[development] How to implement hook_nodeapi when op is 'view'?

[Dave Cohen]

In a recent thread I asked about using #pre_render callbacks to affect the way 
nodes are rendered.  (See http://drupal.org/node/147662).  This goes some way 
toward solving my problem, but things could be better.  When my #pre_render 
hook is called, the data structure is filled with arrays that look like:

[SOME KEY HERE] => Array (
    [#value] => SOME HTML HERE
    [#weight] => SOME NUMBER HERE
)

Because the #value field contains HTML, its very hard to modify.  Practically 
speaking, all I can do is remove some fields from the node content, or 
reorder fields.  I can't manipulate each field the way I really want.  (For 
example, I may want to theme a CCK field differently depending on whether the 
node in question is a page or a story.)

I'd like to see developers stop using this #value => HTML model when 
implementing hook_nodeapi($op = 'view').  Everyone does, because the 
documentation on api.drupal.org suggests implementing it this way:

<code>
case 'view': 
       $node->content['my_additional_field'] = array( 
         '#value' => theme('mymodule_my_additional_field', $additional_field), 
         '#weight' => 10, 
       ); 
       break;
</code>

Instead, it should be implemented something like:
<code>
case 'view': 
    // my_additional_data is an array
    $node->content['my_additional_data'] = $node->my_additional_data;
    $node->content['my_additional_data']['#theme'] 
= 'mymodule_my_additional_data';
    $node->content['my_additional_data']['#weight'] = 10;
     break;
</code>

What this does is postpone the theming until drupal_render is called.  And 
#pre_render hooks have a chance to manipulate data or change the theme 
function to be called.

Please let me know if I'm right or wrong about this,

-Dave