I hope this does not break the i18n routing bundle tests contrary to before (see #6814 and https://travis-ci.org/schmittjoh/JMSI18nRoutingBundle/jobs/3229075).
This time only query params are added that are not equal to the default value. I think this is consistent with the optional path placeholders which are also only added if different from default.

Thank you @Tobion.

This is a BC break, I'm afraid. If you had not removed lines 296 and 297 of the UrlGeneratorTest class, you would have noticed. These are the former assertions:

public function testQueryParamSameAsDefault()
{
    $routes = $this->getRoutes('test', new Route('/test', array('default' => 'value')));

    $this->assertSame('/app.php/test', $this->getGenerator($routes)->generate('test', array('default' => 'foo')));
    $this->assertSame('/app.php/test', $this->getGenerator($routes)->generate('test', array('default' => 'value')));

We have relied on the first assertion being true in Contao, which is now no longer the case.

What is your use-case for this behavior?

Our use case is pretty much what is in the first deleted assertion. We want the router to ignore the _locale request attribute if there is a default _locale route attribute. It worked like a charm up to Symfony 3.0.4 and it does no longer in Symfony 3.0.5, because now the ?_locale=xx query string is appended.

But actually the use-case should not matter. The changes affect the API in an incompatible way, which the deleted assertions would have shown if not removed. :)

Also, I'm not implying that ignoring the _locale request attribute if there is a default _locale route attribute is the right way to solve the problem. It might be not and we are currently developing a replacement solution.

Still the router now behaves differently than in Symfony 3.0.4.