@wilsonge

1) JRouterSiteTest::testParse with data set #3 ('/joomla/blog/test.json', 1, array(array('sef_suffix', null, '1')), array('', '', '', ''), array('json', 'com_test3', '45'), 'joomla/blog/test.json')
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'joomla/blog/test.json'
+'joomla/blog/test'
/home/travis/build/joomla/joomla-cms/tests/unit/suites/libraries/cms/router/JRouterSiteTest.php:252
2) JRouterSiteTest::testParse with data set #4 ('/joomla/blog/test.json/', 1, array(array('sef_suffix', null, '1')), array('', '', '', ''), array('com_test3', '45'), 'joomla/blog/test.json')
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'joomla/blog/test.json'
+'joomla/blog/test'

class plgSystemBreakit extends JPlugin {
	public function onAfterInitialise()
	{
		$router = JFactory::getApplication()->getRouter();
		$router->attachBuildRule(array($this, 'build'), PROCESS_AFTER);
		$router->attachParseRule(array($this, 'parse'), PROCESS_AFTER);
	}

	public function build($router, $uri)
	{
		if ($uri->hasVar('start')) {
			$uri->setPath($uri->getPath() . '/page-' . $uri->getVar('start'));
			$uri->delVar('start');
		}
	}

	public function parse($router, $uri)
	{
		$segments = explode('/', $uri->getPath());

		$last = end($segments);
		if (strpos($last, 'page-') === 0)
		{
			$uri->setVar('start', (int) str_replace($last, 'page-', ''));
		}
	}
}

This is just from the top of my head and not tested, but should show why the proposed code will break B/C. You don't get around deciding that behavior on a case by case basis.

The 4.0 backport is happening though after all the rules are run so that shouldn't be a problem? Otherwise in theory you've got this same issue with the plugin adding routing rules on the 4.0 branch.

The problem is not when the check is done, but that the check expects all parsed parts of the URL to be removed from the input. As you can see in my example above, that does not have to be the case.

Works here when using experimental router for articles. No effect on stable router.

I'm merging this to make the conversation on routing move beyond this stupid 404 discussion. It's easy to hit the revert button if you guys have a huge issue with me merging my own code