[drupal-devel] [bug] hook_delete_confirm -- custom controls for modules during delete cycle

Thu Jul 14 16:02:56 UTC 2005

Issue status update for 
http://drupal.org/node/26649
Post a follow up: 
http://drupal.org/project/comments/add/26649

 Project:      Drupal
 Version:      cvs
 Component:    base system
 Category:     bug reports
 Priority:     normal
 Assigned to:  thehunmonkgroup
 Reported by:  thehunmonkgroup
 Updated by:   Bèr Kessels
 Status:       patch

1: you are right about the batch deletion. In fact, that will even
benefit from this, because it might be able to use this hook.
2: the fact that both Steven and I misread your patch shows that the
use of this hook needs clarification. I am not sure how the hooks at
drupaldocs are documented, but it really needs to show up there, with
details about what to returns and what to pass along. Also some
clarification about when this hook is called is important (for that
caused the confusion at #1)

Bèr Kessels

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

July 13, 2005 - 23:53 : thehunmonkgroup

Attachment: http://drupal.org/files/issues/node_module_hook_delete_confirm.patch (547 bytes)

the proposed patch creates a hook_delete_confirm, which is called from
node_delete during the
confirmation cycle.  this hook allows modules to inject custom control
structures into the deletion
process, as they don't currently have this ability.  this is needed,
for example, in the
eventrepeat.module that i'm creating, which handles repeating/recurring
events for event.module.
without a solution such as this, there is no way for the module to put
in options for different
kinds of deletions--ex. 'this occurance only', 'this and all future
occurances', 'all occurances'.
click here [1] for a screenshot of what this hook looks like in
action...

i've tested this patch and it works great, even when multiple modules
are calling
hook_delete_confirm.  i'd also be happy to write the documentation for
hook_delete_confirm if this
patch gets accepted.
[1] http://www.apartmentlines.com/hook_delete_confirm_screenshot.PNG

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

July 14, 2005 - 00:00 : thehunmonkgroup

Attachment: http://drupal.org/files/issues/hook_delete_confirm_screenshot.PNG (92.79 KB)

just a note that this patch will apply to both 4.6.x and HEAD.  marking
the version as 'cvs'.  also, attached is the screenshot i mentioned
above.

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

July 14, 2005 - 00:28 : Steven

a) New features don't get added to 4.6, this would only go into HEAD.
b) You're using the historic argument order to implode(), and leaving
out the 2nd argument, which is not allowed according to the PHP docs.
It is best to be precise: http://php.net/implode.

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

July 14, 2005 - 00:30 : Steven

Also, you don't deal with mass-deletion. This needs to be added,
otherwise things might break if your module depends on operations being
performed on deletion.

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

July 14, 2005 - 02:03 : thehunmonkgroup

Attachment: http://drupal.org/files/issues/node_module_hook_delete_confirm_2.patch (551 bytes)

>>a) New features don't get added to 4.6, this would only go into HEAD.

no problem there.  since many people are waiting for this feature, i'll
include this patch (or a patched version of node.module) so that the
functionality will be available for those that wish to begin using my
module right away in 4.6.x

>>b) You're using the historic argument order to implode(), and leaving
out the 2nd argument, which is not >>allowed according to the PHP docs.

attached patch corrects this.

>>Also, you don't deal with mass-deletion. This needs to be added,
otherwise things might break if your >>module depends on operations
being performed on deletion.

this shouldn't be necessary, as the modules have ample tools to deal w/
mass deletion themselves--as long as they can pass some kind of control
stucture into the deletion cycle (so that the module knows what kind of
delete operation it needs to perform).  i've tested the multiple delete
functionality extensively in eventrepeat.module, and it works
flawlessly with this patch in place.  my thinking in designing this
patch was add the absolute minimum to core that allows the modules some
control in the deletion process.  i think this is all that they'll need
as long as they're well written.

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

July 14, 2005 - 11:08 : Bèr Kessels

I do like the idea of this, since i ran into a similar issue for
shazamgallery and for books. 

But, steven is right when he says you should deal with batch deletion.
in node/admin you can delete a range of nodes at once. your patch will
break that. 

And furthermore, I would like to see a good piece of documentation on
how to use this. From what you have coded it seems the hook must return
an array. Why not a straing? You concenate arrays with nothin ('') which
IMHO is bad PHP. But I guess you have good reasons for returning a
string.

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

July 14, 2005 - 16:46 : thehunmonkgroup

>>But, steven is right when he says you should deal with batch deletion.
in node/admin you can delete a >>range of nodes at once. your patch will
break that.

not true.  this patch isn't involved in the actual deletion of nodes,
only with allowing modules to pass in a control structure so they have
the ability to initiate different kinds of deletes--this doesn't
interfere w/ the admin batch delete functionality at all.  admin batch
delete has it's own custom delete function, and this hook will not be
called during it.

here is a detailed use case for this patch, so that the flow can be
seen more clearly:

in eventrepeat.module, i have a need to be able to give the user a
choice to delete entire repeat sequences, or just the current node. 
this needs to be decided at time of deletion, and i want to give them
three choices:

'this occurance'
'this occurance and all future occurances' (which deletes from the date
of the selected node forward)
'all occurances' (which deletes from today's date forward)

prior to this patch, there was no way that my module could inject this
kind of control structure into the deletion process.  here's the hook i
put into eventrepeat.module to take advantage of the new feature
provided by this patch:

function eventrepeat_delete_confirm($node) {
  if (variable_get('event_nodeapi_'. $node->type, 'never') != 'never'
&&
    variable_get('eventrepeat_nodeapi_'. $node->type, 0) == 1) {

    if ($node->eventrepeat_rid) {
      $form .= form_hidden('eventrepeat_rid', $node->eventrepeat_rid);
      $options = array(
        'this' => t('This occurance only'),
  	    'future' => t('This occurance and all future occurances'),
  	    'all' => t('All occurances')
      );
      $form .= form_radios('Repeat event--delete the following:',
'eventrepeat_delete_type', 'this', $options, $description =
        t('\'This occurance and all future occurances\' will delete
repeat events from the date of the selected node forward,
         \'All occurances\' will delete repeat events from today\'s
date forward.'),
        $required = FALSE, $attributes = NULL);
    }
    return $form;
  }
}

this injects the id of the repeat sequence and the control structure i
detailed above into the delete confirmation screen (i do some checks at
the top to make sure that this data is only injected for nodes that are
in a repeat sequence).  now, when the user clicks 'Delete', the info i
injected is available as $_POST data.  since the user clicked delete,
drupal processes the deletion of the node, and eventually during that
process eventrepeat_nodeapi is called, at which point the module grabs
the info it needs from $_POST.  if, for example, the user selected 'all
occurances', the module then calls it's own custom delete function to
handle that process.  simply put, the guts of that process is grabbing
all the nids that need to be deleted, and calling node_delete for each
one (in this case i pass in the confimation setting as well to
node_delete, to automate the process).  node_delete takes care of all
the deletion dirty work for each node.  the only tricky part is making
sure that my custom delete function isn't called from
eventrepeat_nodeapi multiple times (b/c that's called multiple times in
a multiple delete)--i take care of this by unsetting the injected $_POST
data when my custom delete function is called.  works beautifully... :)

>>And furthermore, I would like to see a good piece of documentation on
how to use this. 

hopefully the above example makes usage clear, but i'd be happy to
write up more doc if needed.  

>>From what you have coded it seems the hook must return an array. Why
not a straing? 

the hook returns an html string which is the form data that will be
injected into the confirmation screen

>>You concenate arrays with nothin ('') which IMHO is bad PHP. But I
guess you have good reasons for >>returning a string.

these steps are necessary, because:

#1 module_invoke_all returns an array, and each element of the array is
an html string that i described above.  if multiple modules return form
data to be injected into the confirmation screen, this array will have
multiple elements

#2 the $extra argument in theme confirm needs to be passed in as a
string, so i implode the array.  it's best to include the 'glue'
argument in implode (according to PHP documentation), but i don't want
a seperator--i just want to turn the array into a string.  therefore i
insert an empty string as the 'glue'.