Schema validator doesn't report invalid indexBy configuration.

[janklan]

Bug Report

Q	A
BC Break	no
Version	Tested on 2.x and 3.x

Reproducer

https://github.com/janklan/doctrine-bug-11608. Follow the instructions in README.md to see the bug in action.

A detail of what's happening

1. In my reproducer, the Plan::$subscription collection uses custom indexBy to allow fetching a Subscription using a Customer ID when known.
2. The value of indexBy is deceiving because it matches the name of the property but not the name of the DB column
3. As a result, Doctrine fails to set the collection index, falling back to numeric indexes as if the indexBy wasn't used.

Consequence

1. Hard-to-debug errors when using Collection methods working with the keys

What's wrong

1. I expected bin/console doctrine:schema:validate to pick up on this misconfiguration

Related issues

I reckon this one is quite relevant #4203