[DDC-2310] Fix evaluation of NOLOCK table hint on SQL Server

[deeky666]

This PR is complementary to doctrine/orm#910.
ORM passes null to AbstractPlatform::appendLockHint() as $lockMode which should not evaluated to LockMode::NONE unless 0 is explictly given. Otherwise ORM appends WITH (NOLOCK) to all queries even though, no query lock hint is set.

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[Ocramius]

Can you change this to if (...) { return ...; } blocks?

[deeky666]

yes I will do.

[Ocramius]

@deeky666 I'd say the ORM is wrong here, since the docblock for appendLockHint requires an integer to be passed in. Probably action to be taken only on ORM?

[deeky666]

@Ocramius I don't know if action has to be taken in ORM. At least the current implementation here is wrong because null is not a valid input parameter and should not be considered as explicit NOLOCK.
The question is what to do about invalid input here? Throw exception? This is not in the DocBlock, either =/
In SQLAnywherePlatform::appendLockHint() I threw an exception for unknown lock modes, but that failes big time in ORM, too.

[Ocramius]

@deeky666 changing the docblock to allow integer|null is also acceptable and better than introducing a BC that requires changes in ORM.

Introducing the exception can be simply if ( ! is_in($lockMode)) { throw ...; }. A bit stupid, but helps identifying where the ORM is doing it wrong immediately. I wouldn't go down this path though.