ActiveRecord 3.1 cannot load models with non-default PKs unless there's already a database connection

database.rb

require 'active_record'
require 'fileutils'

DATABASE_NAME = 'people.sqlite3'

FileUtils.rm_rf DATABASE_NAME, :verbose => true

ActiveRecord::Base.establish_connection :adapter => 'sqlite3', :database => DATABASE_NAME

ActiveRecord::Schema.define do
  create_table :people, :id => false do |t|
    t.primary_key :pid
    t.string :name, :null => false
  end
end

example.rb

require 'bundler'
Bundler.setup

require 'active_record'

def load_models
  puts "Loading models"
  require File.expand_path('../models', __FILE__)
end

def connect_to_database
  puts "Creating and connecting to database"
  require File.expand_path('../database', __FILE__)
end

def models_first?
  ARGV.first =~ /first/
end

def msg
  "on ActiveRecord #{ActiveRecord::VERSION::STRING} with models loaded #{models_first? ? 'first' : 'second'}"
end

begin
  puts "== Running #{msg}"

  if models_first?
    load_models
    connect_to_database
  else
    connect_to_database
    load_models
  end

  Person.create!(:name => 'Jo')
  puts "-- Successful #{msg}!"
rescue => e
  puts "-- Failed #{msg}:"
  raise e
end

Gemfile

source :rubygems

gem 'activerecord', ENV['AR_VERSION'] || '3.1.0'
gem 'sqlite3', '~> 1.3.4'

models.rb

require 'active_record'

class Person < ActiveRecord::Base
  set_primary_key :pid
end

output.txt

$ sh ./run.sh 
ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
Fetching source index for http://rubygems.org/
Using activesupport (3.0.10) 
Using builder (2.1.2) 
Using i18n (0.5.0) 
Using activemodel (3.0.10) 
Using arel (2.0.10) 
Using tzinfo (0.3.29) 
Using activerecord (3.0.10) 
Using sqlite3 (1.3.4) 
Using bundler (1.0.15) 
Your bundle is updated! Use `bundle show [gemname]` to see where a bundled gem is installed.
== Running on ActiveRecord 3.0.10 with models loaded first
Loading models
Creating and connecting to database
rm -rf people.sqlite3
-- create_table(:people, {:id=>false})
   -> 0.0667s
-- Successful on ActiveRecord 3.0.10 with models loaded first!

== Running on ActiveRecord 3.0.10 with models loaded second
Creating and connecting to database
rm -rf people.sqlite3
-- create_table(:people, {:id=>false})
   -> 0.0700s
Loading models
-- Successful on ActiveRecord 3.0.10 with models loaded second!

Fetching source index for http://rubygems.org/
Using multi_json (1.0.3) 
Using activesupport (3.1.0) 
Using bcrypt-ruby (3.0.0) 
Using builder (3.0.0) 
Using i18n (0.6.0) 
Using activemodel (3.1.0) 
Using arel (2.2.1) 
Using tzinfo (0.3.29) 
Using activerecord (3.1.0) 
Using sqlite3 (1.3.4) 
Using bundler (1.0.15) 
Your bundle is updated! Use `bundle show [gemname]` to see where a bundled gem is installed.
== Running on ActiveRecord 3.1.0 with models loaded first
Loading models
-- Failed on ActiveRecord 3.1.0 with models loaded first:
/Users/rsutphin/.rvm/gems/ruby-1.9.2-p290@tmp/gems/activerecord-3.1.0/lib/active_record/attribute_methods/primary_key.rb:69:in `set_primary_key': undefined method `primary_keys' for nil:NilClass (NoMethodError)
	from /private/tmp/ar-cp-pk/models.rb:4:in `<class:Person>'
	from /private/tmp/ar-cp-pk/models.rb:3:in `<top (required)>'
	from example.rb:8:in `require'
	from example.rb:8:in `load_models'
	from example.rb:28:in `<main>'

== Running on ActiveRecord 3.1.0 with models loaded second
Creating and connecting to database
rm -rf people.sqlite3
-- create_table(:people, {:id=>false})
   -> 0.0068s
Loading models
-- Successful on ActiveRecord 3.1.0 with models loaded second!

run.sh

#!/bin/sh

function run_example {
    export AR_VERSION=$1
    bundle update
    bundle exec ruby example.rb first
    echo
    bundle exec ruby example.rb second
    echo
}

echo `ruby -v`
run_example '3.0.10'
run_example '3.1.0'

This is a test case for rails #2807. Clone it, then run run.sh to show that the load order doesn't matter on AR 3.0 but does on AR 3.1.