Chef/Ruby: Reference to Definition in Hash

Question

The code below works as expected and produces the following:

==> default: foo_definition: a
==> default: foo_definition: foo
==> default: foo_definition: fiz
==> default: bar_definition: b
==> default: bar_definition: bar
==> default: bar_definition: biz

cookbooks/foobar/recipes/default.rb:

node.default[:configs][:a][:def_name] = 'foo_name'
node.default[:configs][:a][:message] = 'fiz'
node.default[:configs][:b][:def_name] = 'bar_name'
node.default[:configs][:b][:message] = 'biz'

#def_map = {
#       'foo_name' => foo_definition,
#       'bar_name' => bar_definition
#}

for config_name in node[:configs].keys do
        def_name = node[:configs][config_name][:def_name]

        if def_name == 'foo_name'
                foo_definition config_name do
                        config_name config_name
                end
        elsif def_name == 'bar_name'
                bar_definition config_name do
                        config_name config_name
                end
        else
                raise Exception('Unknown def #{def_name}')
        end
end

cookbooks/foobar/definitions/default.rb:

define :foo_definition, :config_name => nil do
        config_name = params[:config_name]
        print("foo_definition: #{config_name}")
        print("foo_definition: #{node[:configs][config_name][:def_name]}")
        print("foo_definition: #{node[:configs][config_name][:message]}")
end

define :bar_definition, :config_name => nil do
        config_name = params[:config_name]
        print("bar_definition: #{config_name}")
        print("bar_definition: #{node[:configs][config_name][:def_name]}")
        print("bar_definition: #{node[:configs][config_name][:message]}")
end

I'd like to use a hash to lookup the specific definition named in the config. But, if I uncomment the def_map, Chef complains:

==> default: NoMethodError
==> default: -------------
==> default: undefined method `[]' for nil:NilClass
==> default: 
==> default: 
==> default: Cookbook Trace:
==> default: ---------------
==> default: /tmp/vagrant-chef/2e4e554824398d9416eee0b4bd47e8b9/cookbooks/foobar/definitions/default.rb:4:in 'block in from_file'

Anyone out there able to explain why?

Ultimately I'd like to be able to do something like this in the recipe:

node.default[:configs][:a][:def_name] = 'foo_name'
node.default[:configs][:a][:message] = 'fiz'
node.default[:configs][:b][:def_name] = 'bar_name'
node.default[:configs][:b][:message] = 'biz'

def_map = {
        'foo_name' => foo_definition,
        'bar_name' => bar_definition
}

for config_name in node[:configs].keys do
        def_name = node[:configs][config_name][:def_name]
        if def_map.key?(def_name)
                named_def = def_map[def_name]
                named_def config_name do
                        config_name config_name
                end
        else
                raise Exception('Unknown def #{def_name}')
        end
end

Answer 1

You definition takes an argument named :config_name

define :foo_definition, :config_name => nil do

And you call it without any argument in your def_map:

 'foo_name' => foo_definition,

So when the definition is called there (in you map), config_name is nil, and this line

print("foo_definition: #{node[:configs][config_name][:def_name]}")

is called as:

print("foo_definition: #{node[:configs][nil][:def_name]}")

---

A workaround could be to use this kind of code (untested):

for config_name in node[:configs].keys do
        def_name = node[:configs][config_name][:def_name]
        send(def_name) config_name do
                        config_name config_name
        end
end

If the definition is not known in the recipe context, this should raise an exception, you may wrap it in a try/catch block if you want to not abort the run and just log about it.