EE Gotchas: Nested ‘No_results’ Tags

Last night, whilst working on a simple ExpressionEngine module, I encountered an annoying bug in the EE Template parser. Namely, ExpressionEngine fails to output no_results blocks in nested template tags.

This is a pretty pernicious bug, for two reasons:

  1. It affects all ExpressionEngine developers, not just add-on developers such as myself1;
  2. It only appears under specific circumstances.

The second point is something of a double-edged sword for the typical EE developer.

On the one hand, it means you can easily work around the issue, once you understand it (read on for the fix). On the other hand, it makes it very easy to break your site with a seemingly innocuous edit.

Show and tell

I’ve built a quick plugin to demonstrate the issue. If you want to play along at home for (purely optional) extra credits, you can grab it from GitHub.

The following example code uses the test_case method of the aforementioned plugin to automatically return the no_results content:

{exp:channel:entries channel='blog' limit='1'}
    {if no_results}<p>Nested "no results" content.</p>{/if}

Assuming the most recent entry in our blog is entitled “The Cold Hard Bluths”, we would expect to see the following:

<h2>The Cold Hard Bluths</h2>
<p>Nested "no results" content.</p>

In reality, we just get the headline.

A series of sneaks

This is where the things start to get tricky.

If the “parent” template tag has its own no_results block, everything works. So, the following code will output the nested no_results content, even though the Channel Entries no_results block is ignored:

{exp:channel:entries channel='blog' limit='1'}
  {if no_results}<p>Magic!</p>{/if}
    {if no_results}<p>Nested "no results" content.</p>{/if}
{!-- Output --}
<h2>The Cold Hard Bluths</h2>
<p>Nested "no results" content.</p>

WTF indeed, dear reader.

A simple workaround (for EE developers)

If you’re not an add-on developer, you can safely make a note of the above fix, and stop reading.

Ensure that your “parent” template tag has its own no_results block, and you’ll never fall foul of this unpleasant little bug.

A simple fix (for add-on developers)

Sadly, the above workaround isn’t much help if you are an add-on developer, as you can’t very well insist that your users employ it in every template.

Instead of the aforementioned workaround, we need a (very) slightly more sophisticated fix. Rather than relying on ExpressionEngine to locate and parse the no_results content, we’re going to do it ourselves.

A side bonus of this minor hassle is that we get to name the no_results block whatever we want. For example:

  • An affiliate management module could use {if no_affiliates};
  • A hotel bookings system could use {if no_available_rooms};
  • And so forth.

In fact, using a custom name for the no_results tag enables us to neatly sidestep any further nesting issues, and keep our code simple.

Here’s the basic fix, in all its simplistic glory:

$tagdata  = $this->EE->TMPL->tagdata;
$tag_name = 'no_soup_for_you';    
$pattern  = '#' .LD .'if ' .$tag_name .RD .'(.*?)' .LD .'/if' .RD .'#s';

if (is_string($tagdata) && is_string($tag_name)
  && preg_match($pattern, $tagdata, $matches)
  return $matches[1];

You can see it in action by adding the following code to your template:

{exp:channel:entries channel='blog' limit='1'}      
    {if no_soup_for_you}<p>Come back, one year!</p>{/if}

Which will output the following dream comedy mashup:

<h2>The Cold Hard Bluths</h2>
<p>Come back, one year!</p>

Job done.

  1. In this post, an “ExpressionEngine developer” is someone who uses pre-built ExpressionEngine add-ons to create ExpressionEngine templates; an “add-on developer” builds said add-ons. ↩︎

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