rigor-rspec

Validates RSpec let / subject declarations within each describe / context scope. It is deliberately small: the two checks it ships have the lowest false-positive risk of the proposed RSpec surface, run in pure syntactic-walk mode, and catch real bugs that rspec / rubocop-rspec don’t always surface clearly. No RSpec runtime dependency.

It ships bundled in rigortype. Activate it under plugins::

plugins:
  - rigor-rspec

What it checks

RSpec.describe "User" do
  let(:user) { :alice }
  let(:user) { :bob }            # ← warning: duplicate `let(:user)`

  let(:tags) { tags.map(&:up) }  # ← error: self-referencing let

  context "when admin" do
    let(:user) { :admin }        # ← OK: different scope
  end
end

spec/user_spec.rb:5:3: warning: duplicate `let(:user)` in this scope (first declared at line 4); the last declaration wins at runtime
spec/user_spec.rb:7:3: error:   `let(:tags)` references its own name `tags` — this will infinite-loop at runtime

1. Duplicate let / subject declarations within the same scope — warning. RSpec’s runtime lets the last declaration win, so the first is silently shadowed; the message names the line of the first declaration.
2. Self-referencing let / subject — calling the declared name from inside its own block body — error. At runtime this infinite-loops.

The walker recognises RSpec.describe … do (root), nested describe / context … do, let(:name) / let!(:name), and subject(:name) / bare subject (the implicit :subject).

Configuration

No configuration knobs. The plugin walks every file on the project’s paths: for RSpec.describe … do blocks; files with no recognised describe block are silently skipped, so it is safe to enable project-wide alongside non-spec files.

Limitations

• No let-typo detection in it bodies. Flagging a misspelled let name inside an it block needs a much heavier walker (matcher DSL, helper methods, the let scope chain) — queued.
• No mock-target validation. expect(x).to receive(:nme) against x’s methods is a separate slice.
• No shared-context resolution. include_context, shared_context, and it_behaves_like are ignored.
• Self-reference detection is intra-block only. An indirect loop (let(:user) { foo } where foo calls back to user) is not flagged.
• Constant validation (RSpec.describe SomeClass) is the engine’s job, not this plugin’s.

Related plugins

rspec-rails and shoulda-matchers matchers are mostly behavioral (they assert runtime state, not a static type), so they are out of scope here; the queued rigor-rspec-rails and rigor-shoulda-matchers plugins would emit domain-specific diagnostics for them. The README covers that boundary in detail.

Plugin internals

The scope-walker / analyzer layout, how to run the demo, the contract surfaces this plugin exercises, and the future-direction slices are in the plugin’s README. To write a plugin, see examples/ and the rigor-plugin-author skill.