Don't define unnecessary accessors with ActiveRecord Adapter.

[nagachika]

Without DB connection, ActiveRecord doesn't define methods for columns and AttrEncrypted define attr_reader and attr_writer for the encrypted columns.
As a result, AR model with attr_encrypted column return nil for the target column if the DB connection was lost at the load time.

$ bundle exec rails console
> MyModel.create!(my_column: "deadbeef")
> MyModel.last.my_column
=> "deadbeef"
> exit
(← shutdown database server)
$ bundle exec rails console
> MyModel     # to load target model
MyModel (call MyModel.connection' to establish a connection)
(at this timing invoke database server)
> MyModel.last.my_column
nil

To suppress this behavior, don't define accessors if DB connection was active.
Introduce attribute_instance_methods_as_symbols_available? to detect connection failure with AcriveRecord Adapter.

[jturkel]

This would fix the swallowing of DB errors described in #217 which can lead to some pretty nasty issues. Let me know if there's anything I can do to help get this landed.

[nagachika]

Hi. Are there any chances this pull request to be merged? I have been using my own forked branch for a while. I'd like to refine the patch if needed. Any comments are welcome.

[saghaulor]

@nagachika thank you for proposing this fix. I think it makes sense. In fact, if we change the test suite slightly, it exposes the problem. Namely, by removing this line https://github.com/attr-encrypted/attr_encrypted/blob/master/test/active_record_test.rb#L45, a number of tests fail and expose the behavior that you describe. Ideally your PR would have a test to prove the behavior and fix it.

It should be noted that another test will fail as well and will require refactoring. https://github.com/attr-encrypted/attr_encrypted/blob/master/test/active_record_test.rb#L337
Namely, because your change rightfully fixes this bug, we can no longer use the IV accessor as it is no longer accidentally defined.

I will use your commit and fix the test suite in another PR. Again, thank you for your help.

[saghaulor]

Closed by #294