Dashboard card hydration issue

[maokomioko]

Dashboard card hydration regression

Summary

Requests hitting Avo::Dashboards::CardsController#show can raise NoMethodError: undefined method hydrate' for nilafter the first dashboard render. The controller callscard.hydrateon the result ofparent.item_at_index(params[:index]), but the lookup returns nil` because card indices drift between requests.

Root cause

1. Avo::Dashboards::BaseDashboard mixes in Avo::Cards::Concerns::HasCards, which tracks a card_index counter and a cards_holder array.
2. In Avo 3.24.x the concern stores card_index as a class_attribute. The counter therefore retains its value across instances and requests.
3. Every time the DSL method card is invoked, card_index is incremented.
4. Rendering the dashboard page (first request) builds the card list and leaves the counter at the total number of items (e.g. 4).
5. Each subsequent hydration request (triggered by the dashboard fetching /cards/:id) also calls fetch_cards. Because the counter was never reset, the first card invocation in that request assigns index 4 instead of 0. As a result item_at_index(0) returns nil, leading to the crash.

Reproduction steps

1. Upgrade an app to Avo 3.24.x (the issue is tied to the class_attribute change in HasCards).
2. Define a dashboard with at least one card in def cards.
3. Load the dashboard in the browser.
4. Observe that the initial render succeeds, but XHR calls to /admin/dashboards/:dashboard/cards/:card_id fail with NoMethodError: undefined method hydrate' for nil`.

Suggested fix

Reset both the card_index class attribute and the instance @cards_holder before repopulating cards. This keeps indices aligned with the positions expected by the hydration controller.

class Avo::Dashboards::Base < Avo::Dashboards::BaseDashboard
  def fetch_cards
    self.class.card_index = 0
    @cards_holder = []

    super
  end
end

Impacted versions

• Confirmed on Avo 3.24.1 (avo-dashboards 3.24.1).
• Not reproducible on earlier releases where card_index was stored per instance.

Related production issue

• Sentry issue CORE-28: repeated hits on /admin/dashboards/client/cards/clients_payouts_upcoming_metric triggered the exception and impacted multiple users.
  https://guestit-ab-dr.sentry.io/share/issue/99b041c0209d4bef82c53a7515af966b/

[linear]

AVO-800 Dashboard card hydration issue

[Paul-Bob]

Thanks for reporting this and for all the details, @maokomioko!

[Paul-Bob]

@maokomioko I'm not able to reproduce this. I also checked the card_index code, and it hasn’t been modified in the last 2 years:

Could you please verify if there’s any monkey patch triggering the issue? Alternatively, could you create a minimal reproduction repository so I can take a closer look?

Thanks!