missing example code for hook_field_attach_validate()

Good idea -- patch welcome!

Here's a patch that adds the example code from the comment. Is this all we need?

Thanks!

When documenting a hook, the example code goes into the function body. See https://www.drupal.org/node/1354#hooks

Also, I guess the example needs a bit more work. As it is, it doesn't stand alone as an example of how to implement the hook. Maybe there is an example in contrib somewhere? .. maybe this isn't quite a Novice project ...

When documenting a hook, the example code goes into the function body

OK, I see. Makes sense.

Maybe there is an example in contrib somewhere?

drupalcontrib.org references taxonomy_access_field_attach_value() from hook_field_attach_validate() (see http://drupalcontrib.org/api/drupal/drupal!modules!field!field.api.php/f...). Is that of any use?

Um, we're looking for a function ending in _field_attach_validate(), not _field_attach_value() -- that's a different hook.

Sorry, I meant taxonomy_access_field_attach_validate().

taxonomy_access_field_attach_validate seems to be doing a lot. I'm trying to come up with a much more simple example, like adding validation for a very specific field.

So say a client wants to enforce the alt attribute on any image on article nodes. Something like the following could be done, right?

  if ($entity_type == 'node' && $entity->type == 'article') {
    if (!empty($entity->field_image)) {
      foreach ($entity->field_image as $langcode => $values) {
        foreach ($values as $delta => $value) {
          // make sure any images have an alt text
          if (!empty($value['fid']) && empty($value['alt'])) {
            $errors['field_image'][$langcode][$delta][] = array(
              'error' => 'field_example_invalid',
              'message' => t('All images in articles need to have an alternative text set.'),
            );
          }
        }
      }
    }
  }

However, I think it still looks a bit ugly, especially with those nested loops. It probably needs some more work.

Also, I noticed that in the documentation for FieldValidationException::__construct (which is where $error gets passed to), it says the array is supposed to be keyed by field name and delta. The examples I've seen also include the language code for the field. So either the documentation needs to be updated, or the examples (and the contrib module) are using the hook slightly wrong.

Should the langcode not be necessary, I'd change the example to use field_get_items instead of iterating over the entity's field_image property.

Thanks for the feedback. I made it into a patch and also moved the comment to the beginning of the function body to be more in line with the documentation of other hooks. Joining the first two if-statements also got rid of a level of indentation.

Looks great to me!

Could we fix one more thing in this hook documentation though? The doc block says "See field_attach_validate() for details and arguments." However, field_attach_validate() doesn't actually provide any useful documentation about $errors, as far as I can see. I found information about $errors on hook_field_validate(). So I think we should either link to that hook or copy its documentation about $errors (I had to look there to see whether the example code in the patch was doing the right thing with the errors or not; I think it is).

Improved the documentation for errors parameter

Would be useful to supply the patch :)

Thanks! Looks exellent to me too. Committed to 7.x.