[Fivell]

Problem

IndexAsTableExtension#build wrote its footer wrapper back into the PagePresenter it was handed:

page_presenter.instance_variable_set(:@block, wrapped)

ActiveAdmin builds one PagePresenter per index do ... end when it loads the resource, memoized in Resource::PagePresenters#page_presenters, and get_page_presenter returns that same object on every render. So each render wrapped the previous wrapper: retained closures and block call depth grew by one per request, until rendering an index raised SystemStackError (~6k renders in a long-lived process). The footer_proc && page_presenter.block guard did not stop it, because an already-wrapped block is still truthy.

Fix

Build the wrapper as before, but render against a fresh PagePresenter that shares the original options hash, leaving the stored presenter untouched. ActiveAdmin reads the presenter only through [] and #block on both 3.5 and 4.0, so rendering is unchanged.

Prepending IndexAsTable#table_for to inject the option instead was rejected: ActiveAdmin 4 has no such method — its build calls insert_tag directly — and this gem supports both majors.

Regression cover

spec/features/index_presenter_mutation_spec.rb renders the same index repeatedly and asserts PagePresenter#block is never replaced.

Before the fix it fails with the user block swapped for the lambda this gem installs:

expected #<Proc .../subscriptions.rb:18>
     got #<Proc .../index_as_table_extension.rb:13 (lambda)>

After the fix: 25 examples, 0 failures on both the default bundle (activeadmin 3.5.1) and gemfiles/activeadmin_4.0.gemfile (activeadmin 4.0.0.beta23).

No version bump here — release separately, following the existing fix/* then release/* flow.

[Copilot]

🟢 Approval recommended

The focused fix preserves rendering behavior, adds targeted regression coverage, and has no identified blocking issues.

No open issues 🎉

What changed in this PR

Prevents repeated index renders from mutating ActiveAdmin’s shared page presenter and accumulating wrappers that can cause stack overflow.

Changes:

• Renders with a fresh presenter while preserving options and footer behavior.
• Adds regression coverage for presenter block identity and repeated footer rendering.

File	Description
spec/​features/​index_presenter_mutation_spec.rb	Tests presenter stability and footer rendering across repeated requests.
lib/​activeadmin_table_footer/​index_as_table_extension.rb	Wraps the index block in a fresh presenter instead of mutating shared state.

_{Review effort: Balanced}