AddExpressionLanguageProvidersPass breaks custom routers

[wizhippo]

Symfony version(s) affected: 5.1

Description
Previously in 5.0 there were no services tagged with routing.expression_language_provider so the issue did not arise. There is in 5.1 so the issue can occur.

addExpressionLanguageProvider is not part of the router interface. As such AddExpressionLanguageProvidersPass should not use it if the router does not support it as the router could be replaced with a custom router that does not support the function.

symfony/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/AddExpressionLanguageProvidersPass.php

Line 34 in e60a876

$definition->addMethodCall('addExpressionLanguageProvider', [new Reference($id)]);

How to reproduce
Example ezplatform replaces the router.default with its own router which does not implement addExpressionLanguageProvider nor should it have to if it is not part of the interface.

Possible Solution
Check it router supports addExpressionLanguageProvider first.
Make addExpressionLanguageProvider part of the router interface.
Apply to router.default instead of router and stipulate route.default has to be the symfony router or extended class.

[nicolas-grekas]

Would you mind sending a PR, branch 5.1?
An is_a() check might do it, isn't it?

[wizhippo]

Personally I think the pass should target router.default instead of router. This would fix the issue I am seeing. It is router that normally would be replaced and router.default is added to the chain_router which replaces router