Trimming whitespace from Drupal form submissions using an HTTP middleware

Leading and trailing whitespaces. The bane of normalized data everywhere. It seems like a constant task that needs to be performed on incoming user data. When working with Laravel, I use the TrimStrings middleware. Calls PHP's built-in trim function on all string values for the request query and input values – including JSON! While working on my project WhiskeyDex, I noticed how mobile device keyboards always add trailing whitespace when using the autocomplete functionality. This, in turn, meant user-created data will end up with trailing whitespaces. I started to just quick-fix in the single instance and realized it should be solved once and for all.

Drupal does not provide as many developer-friendly tools as Laravel, so I needed to recreate my version of the TrimStrings middleware. It's fairly simple, requiring one class and its service registration. Note: the following code is for PHP 8.1.

In your module, create a src/StackMiddleware/TrimMiddleware.php file with the following:

<?php

declare(strict_types=1);

namespace Drupal\whiskeydex\StackMiddleware;

use Symfony\Component\HttpFoundation\InputBag;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

final class TrimMiddleware implements HttpKernelInterface {

  public function __construct(
    private readonly HttpKernelInterface $app
  ) {
  }

  public function handle(
    Request $request,
    int $type = self::MAIN_REQUEST,
    bool $catch = TRUE): Response {
    $this->trimBag($request->query);
    $this->trimBag($request->request);
    return $this->app->handle($request);
  }

  private function trimBag(InputBag $bag): void {
    $bag->replace($this->trimArray($bag->all()));
  }

  private function trimArray(array $array): array {
    return array_map(
      function ($value) {
        if (is_array($value)) {
          return $this->trimArray($value);
        }
        return is_string($value) ? trim($value) : $value;
      },
      $array
    );
  }

}

The real work is in trimArray, which iterates through the array, and any nested ones, returning trimmed strings.

Then register the service in your module’s services.yml:

services:
  http_middleware.trim:
    class: Drupal\whiskeydex\StackMiddleware\TrimMiddleware
    arguments: ['@kernel']
    tags:
      - { name: http_middleware }

Here is a link to a gist of the code as well: https://gist.github.com/mglaman/4533051f0ec50ebd698bbde93c1ac79b