[chef] Re: Re: Re: Re: Re: Re: Re: Re: Re: any plan for partial templates in Chef?


Chronological Thread 
  • From: Andrea Campi < >
  • To: " " < >
  • Subject: [chef] Re: Re: Re: Re: Re: Re: Re: Re: Re: any plan for partial templates in Chef?
  • Date: Wed, 14 Nov 2012 22:52:00 +0100

On Wed, Nov 14, 2012 at 3:29 AM, Daniel DeLeo < " target="_blank"> > wrote:

About the implementation, using the lambda as the partial finder is clever, but it'd be nice if it could be done with less magic.


On Wed, Nov 14, 2012 at 8:36 AM, Bryan Berry < " target="_blank"> > wrote:
echoing Dan's comment on the lambda, why not just make  partial_resolver  a method inside Chef::Mixin::Template::ChefContext next to your render method ?   Do you need the late binding that the lambda gives you?  

Chef::Mixin::Template::ChefContext is a "clean slate" that is very careful to expose as little data as possible to the template, so unfortunately that wouldn't work.
Chef::Mixin::Template is not possible either, since by design it doesn't know anything about nodes, run contexts and so on. That has value in unit testing and futher.

So a closure is a given, I think.

What I plan to do to make this more readable is to turn the body of the lambda into a proper method of Chef::Provider::Template. We will still need to pass a proc / lambda into the options hash, but it will be less magic.



also, why do you have an if statement in the following, do you expect the partial_resolver to be pluggable or somehow converted to nil ? 

+          if @partial_resolver
+            template_location = @partial_resolver.call(partial_name)
+            eruby = Erubis::Eruby.new(IO.read(template_location))
+            output = eruby.evaluate(self)
+          else
+            "foo"
+          end

Yes, kinda. This is defining an API of sorts—it enables any caller of Chef::Mixin::Template::ChefContext to specify this partial_resolver, but they don't have to, it's up to them.

If I dropped the if and somebody invoked this "incorrectly", you would get something hard to debug.
If instead I replaced "foo" with something like:

raise "You cannot render a partial in this context"

at least you would have a clear hint of what went wrong.


But I have to say, this is pretty hypotetical: in the tree today we have exactly two uses for this mixin: Chef::Provider::Template, and specs.




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