[Zope-dev] Re: Mixing recipes (zc.recipe.cmmi reuse)

[Martin Aspeli]

Sidnei da Silva wrote:

> My intent is:
> 
> "Given any recipe, no matter where data is coming from (be it an egg
> in PyPI, a Subversion checkout or a tarball), I would like to be able
> to perform an operation in the 'local copy' of the data, without
> depending on the person that wrote the recipe to have allowed me to do
> so"
> 
> An example being, after a recipe that does a Subversion checkout runs,
> my custom operation kicks in and applies a patch to the local copy
> before the buildout processing continues.
> 
> I believe that this might be doable today by writing custom
> configuration, but maybe it's such a common case that could be
> simplified.
> 
> Maybe something along the lines of (note: this is all pseudo-config):
> 
> """
> [Step1]
> recipe = some.recipe.checkout
> url = svn://url-to-repo/package
> 
> [Step2]
> recipe = zc.recipe.cmmi
> source = {Step1:location}

Do ${Step1:location}

> patch = /path/to/my/patch
> 
> [zope2]
> products = {Step2:location}
> """
> 
> I believe that something like this might already work today,

It does. Again, this is "just Python". You have a dict-like variable 
'buildout' passed to your recipe's __init__(). This has keys for each 
section, which contains a dict with keys for each option. So above, you 
could address buildout['Step1']['url'], say. You can also put things 
into this dict-of-dicts. Once a recipe has been run, subsequent recipes 
will be able to see things put into the dict.

> if not it
> might be easy to make it work that way. But what I'm after is to avoid
> Step2 above by listing the patch to be applied in Step1 even if
> 'some.recipe.checkout' does not support the 'patch' option directly.

How would you avoid naming conflicts? How would you declare where that 
option comes from? I really don't think the overhead of having to 
specify a new recipe (as in your Step2 above) is very much, and it's a 
lot more explicit.

> All in all, if you tell me that the hypotetical Step2 above really
> can't be avoided and that the best option is to make
> 'some.recipe.checkout' and any other recipes out support the 'patch'
> option directly, I would be fine with that too.

I'd suggest that's the best way. Only a limited number of recipes would 
really need 'path' - those could re-use your patch recipe via 
composition if necessary, but you have a fallback of using the recipe on 
its own.

Martin


-- 
Acquisition is a jealous mistress