add_htpasswd_users.rb

define :add_htpasswd_users do
  params[:users].each do |auth|
    execute "add_htpasswd_#{auth[:username]}" do
      command "echo '#{auth[:username]}:#{auth[:password]}' >> #{params[:name]}"
      not_if do
        if File.exists?(params[:name])
          File.open(params[:name]) do |password_file|
            password_file.detect { |line| line =~ /#{auth[:username]}:#{auth[:password]}/ }
          end
        end
      end
    end
  end
end

attributes.rb

# attributes
nagios Mash.new
nagios[:users] = Array.new
nagios[:users] << {:username => "admin", :password => "whatever"}

default.rb

Chef::Log.debug("node = #{node}")
Chef::Log.debug("node[:nagios] = #{node[:nagios].inspect}")
Chef::Log.debug("node[:nagios][:users] = #{node[:nagios][:users].class}, #{node[:nagios][:users].inspect}")

# works
blah = node[:nagios][:users]
add_htpasswd_users "/tmp/out" do
  users(blah)
end

# broken
# /var/chef/cache/cookbooks/testing/recipes/default.rb:32:in `[]': Symbol as array index (TypeError)
add_htpasswd_users "/tmp/out" o
  users(node[:nagios][:users])
end