[VarExporter] Improve error message for Lazy Ghosts failing reinitializing classes due to readonly properties

[curry684]

Q	A
Branch?	7.1
Bug fix?	sort of
New feature?	no
Deprecations?	no
Issues	#54228
License	MIT

As discussed in #54228, Lazy Ghosts cannot reinitialize classes with readonly properties due to PHP limitations. Currently, this will often lead to a vague crash minutes or even hours later stating only:

Cannot modify readonly property Doctrine\ORM\EntityManager::$conn

This PR improves the error message to:

Lazy ghost cannot reinitialize readonly property "Doctrine\ORM\EntityManager::$conn", remove the readonly modifier on that property and/or its containing class, or ensure the ghost will never be reinitialized

[carsonbot]

Hey!

Thanks for your PR. You are targeting branch "7.2" but it seems your PR description refers to branch "7.1".
Could you update the PR description or change target branch? This helps core maintainers a lot.

Cheers!

Carsonbot

[nicolas-grekas]

Testeable ?

[curry684]

Testeable ?

Would boil down to a convoluted test case just for a stringwise comparison on the error message. Not worth it imo since it can't break anything.

[derrabus]

Testeable ?

Would boil down to a convoluted test case just for a stringwise comparison on the error message. Not worth it imo since it can't break anything.

Definitely worth it because we're parsing an error message emitted by the PHP runtime and the PHP folks are infamous for applying subtle changes to their error messages in minor releases.

[curry684]

the PHP folks are infamous for applying subtle changes to their error messages in minor releases

But why... 🤦 I'll see if I can whip something up.

[curry684]

Couldn't quickly build a reliable unit test in a reasonable time, far too busy to really try for just an error message.