[chef] Re: variable scope in LWRPs

[Daniel DeLeo < >]

On Sunday, May 10, 2015 at 12:07 PM, Johannes Kleinlercher wrote:

> Hi all,
> I have the following problem and I think its because I do not understand 
> the variable scopes in Chef LWRPs.
> You can look at the cookbook at 
> https://github.com/jkleinlercher/chef_problems and simply test the ;
> behaviour with kitchen.
> Even though I define the following very similar resources, I recognized, 
> that the attribute 'colors' inherits from the previous defined resources. 
> The attribute 'colors' is defaulted to "['blue']" and in the provider the 
> element 'magenta' is added to the array. However, the second and third 
> resource inherit the whole array from the previous resource. That is quite 
> weird to me ...
> Resource definition in recipes/default.rb:
> chef_problems_problem1 "test1" do address "myaddress1" action :install end 
> chef_problems_problem1 "test2" do address "myaddress2" action :install end 
> chef_problems_problem1 "test3" do address "myaddress3" action :install end
> In the output of the kitchen converge you see that the variable 
> new_resource.colors inherits the values of the previous resources:
> * chef_problems_problem1[test1] action install new_resource.colors at the 
> beginning: ["blue"] Values of local variables: address: myaddress1 colors: 
> ["blue"] adding magenta to local variable colors colors after adding 
> magenta: ["blue", "magenta"] new_resource.colors at the end: ["blue", 
> "magenta"] * chef_problems_problem1[test2] action install 
> new_resource.colors at the beginning: ["blue", "magenta"] Values of local 
> variables: address: myaddress2 colors: ["blue", "magenta"] adding magenta 
> to local variable colors colors after adding magenta: ["blue", "magenta", 
> "magenta"] new_resource.colors at the end: ["blue", "magenta", "magenta"] * 
> chef_problems_problem1[test3] action install new_resource.colors at the 
> beginning: ["blue", "magenta", "magenta"] Values of local variables: 
> address: myaddress3 colors: ["blue", "magenta", "magenta"] adding magenta 
> to local variable colors colors after adding magenta: ["blue", "magenta", 
> "magenta", "magenta"] new_resource.colors at the end: ["blue", "magenta", 
> "magenta", "magenta"]
> Maybe you can help me to find where the problem is here.
>  
> best regards,  
> Johannes

I think this is a bug. I think default value in this line: 
https://github.com/jkleinlercher/chef_problems/blob/fe42785a400cc154b75112b2d92f6136c60c0f08/resources/problem1.rb#L7
 is reused for each resource. Then when you mutate it in this line: 
https://github.com/jkleinlercher/chef_problems/blob/fe42785a400cc154b75112b2d92f6136c60c0f08/providers/problem1.rb#L12
 you’re updating the one array object.

You can confirm this by printing the object_id of the array in your debug 
logging. You should be able to work around it by calling dup on the array, or 
setting the default value in an initialize method instead of via the DSL.

--  
Daniel DeLeo