[Zope-CMF] <genericsetup:upgradeDepends>

[Rob Miller]

hi all,

i've got a GenericSetup branch called 'ra-depends-tag' with a working 
implementation of a <genericsetup:upgradeDepends> ZCML tag.  this tag can be 
used anywhere that you could use a <genericsetup:upgradeStep> tag (i.e. either 
standalone, or nested within a <genericsetup:upgradeSteps>).  in fact, 
upgradeDepends is simply a special case of upgradeStep that allows you to 
specify a set of profile import steps to be re-applied to the site, rather 
than calling a generic python handler.

here's an example of how it looks:

<genericsetup:upgradeDepends
     profile="Products.Something:default"
     source="1.0"
     destination="1.1"
     sortkey="10"
     title="Re-run 'foo' import step"
     import_steps="foo"
     purge="True"
     run_deps="False"
     />

or alternatively:

<genericsetup:upgradeSteps
     profile="Products.Something:default"
     source="1.0"
     destination="1.1"
     sortkey="10"
     />
     <genericsetup:upgradeDepends
         title="Re-run 'foo' and 'bar' import steps"
         import_steps="foo bar"
         purge="True"
         run_deps="False"
         />
     <genericsetup:upgradeStep
         title="Do something else"
         handler="Products.Something.upgrades.do_something_else"
         />
</genericsetup:upgradeSteps>

some notes:

- there is no problem nesting both upgradeStep and upgradeDepends tags within 
the same upgradeSteps tag

- the purge and run_deps attributes are optional and both default to False

- the import_steps attribute is of token type, so you can list multiple steps 
separated by whitespace and they will all be run

- the import_steps attribute is optional, if it is omitted then the entire 
profile will be reapplied

- it's not demonstrated in the examples above, but the 'checker' attribute 
(which points to a callable that can be run to determine whether or not the 
upgrade action should be performed) is supported, it functions exactly as it 
does within an upgradeStep tag

the justification for the existence of this tag should be pretty obvious.  one 
of the most frequent actions that need to be performed when upgrading to a new 
version of a product is the reapplication of whichever import steps have been 
modified since the last profile revision.  you could use the upgradeStep tag 
to point to a handler that performs this operation, but that requires 
boilerplate python code, and there's no easy way to express whether or not you 
want the dependencies to be run, or purge_old to be set, or even which steps 
should be run.  this tag resolves those issues.

please feel free to peek at the branch and provide feedback on the work.  if 
there are no objections, i'd like to merge this to the GS trunk as soon as it 
is deemed appropriate by the release manager.

thanks,

-r