Support class Foo < Data.define(:a, :b) as a documented superclass

[svyatov]

Description

class Foo < Data.define(:a, :b) currently registers with no superclass. The parser logs [warn]: in YARD::Handlers::Ruby::ClassHandler: Undocumentable superclass (class was added without superclass), and the rendered docs claim the class inherits Object. #1533 reports this exact case. #1600 added the constant form Foo = Data.define(:a, :b) and invited this change:

Note: the support of the class Foo < Data.define(:a, :b) form was not added by intention because I don't want to encourage this style of programming and it does not appear in the Data documentation. If one has a strong opinion that this style must be supported, they're free to do it in a separate PR.

Here is that separate PR. The strong opinion: current tooling forces the inheritance form on some projects, whatever style one prefers.

• ruby-lsp reads .rb and never sig/, so hover docs on members need a documented reader per member: def a = super. That reader works only in the inheritance form. In the block form, Data.define(:a) do def a = super end raises NoMethodError: super: no superclass method 'a' at runtime, because the block runs on the same class that defines the reader.
• Steep type-checks only the inheritance form. In the block form it attributes the methods to ::Object (do block inside class with in Data.define not correctly identified soutaro/steep#963), and the rbs guide docs/data_and_struct.md records the same preference for inheriting.
• The Data documentation not showing the form also holds for class Foo < Struct.new(...), which YARD has long supported.

Changes:

• ClassHandler#parse_superclass resolves Data.define(...) to Data, next to the existing Struct.new branch. The warning is gone and the ancestry renders correctly.
• Members become read-only attributes through the path the constant form already uses. The loop from ConstantHandler#process_dataclass moved to StructHandlerMethods#create_readers, and both handlers call it.
• The legacy parser resolves the superclass through one added regex alternative. Member specs are gated to the Ripper parser, as Support A = Data.define(:a, :b, :c) #1600's specs are.

Verified against a real tree: a gem that generates 361 such classes from the Telegram Bot API spec. Before: 361 warnings. After: zero warnings, every class renders Data ancestry with read-only member attributes, and explicitly documented readers in class bodies keep their own docstrings.

Completed Tasks

• I have read the Contributing Guide.
• The pull request is complete (implemented / written).
• Git commits have been cleaned up (squash WIP / revert commits).
• I wrote tests and ran bundle exec rake locally (if code is attached to PR).