Trouble combining element in 'each' do block with node attribute

Question

I'm using Chef 11.10.4 running in AWS Opsworks.

I can't figure out how to combine the element lyr with the node attribute node['aws-tag'][#{lyr}] in lines 07-14 below.

I'm using a string substitution as pseudo code to show what I'm trying to do but it obviously doesn't work in this situation. Lines 02-06 work perfectly, I'm just trying to get lines 07-14 working and I don't know how to do it.

include_recipe "aws"
unless node['aws-tag']['tags'].empty? || node['aws-tag']['tags'].nil?
   aws_resource_tag node['ec2']['instance_id'] do
       tags(node['aws-tag']['tags'])
       action :update
   end
   node['opsworks']['instance']['layers'].each do |lyr|
       unless node['aws-tag'][#{lyr}].empty? || node['aws-tag'][#{lyr}].nil?
           aws_resource_tag node['ec2']['instance_id'] do
               tags(node['aws-tag'][#{lyr}])
               action :update
           end
       end
   end
end

Here are the results from chef-shell showing the values of the attributes referenced in the code above:

chef > node['opsworks']['instance']['layers']
 => ["mongodb"]

chef > node['aws-tag']
 => {"tags"=>{"application"=>"app1", "environment"=>"dev"}, "mongodb"=>{"service"=>"mongodb"}}

I'm modifying the chef-aws-tag cookbook to tag all ec2 instances with the tags in node['aws-tag']['tags'] and in addition to tag each ec2 instance opsworks layer specific tags that are included in custom JSON passed to opsworks by layer, in this case the contents of node['aws-tag']['mongodb'] or node['aws-tag']['LAYER'], generically.

If I run the code above I get a recipe compile error: "unexpected keyword_do_block, expecting ']'" -- see below for the detailed error message from opsworks:

================================================================================
Recipe Compile Error in /var/lib/aws/opsworks/cache.stage2/cookbooks/chef-aws-tag/recipes/ec2.rb
================================================================================


SyntaxError
-----------
/var/lib/aws/opsworks/cache.stage2/cookbooks/chef-aws-tag/recipes/ec2.rb:9: syntax error, unexpected keyword_do_block, expecting ']'
/var/lib/aws/opsworks/cache.stage2/cookbooks/chef-aws-tag/recipes/ec2.rb:12: syntax error, unexpected keyword_end, expecting ']'


Cookbook Trace:
---------------
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/mixin/from_file.rb:30:in `instance_eval'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/mixin/from_file.rb:30:in `from_file'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/cookbook_version.rb:237:in `load_recipe'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context.rb:151:in `load_recipe'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context/cookbook_compiler.rb:139:in `block in compile_recipes'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context/cookbook_compiler.rb:137:in `each'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context/cookbook_compiler.rb:137:in `compile_recipes'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context/cookbook_compiler.rb:74:in `compile'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/run_context.rb:86:in `load'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/policy_builder/expand_node_object.rb:75:in `setup_run_context'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/client.rb:252:in `setup_run_context'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/client.rb:413:in `do_run'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/client.rb:200:in `block in run'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/client.rb:194:in `fork'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/client.rb:194:in `run'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/application.rb:215:in `run_chef_client'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/application/client.rb:314:in `block in run_application'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/application/client.rb:306:in `loop'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/application/client.rb:306:in `run_application'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/application.rb:66:in `run'
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/bin/chef-client:26:in `<top (required)>'
/opt/aws/opsworks/current/bin/chef-client:16:in `load'
/opt/aws/opsworks/current/bin/chef-client:16:in `<main>'


Relevant File Content:
----------------------
/opt/aws/opsworks/releases/20141010064749_328/vendor/bundle/ruby/2.0.0/gems/chef-11.10.4/lib/chef/mixin/from_file.rb:

23: 
24:        # Loads a given ruby file, and runs instance_eval against it in the context of the current
25:        # object.
26:        #
27:        # Raises an IOError if the file cannot be found, or is not readable.
28:        def from_file(filename)
29:          if File.exists?(filename) && File.readable?(filename)
30>>           self.instance_eval(IO.read(filename), filename, 1)
31:          else
32:            raise IOError, "Cannot open or read #{filename}!"
33:          end
34:        end
35: 
36:        # Loads a given ruby file, and runs class_eval against it in the context of the current
37:        # object.
38:        #
39:        # Raises an IOError if the file cannot be found, or is not readable.



[2014-10-28T17:43:22+00:00] ERROR: Running exception handlers
[2014-10-28T17:43:22+00:00] ERROR: Exception handlers complete
[2014-10-28T17:43:22+00:00] FATAL: Stacktrace dumped to /var/lib/aws/opsworks/cache.stage2/chef-stacktrace.out
[2014-10-28T17:43:22+00:00] ERROR: /var/lib/aws/opsworks/cache.stage2/cookbooks/chef-aws-tag/recipes/ec2.rb:9: syntax error, unexpected keyword_do_block, expecting ']'
/var/lib/aws/opsworks/cache.stage2/cookbooks/chef-aws-tag/recipes/ec2.rb:12: syntax error, unexpected keyword_end, expecting ']'
[2014-10-28T17:43:22+00:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

Answer 1

lyr is already a string so the following works:

node['opsworks']['instance']['layers'].each do |lyr|
    unless node['aws-tag'][lyr].empty? || node['aws-tag'][lyr].nil?
        aws_resource_tag node['ec2']['instance_id'] do
            tags(node['aws-tag'][lyr])
            action :update
        end
    end
end

I tested this in chef-shell interactively and it didn't work but I guess there is some difference when executing it at runtime because it does work there. Here is the output of my test that failed in chef-shell that I thought was the same thing:

root@mongodb2:/opt/aws/opsworks/current/bin# ./chef-shell -j /var/lib/aws/opsworks/chef/2014-10-28-17-15-30-01.json
loading configuration: none (standalone session)
Session type: standalone
Loading.......done.

This is the chef-shell.
 Chef Version: 11.10.4
 http://www.opscode.com/chef
 http://docs.opscode.com/

run `help' for help, `exit' or ^D to quit.

Ohai2u ubuntu@mongodb2.localdomain!
chef > lyr=node['opsworks']['instance']['layers']
 => ["mongodb"]
chef > lyr
 => ["mongodb"]
chef > node['aws-tag'][lyr]
 => nil
chef >