Dashboard: bslib::value_box() ignores `#| expandable: false` and shows Expand button

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• searched the issue tracker for similar issues
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Bug description

In a format: dashboard document, a cell that outputs a bslib component such as bslib::value_box() shows an "Expand" (full-screen) button in the bottom-right corner even when the cell sets #| expandable: false. A Quarto-native value box, or a plain plot(), correctly honours the option and shows no button.

Reported in discussion #14714. Root cause traced below.

Steps to reproduce

---
format: dashboard
---

## Column

```{r}
#| expandable: false
bslib::value_box(title = "x", value = 1, theme = "primary")
```

Actual behavior

The value box renders with an "Expand" button; #| expandable: false has no effect.

Root cause (against v1.9.38, SHA 6ebb5db80eb542ac76189c3d7c33ae6f654b93d2):

1. When a cell outputs raw bslib- HTML, dashboard.lua captures it into bslibRawOutputs and re-emits it "unharmed". The cell's card options are read via readOptions(el)/makeCard(...) but applied only to the remaining non-bslib content, so #| expandable: false never reaches the value box and no data-expandable attribute is emitted on it.

   • https://github.com/quarto-dev/quarto-cli/blob/6ebb5db80eb542ac76189c3d7c33ae6f654b93d2/src/resources/filters/quarto-post/dashboard.lua#L292-L304

2. In HTML post-processing, processCards handles every .card, including the bslib value box. With no data-expandable attribute present, defaultValue decides: it suppresses the button only for elements with Quarto's own class kValueboxClass ("valuebox") or a flow layout. A bslib value box uses bslib-value-box, so the check misses and the fallback returns dashboardMeta.expandable, which defaults to true, injecting Quarto's own Expand button (kExpandBtnHtml).

   • https://github.com/quarto-dev/quarto-cli/blob/6ebb5db80eb542ac76189c3d7c33ae6f654b93d2/src/format/dashboard/format-dashboard-card.ts#L82-L101
   • https://github.com/quarto-dev/quarto-cli/blob/6ebb5db80eb542ac76189c3d7c33ae6f654b93d2/src/format/dashboard/format-dashboard-shared.ts#L53

Because the button is Quarto's, passing full_screen = FALSE to bslib::value_box() does not remove it.

Expected behavior

#| expandable: false on a cell that outputs a bslib::value_box() (or any bslib card) should suppress the Expand button, matching the behaviour of Quarto-native value boxes.

Your environment

• OS: Ubuntu 24.04
• bslib: 0.11.0.9000

(Environment as reported in discussion #14714.)

Quarto check output

Quarto 1.9.38 (as reported in discussion #14714). Root cause verified against source at tag v1.9.38 and reproduces on main. Full quarto check output was not provided by the original reporter.

Start with the reproducer in the issue, then read dashboard.lua around bslibRawOutputs and format-dashboard-card.ts around processCards/defaultValue, along with format-dashboard-shared.ts. Verify the dashboard output for a bslib::value_box() cell using #| expandable: false; done means the Quarto Expand button is absent, matching a native value box.