String (NoMethodError)"
      return self.name == other if other.is_a?(String) # bugfix
      self.name == other.name && self.requirement == other.requirement
    end

It shouldn't alter existing functionality, it'll just get past the broken code that is in rails until you can upgrade rails, or use bundler.

If you (horror) actually need to install this fix on a live system; I'd recommend freezing rails to your gems directory before applying the fix. But in reality, I'd actually recommend just finding a way to upgrade to using bundler. It's a neater solution that won't require ongoing maintenance.

Sunday, 21 October 2012

Link: Primer on sexism in the tech-industry

"The topic of sexism and its role in the technology industry has seen a huge resurgence over the past 12 to18 months. Yet despite being discussed and examined with increasing frequency, a lot of the subject remains unclear and under-explained, making it difficult for those who care deeply about our industry to partake in these discussions. This is, in part, because the problems are incredibly complex, nuanced and difficult to explain, making it impossible for any one article to address them sufficiently (lest that article becomes a book). Nevertheless, today we're going to try and see how much of the basics we can clear up."

Faruk AteĊŸ has written a most-excellent primer on sexism in the tech industry

You should read this (especially if you are male) before even considering posting an article or comment about women in the tech industry.

Monday, 15 October 2012

Making views/triggers/functions work in mysql for rails

We use mysql with Rails. We also use foreign-keys, views, triggers and stored procedures.

Rails's mysql gem still doesn't know how to handle any of the above yet... which is kind of inconvenient if you want to test your application.

The problem arises because even with a SQL schema dump - it only dumps the tables and foreign keys. No views, no triggers, no stored procedures. If you have code that relies on these... your application starts getting MySql errors.

Luckily there seems to be a solution with the db_structure_ext gem, which I've been using happily now for a couple of weeks.

I found the README isn't at all clear as to how to get it set up, so here's some basic instructions on how I made it work with MySQL on Rails 2.3.X

1) Install it as per the README:

gem install db_structure_ext and/or add gem 'db_structure_ext' to Gemfile and then bundle install

2) require it in your Rakefile

# extended db-structure-dump (also does triggers, routines etc)
require 'db_structure_ext/tasks'

3) Monkey-patch ActiveRecord

Create a file call config/initializers/mysql_adapter.rb (or similar) and add the following code:


module ActiveRecord
  module ConnectionAdapters
    class MysqlAdapter
      require 'db_structure_ext/init_mysql_adapter'

      # This is an overridden implementation of the structure_dump so that the
      # rake take db:structure:dump will dump out the schema elements.
      def structure_dump
        connection_proxy = DbStructureExt::MysqlConnectionProxy.new(ActiveRecord::Base.connection)
        connection_proxy.structure_dump
      end

    end
  end
end

You need this so that Active Record actually extends the new methods. If you don't do this, then you can call "structure_dump" yourself in your code, independently for certain tables. But the new functionality won't come through as the default for all of your db tables unless you extend MysqlAdapter as per above.

Tuesday, 9 October 2012

Link: Women at work in Silicon Valley

Balancing work with family is one of the Hard Problems of Social Engineering a career... especially if you're female, and already suffer from several disadvantages in a high-tech workplace.

This article on The Guardian gives a great overview about how women in Silicon valley are making "Women at work" work.