args, key=value pairs and task yaml

[Kamil Paral]

> It's certainly easier to read for more complex actions and does make it
> easier to pass in stuff like lists. For the python directive, it also
> makes the treatment of args and kwargs passed into the python callable
> much more explicit.
> 
> The only concern I have is that it requires a bit more knowledge of how
> yaml works and is parsed. 

Yes, there are even some pitfalls, mainly with string detection:
http://en.wikipedia.org/wiki/YAML#Pitfalls_and_implementation_defects

I assume we can provide a script as part of our "SDK" (heh) that will:
1. validate the yaml file (I haven't found any simple CLI yaml validator anyway, that wouldn't start with "python -c" or "perl -e")
2. re-print what is going to happen in some pseudo syntax (for example the directives can be shown as real shell commands if possible, variables evaluated, etc) so that people can verify it's going to do what they want

Alternatively, all of this can be a part of our standard execution process and displayed as a part of the debugging info.


> For a larger example, let's look at an excerpt from rpmlint. This is an
> example of what a set of actions could look like using key=value pairs
> and not taking advantage of many yaml structures.
> 
> -----------------------------------------------------------
>     - name: download rpms from koji
>       koji: action=download envr={{ envr }}
> 
>     - name: run rpmlint on downloaded rpms
>       python: file=run_rpmlint.py workdir={{ workdir }}
>       register: rpmlint_output
> 
>     - name: report results to resultsdb
>       resultdb: results={{ rpmlint_output }}
> -----------------------------------------------------------
> 
> It's somewhat dense but for this example, it's not that difficult to
> read.
> 
> For an example with the structures mentioned above:
> 
> ------------------------------------------------------------
> Execution:
>     - name: run createrepo
>       createrepo:
>           action: create
>           dir: "{{workdir}}/somedir"
> 
>     - name: run rpmlint on downloaded rpms
>       python:
>           file: run_rpmlint.py
>           workdir: "{{ workdir }}"
>       register: rpmlint_output
> 
>     - name: report results to resultsdb
>       resultdb:
>           results: "{{ rpmlint_output }}"
> -----------------------------------------------------------
> 
> There are some changes to the way that the actions are represented but
> it's much easier for my human eyes to parse the actions since it's
> effectively limited to one input per line.
> 
> I'm kind of partial to the second form, myself. Any other thoughts?

The former one looks better, the latter one is more readable. Especially when things get complex, the latter one might be a win. I'm OK with both approaches.