Extending the schema

Adding a custom model: Add a new class-backed type beyond DataObject
Adding a custom operation: Add a new operation for model types
Adding middleware: Add middleware to to extend query execution
The global schema: How to push modifications to every schema in the project

Adding middleware

Middleware is any piece of functionality that is interpolated into a larger process. A key feature of middleware is that it can be used with other middlewares in sequence and not have to worry about the order of execution.

In silverstripe/graphql, middleware is used for query execution, but could ostensibly be used elsewhere too if the API ever accomodates such an expansion.

The middleware API in the silverstripe/graphql module is separate from other common middleware APIs in Silverstripe CMS, such as HTTPMiddleware. The two are not interchangable.

The signature for middleware (defined in QueryMiddleware) looks like this:

use GraphQL\Type\Schema;

public abstract function process(Schema $schema, string $query, array $context, array $vars, callable $next);

The return value should be ExecutionResult or an array.

$schema: The underlying Schema object. Useful to inspect whether types are defined in a schema.
$query: The raw query string.
$context: An arbitrary array which holds information shared between resolvers. Use implementors of ContextProvider to get and set data, rather than relying on the array keys directly.
$vars: An array of (optional) Query Variables.
$next: A callable referring to the next middleware in the chain

Let's write a simple middleware that logs our queries as they come in.

namespace App\GraphQL\Middleware;

use GraphQL\Type\Schema;
use SilverStripe\GraphQL\Middleware\QueryMiddleware;
use SilverStripe\GraphQL\QueryHandler\UserContextProvider;
// ...

class LoggingMiddleware implements QueryMiddleware
{
    public function process(Schema $schema, string $query, array $context, array $vars, callable $next)
    {
        $member = UserContextProvider::get($context);

        Injector::inst()->get(LoggerInterface::class)
            ->info(sprintf(
                'Query executed: %s by %s',
                $query,
                $member ? $member->Title : '<anonymous>';
            ));

        // Hand off execution to the next middleware
        return $next($schema, $query, $context, $vars);
    }
}

Now we can register the middleware with our query handler:

SilverStripe\Core\Injector\Injector:
  SilverStripe\GraphQL\QueryHandler\QueryHandlerInterface.default:
    class: SilverStripe\GraphQL\QueryHandler\QueryHandler
    properties:
      Middlewares:
        logging: '%$App\GraphQL\Middleware\LoggingMiddleware'

Edit on Github

Extending the schema#

Adding middleware#

Extending the schema

Adding middleware