If one mistakenly specifies read preference as a symbol in Mongoid, as follows:

development:
  clients:
    default:
      database: mongoid
      hosts:
        - localhost:27100
      options:
        read: :primary

Instead of the correct specification which uses a hash with mode subkey, as follows:

development:
  clients:
    default:
      database: mongoid
      hosts:
        - localhost:27100
      options:
        read:
          mode: :primary

The driver produces an error as follows:

Mongo::Error::InvalidReadOption (Invalid read option: primary: must be a hash)

The driver can in addition suggest a fix which is to replace the primitive value (:primary) with a hash (

).

Test apps: https://github.com/p-mongo/tests/tree/master/mongoid-spec-rp-symbol & https://github.com/p-mongo/tests/tree/master/mongoid-spec-rp-hash.

Original report:

Here is a coding error. It is not related to the database, seem to be a driver only error.

My server environment works but my RSpec tests don't work.

1. See backtrace.png for the error. It's all about the mongo and mongoid gems. I tried with mongoid 6.1.1, 6.2.1 and 6.4.2. Although the error message is a bit different with 6.1.1.
2. See init.png. The initialization is correct, at least that part the :read value which is a hash.
3. Since 6.0.0, the read mode ("primary") is taken out of the hash. See read_mode.png
4. Finally, the options :read value is no longer a hash (of course, it was taken out of it in step 3). This causes the exception we see in step 3. The validate call errors out.