How to tell Chef to take an action if the desired package to install doesn't exist?

Question

I'm trying to get Chef to perform the following:

• Check if the desired debian (can be any package really) is available
• If it is, apt-get install the package
• If it's not, build the package using the source

I know you can do:

remote_file "some remote file" do
  ...
  not_if "apt-cache search 'mypackage'"
end

However, I tried:

ruby_block "Attempting to install #{node[:bact][:application_name]}" do
  block do
    cmd = Chef::ShellOut.new("apt-get install -y --force-yes #{node[:bact][:application_name]}")
    exec_result = cmd.run_command
    if exec_result.exitstatus != 0
      Chef::Log.info 'Go grab some coffee, this might be a while....'
      resources("execute[install-#{node[:bact][:application_name]}-via-pip]").run_action(:run)
    end
  end
  action :create
end

Is there an easier and less uglier way to do this?

Basically, what I'd ideally like to do is:

begin
   package 'some-package-name' do
     action :install
   done
rescue Chef::Exception
   # Do something here
end

Answer 1

You could install the Debian package using ignore_failure true. Then you can install the pip package only if the Debian package is not installed at this point. This could look something like this:

package node[:bact][:application_name] do
  ignore_failure true
end

# Resource available from the opscode python cookbook
python_pip node[:bact][:application_name] do
  # Install the pip package only if the debian package is not installed
  not_if "dpkg-query -W '#{node[:bact][:application_name]}'"
end