[FrameworkBundle] Fix cache pool configuration with one adapter and one provider

[fancyweb]

Q	A
Branch?	4.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets	-
License	MIT
Doc PR	-

My current YAML config is:

framework:
    cache:
        pools:
            app.cache.redis:
                adapter: "cache.adapter.redis"
                provider: "%env(REDIS_URL)%/4"
                default_lifetime: 86400

I'm trying to migrate it to PHP with the new config builder system. The problem is that ->adapter('cache.adapter.redis') does not exist in the generated config class since adapter is just a shortcut in the first place. So I have to use ->adapters(['cache.adapter.redis']) but the configuration doesn't allow it.

The difference with this patch is that we allow the case where adapters is a map that contains only one item and provider is set. The result is exactly the same and it becomes compatible with the config class.

I added an extra check for DX to avoid an \ErrorException if adapters is not an array.

[fancyweb]

Failures looks related but it's working on my local and I don't see how the changes could have broken them, I'm going to need some help 😕

[ro0NL]

perhaps more easy to tell config builder about extra methods? maintaining consistency in keys while doing so.

[nicolas-grekas]

Should we split adapter and adapters entries instead? Is that possible?
Then the rule would be more clear: adapters XOR adapter+provider

[fancyweb]

CI is green, so the failures were not related I guess :-)

@nicolas-grekas Splitting the entries couldn't be considered as a bug fix isn'it? I studied the split a bit and it would be more complicated than the current patch.

Is my proposed change too risky for 4.4? I'd really like to fix this issue to get rid of the last yaml config file in my apps 😅

[nicolas-grekas]

Thank you @fancyweb.