Use LockMode::NONE as default lock mode

[BenMorel]

As discussed in doctrine/dbal#4391, the $lockMode parameter should not be nullable anywhere; what should be used as a default is LockMode::NONE.

There was a long standing confusion in the DBAL that can be summarized to:

• in all platforms but SQL Server / SQL Anywhere, null was equivalent to LockMode::NONE;
• in SQL Server / SQL Anywhere, LockMode::NONE resulted in using WITH (NOLOCK), which changed the effective isolation level to READ UNCOMMITTED for the table; this is not the contract of LockMode::NONE, and was qualified as a bug.

This has been fixed in doctrine/dbal#4400, and now null is not a valid value anymore for lock modes.

This PR is the sequel to the above:

• $lockMode defaults to LockMode::NONE everywhere, null is not allowed anymore
• no transaction is required anymore when using LockMode::NONE, which didn't make any sense

Notes:

• the transaction requirement for LockMode::NONE was highly inconsistent anyway: the Query required one, but EntityManager::find() didn't
• there were many inconsistencies in the documented types for $lockMode as well, which did document in many places that only an int was acceptable, but did accept or even expect null at some point: 1, 2, 3

[BenMorel]

Looks like composer lock file is broken; CI can't run.

[BenMorel]

@beberlei Could you please take a look at this PR? This should be an easy pick.

[SenseException]

You need to re-target your PR to a different branch, but I'm not sure if this is supposed to be a bugfix or an improvement for a newer branch. composer.lock isn't in the versioning in 2.8.x and 2.9.x anymore and shouldn't be a problem.

[BenMorel]

@SenseException This is not a bugfix, rather an improvement. Should this go into 2.9.x? What's master currently, is it 3.x?

[SenseException]

If master is the correct target branch, then it needs a new upmerge. It might be a current blocker.

[BenMorel]

That's the point, I'm not sure if master is the correct branch; is it 3.x?

[SenseException]

@doctrine/team-orm Is there a suggestion about the target branch for this PR?

[github-actions]

There hasn't been any activity on this pull request in the past 90 days, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 7 days.
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[github-actions]

This pull request was closed due to inactivity.