Relation with name `:schema' causes registration problems

[dchandekstark]

Describe the bug

Non-aliased schema name :schema appears to cause relation registration problems.

To Reproduce

My relation has this configuration snippet:

schema(:schema) do
   ...
end

When I register the relation with a configuration, create a container with the config, then access the relation:

contianer.relations[:schema]

I get an error:

       16: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize.rb:88:in `load_relations'
       15: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize/finalize_relations.rb:32:in `run!'
       14: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/registry.rb:31:in `new'
       13: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/registry.rb:31:in `new'
       12: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/relation_registry.rb:11:in `initialize'
       11: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize/finalize_relations.rb:33:in `block in run!'
       10: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize/finalize_relations.rb:33:in `each'
        9: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize/finalize_relations.rb:50:in `block (2 levels) in run!'
        8: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/setup/finalize/finalize_relations.rb:108:in `build_relation'
        7: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/support/memoizable.rb:15:in `new'
        6: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/support/memoizable.rb:15:in `new'
        5: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/dry-initializer-3.0.4/lib/dry/initializer/mixin/root.rb:7:in `initialize'
        4: from (eval):18:in `__dry_initializer_initialize__'
        3: from (eval):18:in `instance_exec'
        2: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/relation.rb:154:in `block in <class:Relation>'
        1: from /Users/dc/.rvm/gems/ruby-2.6.5@solrbee/gems/rom-core-5.2.3/lib/rom/plugins/relation/registry_reader.rb:38:in `block (2 levels) in define_readers!'
NoMethodError (undefined method `[]' for nil:NilClass)

If I change the relation config to alias the name `:schema':

schema(:schema, as: :foo_schema) do
   ...
end

then

container.relations[:foo_schema]

works as expected.

Expected behavior

If :schema needs to be reserved, then registration should emit appropriate advice on failure, such as "cannot use name reserved name ':schema' in relation registry". Otherwise, registration would work as normal.

Your environment

• Affects my production application: NO
• Ruby version: 2.6.5
• OS: MacOS Catalina 10.15.7