Bare Templates: Removing Unnecessary Markup in Twig files

In most of the projects we build, the HTML markup provided by core just gets in the way. There is way too many wrapper divs. This can cause issues when trying to create lean markup that matches what is produced in a generated styleguide.

In this post, I'll introduce you to the concept of bare templates, and how you can remove unnecessary markup from your Twig templates.

by
Pasan Gamage
/ 15 March 2018

In Drupal 8, a couple of themes are shipped by default to serve a common set of end user needs.

Among them are:

  • Bartik: A flexible, recolourable theme with many regions and a responsive, mobile-first layout.
  • Seven: The default administration theme for Drupal 8 was designed with clean lines, simple blocks, and sans-serif font to emphasise the tools and tasks at hand.
  • Stark: An intentionally plain theme with almost no styling to demonstrate default Drupal’s HTML and CSS.
  • Stable: A base theme. Stable theme aggregates all of the CSS from Drupal core into a single theme. Theme markup and CSS will not change so any sub-theme of Stable will know that updates will not cause it to break.
  • Classy: A sub-theme of Stable. Theme designed with lot of markups for beginner themers.

But in an actual business scenario the requirements and expectations of a client towards the look and feel of the website is far more distinct than the themes that are provided in Drupal core.

When building your site based upon one of these themes it is common to face issues with templating during the frontend implementation phase. Quite often the default suggested templates for blocks, nodes, fields etc. contain HTML wrapper divs that your style guide doesn’t require.

Usually the most effective way is to build themes using the Stable theme. In Stable, the theme markup and CSS are fixed between any new Drupal core releases making any sub-theme to less likely to break on a Drupal core update. It also uses the verbose field template support for debugging.

Which leads us to use bare templates.

What is a bare template?

A bare template is a twig file that has the minimum number of HTML wrappers around actual content. It could be simple as a file with a single content output like {{content.name}}

Compared to th traditional approach, bare templates provide benefits such as:

  • Ease of maintenance: With minimum markup the complexity of the template is much lesser making it easy to maintain.
  • Cleaner Markup: The markup will only have the essential or relevant elements where as in traditional approach there are a lot of wrappers leading to a complex output.
  • Smaller page size: Less markup means less page size.
  • Avoids the need for markup removal modules: With bare markup method we do not need to use modules like fences or display suite. Which means less modules to maintain and less configuration to worry about.

Our Example

We need to create a bare template for type field and suggest it to render only field name and field_image of my_vocabulary taxonomy entity. This will avoid Drupal from suggesting this bare template for other fields belonging to different entities.

Field template

Let's have a look at field template which resides at app/core/themes/stable/templates/field/field.html.twig

{% if label_hidden %}
{% if multiple %}

{% for item in items %}
{{ item.content }}
{% endfor %}

{% else %}
{% for item in items %}
{{ item.content }}
{% endfor %}
{% endif %}
{% else %}

{{ label }}
{% if multiple %}

{% endif %}
{% for item in items %}
{{ item.content }}
{% endfor %}
{% if multiple %}

{% endif %}

{% endif %}

As you see there is quite a lot of div wrappers used in the default template which makes it difficult to style components. If you are looking for simple output, this code is overkill. There is however, a lot of valuable information is provided in the comments of field.html.twig which we can use.

{#
/**
* @file
* Theme override for a field.
*
* To override output, copy the "field.html.twig" from the templates directory
* to your theme's directory and customize it, just like customizing other
* Drupal templates such as page.html.twig or node.html.twig.
*
* Instead of overriding the theming for all fields, you can also just override
* theming for a subset of fields using
* @link themeable Theme hook suggestions. @endlink For example,
* here are some theme hook suggestions that can be used for a field_foo field
* on an article node type:
* - field--node--field-foo--article.html.twig
* - field--node--field-foo.html.twig
* - field--node--article.html.twig
* - field--field-foo.html.twig
* - field--text-with-summary.html.twig
* - field.html.twig
*
* Available variables:
* - attributes: HTML attributes for the containing element.
* - label_hidden: Whether to show the field label or not.
* - title_attributes: HTML attributes for the title.
* - label: The label for the field.
* - multiple: TRUE if a field can contain multiple items.
* - items: List of all the field items. Each item contains:
* - attributes: List of HTML attributes for each item.
* - content: The field item's content.
* - entity_type: The entity type to which the field belongs.
* - field_name: The name of the field.
* - field_type: The type of the field.
* - label_display: The display settings for the label.
*
* @see template_preprocess_field()
*/
#}
The code
Building the hook.

We will be using hook_theme_suggestions_HOOK_alter() to suggest the two fields to use our bare template when rendering.

It is important to note that only these two fields will be using the bare template and the other fields (if any) in that entity will use the default field.html.twig template to render.

my_custom_theme_theme_suggestions_field_alter (&$hooks, $vars){

    // Get the element names passed on when a page is rendered.
    $name = $vars['element']['#field_name'];

    // Build the string layout for the fields.
    // :::

    $bare_hooks = [
        'taxonomy_term:my_vocabulary:teaser:name',
        'taxonomy_term:my_vocabulary:teaser:field_logo',
    ];

    // Build the actual var structure from second parameter
    $hook = implode(':', [
        $vars['element']['#entity_type'],
        $vars['element']['#bundle'],
        $vars['element']['#view_mode'],
        $vars['element']['#field_name'],
    ]);

    // Check if the strings match and assign the bare template.
    if (in_array($hook, $bare_hooks, TRUE)) {
        $hooks[] = 'field__no_markup';
    }
}

The hook key field__no_markup mentioned in the code corresponds to a twig file which must reside under app/themes/custom/my_theme/templates/field/field--no-markup.html.twig

Debugging Output

In order to see how this is working, we can fire up PHPStorm and walk the code in the debugger.

As you can see in the output below, the implode() creates the actual var structure from the second parameter. We will use this to compare with the $bare_hooks array we created  fields specific to content entity types that we need to assign the bare template.

Note: As best practise make sure you pass a third argument TRUE to in_array(). Which will validate the data type as well.

 

Bare Template Markup

The following is the contents of our bare template file. Notice the lack of any HTML?

{#
/**
* @file
* Theme override to remove all field markup.
*/
#}

{% spaceless %}
{% for item in items %}
{{ item.content }}
{% endfor %}
{% endspaceless %}


Bare templating can be used for other commonly used templates as well. To make it render a minimal amount of elements.

Conclusion

We can always use custom templating to avoid getting into complicated markups. And have the flexibility to maintain the templates to render for specific entities.

Resources

Tagged

Style Guides, Twig

Original Article: