Painful ruby 1.9.2-p180 to 1.9.2-p290 upgrade

I did the recommended upgrade of my current p180 to the new p290 using rvm:

$ rvm upgrade ruby-1.9.2-p180 ruby-1.9.2-p290

First annoyance – moving gems from one gemset to the new one took over 40 minutes. Have really no idea why.

But after it was done, whenever I tried to run ‘gem’ or ‘rake’ or ‘bundle’ I got:

Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/guard-0.8.1.gemspec]: invalid date format in specification: "2011-09-29 
00:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/json-1.6.1.gemspec]: invalid date format in specification: "2011-09-18 0
0:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/heroku-2.8.4.gemspec]: invalid date format in specification: "2011-09-23
 00:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/guard-0.8.4.gemspec]: invalid date format in specification: "2011-10-03 
00:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/multi_xml-0.4.0.gemspec]: invalid date format in specification: "2011-09
-06 00:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/heroku-2.8.1.gemspec]: invalid date format in specification: "2011-09-21
 00:00:00.000000000Z"
Invalid gemspec in [/home/jkl/.rvm/gems/ruby-1.9.2-p290/specifications/metrical-0.0.7.gemspec]: invalid date format in specification: "2011-09-
11 00:00:00.000000000Z"
...
and so on...

The above is another manifestation of the YAML engine switch from Syck to Psych and all of the incompatibilities it has brought. The problem is that now you have to reinstall all of your gems, because all installed gems have wrong gemspec specification. D’oh.

I fixed it by running:

$ rvm gemset empty

And then bundling in each project…

$ bundle

Some more reading material.

Bug of the day

Completely bad code follows, beware.

Silent error in Ruby 1.8.7:

x = [:a, :b]
=> [:a, :b]

x.slice!(:a)
=> nil

x
=> [:a, :b]

Explicit error (resulting in a failing test) in Ruby 1.9.2:

x = [:a, :b]
=> [:a, :b]

x.slice!(:a)
TypeError: can't convert Symbol into Integer

Just yet another incompatibility, but for the better!

Run guard-jasmine-headless-webkit without X server

You write specs for your javascript, right? If not, you really should.

jasmine-headless-webkit really helps with that. guard-jasmine-headless-webkit makes it all even more enjoyable, although there’s one caveat – it’s not so easy to set it all up.

There is a great guide for that, but it lacks some important details on running guard-jasmine-headless-webkit without graphical interface (X server).

Assuming you already have Xvfb installed, execute this command to run Xvfb in the background:

Xvfb :0 -screen 0 1024x768x24 > /dev/null 2>&1 &

And then you need to setup the DISPLAY shell variable in order for guard-jasmine-headless-webkit to automatically connect to our virtual frame buffer. Here’s the excerpt from my .bash_profile (it first checks if there is Xvfb running on display :0 and only then sets the DISPLAY variable):

xdpyinfo -display :0 &>/dev/null && export DISPLAY=:0

Hash to HTML (hash2html) in Ruby

I needed to output a Hash as a nested HTML structure. Googling didn’t find any satisfactory results, so I decided to roll my own. UL/LI tags seemed like the best choice. It was a nice exercise in recursion.

The result is a function, which outputs a nicely indented HTML. Note, however, that it’s a very basic solution. It doesn’t cope well with anything other than Strings and Numbers (unless your objects support a nice to_s method).

# Prints nested Hash as a nested <ul> and <li> tags
# - keys are wrapped in <strong> tags
# - values are wrapped in <span> tags
def HashToHTML(hash, opts = {})
  return if !hash.is_a?(Hash)

  indent_level = opts.fetch(:indent_level) { 0 }

  out = " " * indent_level + "<ul>\n"

  hash.each do |key, value|
    out += " " * (indent_level + 2) + "<li><strong>#{key}:</strong>"

    if value.is_a?(Hash)
      out += "\n" + HashToHTML(value, :indent_level => indent_level + 2) + " " * (indent_level + 2) + "</li>\n"
    else
      out += " <span>#{value}</span></li>\n"
    end
  end

  out += " " * indent_level + "</ul>\n"
end

Who knows, maybe someone somewhere finds it useful.

Update: much more concise solution by Piotr Szotkowski.

hookup is the shit!

This is simply amazing:

$ g pull
Already up-to-date.

$ g co edge
Switched to branch 'edge'
==  AddFileTypeToSong: migrating ==============================================
-- add_column(:songs, :file_type, :string)
   -> 0.0048s
==  AddFileTypeToSong: migrated (0.1380s) =====================================

$ g rebase master
Current branch edge is up to date.

$ g co master
Switched to branch 'master'
==  AddFileTypeToSong: reverting ==============================================
-- remove_column(:songs, :file_type)
   -> 0.1674s
==  AddFileTypeToSong: reverted (0.1679s) =========================

Oh, and it will bundle automatically for you as well, so don’t hesitate and hookup your Rails project!

On Heroku

While Heroku is nice and all, it suffers from the same disease as every other hosted-for-you solution:

$ git push heroku
(...)
-----> Gemfile detected, running Bundler version 1.0.7
(...)

$ bundle --version
Bundler version 1.0.10

It’s a whole three patch versions behind! Now I don’t really know (and maybe don’t even really want to know) what has changed between .7 and .10, but I can easily imagine things braking precisely because those minor inconsistencies in Bundler versions.

And sure, I could downgrade to .7, but to do that just because of Heroku? Thank you, but no. I want to ride the latest.

Mocha. The stubbing library

This example (shortened here):

class Order
  def shipping_cost
    total_weight * 5 + 10
  end
end

require 'test/unit'
require 'rubygems'
require 'mocha'

class OrderTest < Test::Unit::TestCase
  # illustrates stubbing instance method
  def test_should_calculate_shipping_cost_based_on_total_weight
    order = Order.new
    order.stubs(:total_weight).returns(10)
    assert_equal 60, order.shipping_cost
  end
end

and this snippet (emphasis mine):

The more interesting discussion deals with whether to mock or stub your database-backed model. One upside is speed: This test case will not hit the database at all. Another is independence. I completely isolate the code under test to the controller layer.

convinced me that there just might be some treasure to be found beyond the Test::Unit. And I know that it's just the tip of the iceberg.