#REST

The issue arises when creating a URL from a request using the Url::createFromRequest($request) method.
When the Router class tries to match the url of the $request parameter to a route, we reach this code:

// Check HTTP method requirement.
if ($requiredMethods = $route->getMethods()) {
  // HEAD and GET are equivalent as per RFC.
  if ('HEAD' === $method = $this->context->getMethod()) {
    $method = 'GET';
  }

  if (!in_array($method, $requiredMethods)) {
    $this->allow = array_merge($this->allow, $requiredMethods);
    $routes->remove($name);
    continue;
  }
}

The problem is that the $method used to check against $requiredMethods is not obtained from the current $request, but from $context, which is the original request from the request stack.

This leads to an issue with REST exports that use the Facets serializer view style. When building the facets results, FacetsUrlGenerator::getUrlForRequest() wants to create a URL from a request to the actual view display(made with GET), not to the preview form(made with POST), thus resulting in a method mismatch and an exception being thrown.

I've added a patch for the Facets module to catch this exception.

I've also changed the issue project from views-ui to facets.