ContextHandler.getAliasChecks() breaks Spring Boot

[sbordet]

Jetty version(s)
9.4.45

Description
In 9.4.44, ContextHandler.getAliasChecks() returned a mutable collection, and Spring Boot's JettyServletWebServerFactory was calling ContextHandler.getAliasChecks().clear() -- instead of ContextHandler.clearAliasChecks().

In 9.4.45, the collection returned by getAliasChecks() is now immutable, so clear() now throws UnsupportedOperationException.

[sbordet]

@lachlan-roberts getAliasChecks() returns an immutable collection from the work on #7059 in commit (e0beeea).

I would revert it back to a mutable collection only in 9.4.x (keep it immutable in 10.0.x+), unless there are strong reasons against.
We should also file a PR to Spring Boot to use clearAliasChecks() instead.

@joakime thoughts?

[joakime]

I agree, lets not break the API for spring-boot on Jetty 9.

[olamy]

done here spring-projects/spring-boot#29552

[gregw]

Can we add something to our pre-release checks to avoid breaking spring in future?

[olamy]

we have one once release is staged maybe a weekly/nightly build to test our snapshots against spring?

[joakime]

@gregw the pre-release checks (namely the cometd build+test) is how this was discovered.

[joakime]

The change on the spring side was merged in PR spring-projects/spring-boot#29555

[sbordet]

Fixed by #7443.