'Twig_Error_Syntax' with message 'Unknown “render” filter

Question

I'm running drupal 8, composer and npm to perform gulp tasks.

When I run npm start.. my task manager: I get the following stack trace:

Fatal error: Uncaught exception 'Twig_Error_Syntax' with message 'Unknown "render" filter.' in /web/project/web/themes/emulsify/components/_patterns/04-templates/basic-page/_basic_page.twig:26
Stack trace:
#0 /web/project/web/themes/emulsify/pattern-lab/vendor/twig/twig/lib/Twig/ExpressionParser.php(481): Twig_ExpressionParser->getFilterNodeClass('render', 26)
#1 /web/project/web/themes/project_theme/pattern-lab/vendor/twig/twig/lib/Twig/ExpressionParser.php(466): Twig_ExpressionParser->parseFilterExpressionRaw(Object(Twig_Node_Expression_Name))
#2 /web/project/web/themes/project_theme/pattern-lab/vendor/twig/twig/lib/Twig/ExpressionParser.php(320): Twig_ExpressionParser->parseFilterExpression(Object(Twig_Node_Expression_Name))
#3 /web/project/web/themes/project_theme/pattern-lab/vendor/twig/twig/lib/Twig/ExpressionParser.php(212): Twig_ExpressionParser->parsePostfixExpression(Object(Twig_Node_Expression_Name))
#4 /web/project in /web/project/web/themes/project_theme/components/_patterns/04-templates/basic-page/_basic_page.twig on line 26

I've looked at installing twig-bridge / symfony twig via composer but I can't seem to get rid of the error message.

Do I just ditch using the twig filter "render"?

---

Update: 14/08/17

I've also ran into the same problem when trying to use the drupal_block function provided via Drupal 8's twig_tweak module.

Answer 1

The problem in the code above is that your Twig extension class is extending the internal Drupal Twig extension class. That breaks the Twig extensions added by Drupal core and that's why you are getting the error.

To fix this, you should make your Twig extensions extend Twigs internal Twig extension class. Your class should be defined like this:

class MyExtension extends \Twig_Extension {

After making that change, you can also remove arguments set for that class from the MODULE.services.yml

link

Answer 2

I've not seen this in the Drupal context, but working with other platforms that use Twig, I have seen similar issues occurring when an error occurs early in the platform setup process.

The typical sequence of events is like this:

• The platform starts running its bootup; loading the CMS core, etc.
• At some point early in this process, it hits an error.
• It then tries to render an error page.
• However, the error page uses a Twig template.
• The startup process has not yet loaded all the twig extensions used in the template.
• Boom, you get a twig error stating "unknown Twig function" instead of the real error message.

When I've had this before, it has proved very hard to diagnose what the actual error is.

The "correct" solution has been to modify the error page templates so that they are minimal and don't use any non-core twig functions. But if you're getting a crash early in the page load process it can be hard to actually do that.

In the first case, I resolved it by debugging the system and trapping what data was passed to the template. This showed me what the real error was. Resolving that error then stopped the twig error from occurring and allowed me to get into the system.

I don't know for sure if what you're seeing is the same kind of thing as what I was seeing, but it sounds similar so I hope this will help.