Deprecate locking of dirty records

[schuetzm]

lock! and with_lock reload the record before doing the actual locking. If there were any unsaved changes, they will be discarded without any warning. IMO this behaviour is dangerous and error prone.

See also #19743

[rails-bot]

r? @schneems

(@rails-bot has picked a reviewer for you, use r? to override)

[rafaelfranca]

Thank you for the pull request. What is the next step after this deprecation? When we remove the deprecation how the code will prevent this to happen again?

[schuetzm]

I'd suggest to raise an exception, because that's easy to implement.

But thinking about it, there is a way that would just prevent the record from being dirty in the first place:

MyModel.where(attr: 42).first_with_lock! do |record|
    # change record
    record.save!
end

On the other hand, this is more complicated, not as handy to use (you can't load the object, pass it to some other method, and lock it there), and might require major refactoring for the end users. So I'd still go with the exception.

[rafaelfranca]

No need to WARNING! here.

[rafaelfranca]

Locking a record with unpersisted changes is deprecated and will raise an exception in Rails 5.1. Use

[rafaelfranca]

Use Ruby 1.9 hash syntax here.

[schuetzm]

@rafaelfranca I addressed your comments.

[schuetzm]

@rafaelfranca Rebased.

[rafaelfranca]

Could you add a CHANGELOG entry?

[kamipo]

5.2?

[schuetzm]

Added a changelog entry and changed the version in the deprecation notice to 5.2.

[schuetzm]

@rafaelfranca Rebased again.

[rafaelfranca]

Sorry I forgot to ask before but can you add a test for this deprecation?

[schuetzm]

Done.