class RSpec::Core::LegacyExampleGroupHash

@private Together with the example group metadata hash default block, provides backwards compatibility for the old ‘:example_group` key. In RSpec 2.x, the computed keys of a group’s metadata were exposed from a nested subhash keyed by ‘[:example_group]`, and then the parent group’s metadata was exposed by sub-subhash keyed by ‘[:example_group]`.

In RSpec 3, we reorganized this to that the computed keys are exposed directly of the group metadata hash (no nesting), and ‘:parent_example_group` returns the parent group’s metadata.

Maintaining backwards compatibility was difficult: we wanted ‘:example_group` to return an object that:

* Exposes the top-level metadata keys that used to be nested
  under `:example_group`.
* Supports mutation (rspec-rails, for example, assigns
  `metadata[:example_group][:described_class]` when you use
  anonymous controller specs) such that changes are written
  back to the top-level metadata hash.
* Exposes the parent group metadata as
  `[:example_group][:example_group]`.

# File rspec-core/lib/rspec/core/metadata.rb, line 473
def initialize(metadata)
  @metadata = metadata
  parent_group_metadata = metadata.fetch(:parent_example_group) { {} }[:example_group]
  self[:example_group] = parent_group_metadata if parent_group_metadata
end

# File rspec-core/lib/rspec/core/metadata.rb, line 479
def to_h
  super.merge(@metadata)
end