[drupal-devel] [feature] Enable override and extension of core module functions

[chx]

Issue status update for 
http://drupal.org/node/29428
Post a follow up: 
http://drupal.org/project/comments/add/29428

 Project:      Drupal
 Version:      cvs
 Component:    module system
 Category:     feature requests
 Priority:     normal
 Assigned to:  Anonymous
 Reported by:  nedjo
 Updated by:   chx
 Status:       patch (code needs review)
 Attachment:   http://drupal.org/files/issues/extend_0.patch (1.48 KB)

Corrected.




chx



Previous comments:
------------------------------------------------------------------------

Mon, 22 Aug 2005 22:47:09 +0000 : nedjo

Attachment: http://drupal.org/files/issues/module-extension-and-override.patch (1.38 KB)

A frequently requested functionality is the ability to override or
extend core module functions.


This small patch is an initial take on how to enable function extension
and overriding.  It takes the existing module_invoke() function and adds
tests for override and extension functions, in the forms
modulename_originalfunction_override() and
modulename_originalfunction_extension().  So, for example, an override
function for the core taxonomy_node_form() function as defined by a
module named testmodule would be called
testmodule_taxonomy_node_form_override(), and would be run instead of
taxonomy_node_form().  And testmodule_taxonomy_node_form_extension()
would be run every time taxonomy_node_form() was called, hence
"extending" it.


Of course, this approach would only be useful if we converted most - or
all! - of our current module function calls to use module_invoke()...




------------------------------------------------------------------------

Tue, 23 Aug 2005 11:35:06 +0000 : stefan nagtegaal

I'm not sure I get this..


Am I right when I think we can override (and change) any function in
drupal with this patch, which would give us the possibility to:
- override forms;
- override functions which generates the node links, so they (finally)
could be hidden instead of always displayed;
- any other advantages which i'm missing atm? (probably a lot, but
can't think of any right now, right here)


Stefan




------------------------------------------------------------------------

Wed, 24 Aug 2005 00:15:09 +0000 : drumm

-1


This will just encourage hacks and create weird bugs as the code
interactions become more complex.


The example form will be themeable when the new form API is in place.




------------------------------------------------------------------------

Wed, 24 Aug 2005 00:37:49 +0000 : nedjo

Thanks for the comments.


I'm throwing this out not because I think the solution I've suggested
is full or even sound, but to try to stimulate a better solution.


(The example I gave was random and not designed as one particularly
needing overriding or extending.)


Basically, the problem is: because we don't use PHP's class object
functionality or some substitute, we don't have a way of overriding or
extending object methods -- in Drupal, core functions -- beyond the
limited functionality explicitly exposed through hooks.  This problem
has fairly significant impacts.


Consider the taxonomy system and contributed modules.  We've seen
various approaches to enhancing taxonomy display, e.g., taxonomy_menu. 
But, because they can't (readily) add to the existing (core) taxonomy
system, they tend to bypass and replace it, e.g., by creating new urls
and displays.  So we get a variety of competing approaches, each
implementing its own limited set of functionality, often replicating
code.  As site admins, we have to choose between one or another
implementation, rather than being able to seamlessly combine them all.


Ideally, we'd to be able to add just the specific enhancement we want.


Is there another, better way to emulate object method overrides and
extension?  Or should we simply accept this limitation and work on
improving extendability through hooks and theming?




------------------------------------------------------------------------

Wed, 24 Aug 2005 07:26:07 +0000 : chx

Attachment: http://drupal.org/files/issues/extend.patch (1.42 KB)

I think this method would be a better way to extend pretty much
anything. Based on $_GET['q'] and the arguments from theme() you can
determine which theme function called you and can add anything. This
won't allow override but would allow extension. If we want override
then simply replace both hooks with one at the end and use $function()
syntax to enable references.