Forward compatibility with DBAL 4

[morozov]

This is a partial backport of #9727. The relevant changes from DBAL 4.0.x are:

1. Drop Type::getName() dbal#5208
2. Remove AbstractSchemaManager::dropAndCreate*() and ::tryMethod() methods dbal#4933
3. Drop support for PHP 7 dbal#5043
4. Get rid of hard-coded default values of maximum field lengths dbal#3586
5. Add proper types to Doctrine\DBAL\Query namespace. dbal#3574
6. Remove VersionAwarePlatformDriver and ServerInfoAwareConnection dbal#4764

[beberlei]

This will require a deprecation of setFirstResult(null). The modifyLimitQuery related changes rhis enables are nice!

[morozov]

I'd say it's a valid logical next step but not a requirement. From the standpoint of the end result, 0 and null here are and have always been identical, so this patch doesn't change anything about that.

[derrabus]

This is actually a breaking change. Symfony's test suite is now failing because Symfony's ORMQueryBuilderLoader checks if getFirstResult() returns null.

[derrabus]

Correction: The change on the QueryBuilder is actually the one that breaks Symfony's DoctrineBridge.

[morozov]

What part of the API contract does this change break?

[derrabus]

It breaks code that does not treat 0 and null as equal. One could argue though that such a piece of code has always been broken or fragile at least.

Here's the fix for Symfony: symfony/symfony#46282

[morozov]

No, I specifically mean the API contract. If passed null, the component will do this. If passed a zero, it will do that. What has changed? (Thanks for taking care of that, BTW).

Looking at the patch, I'd say you fixed an existing bug. It existed prior to the change in the ORM and now became reproducible via the existing test suite.

[derrabus]

The return value of $em->createQueryBuilder()->getFirstResult() has changed from null to 0. Do we consider this to be part of the API contract? The doc block says we do:

orm/lib/Doctrine/ORM/QueryBuilder.php

Line 651 in 07ee555

* Returns NULL if {@link setFirstResult} was not applied to this QueryBuilder.

[morozov]

In this case, it's a minor BC break. The proper documentation should have said "Returns NULL or 0..." and the clients should have checked for null or zero. Then this change wouldn't have broken anything.