shiny-for-r

name	shiny-for-r
description	Building, styling, testing, debugging, or observing a Shiny for R app - library(shiny), shinyApp(), runApp(). Index skill: read this, then open the linked reference for the task. Covers reactivity (reactive/observe/req/isolate/bindEvent); modules; async promises and ExtendedTask; bslib layouts, navigation, cards, value boxes, and theming (incl. thematic and brand.yml); dynamic UI; plots with click/brush interaction; tables, file upload/download; notifications, modals, progress, validation; bookmarking; custom JS components; testServer testing; debugging; OpenTelemetry; and when to reach for DT, plotly, leaflet, shinychat, or shinytest2. Use when writing or changing any Shiny for R app, especially a dashboard, or when tempted to hand-roll what the framework provides - custom HTML tables, fake tabs, polling loops, blocking reactive work, or print-debugging server state.
license	MIT
metadata	{"author":"Posit Software, PBC","version":"1.0"}

Shiny for R

A Shiny app has a ui object (or function), a server(input, output, session) function, and shinyApp(ui, server) to run them together. The reactive graph is the engine: reading a reactive source (input$x, a reactive(), a reactiveVal()) inside a reactive context registers a dependency, so changing that source re-runs everything that read it — you never call outputs or schedule updates yourself.

This skill is an index. Find your task below and read the linked reference file before writing code for that area. Read the one or two references your task actually touches, not all of them.

Not every corner of Shiny has a reference here — plain inputs (selectInput(), actionButton(), ...), deployment, and app performance tuning are not covered. For those, work from your own knowledge of the package and its help pages.

Foundations

Topic	Use when	Reference
Reactivity	A value should recompute or an output update as inputs change; choosing between reactive()/observe()/observeEvent(); req(), isolate(), bindEvent(), timers, polling	references/reactivity.md
Modules	A reusable, repeatable UI+server component; avoiding input/output id collisions across copies	references/modules.md
Session lifecycle	Per-session cleanup (onSessionEnded()), flush hooks, unhandled errors, per-session vs app-level scope, session$userData	references/session-lifecycle.md

Async

Topic	Use when	Reference
Async	Returning a promises::promise from a render/observer so R keeps serving other sessions during slow I/O	references/async.md
Extended tasks	Running slow work in a background process while the session that started it stays fully interactive; task buttons	references/extended-tasks.md

Dashboard building

Topic	Use when	Reference
Dashboard design	Turning a dataset or brief into a polished analytical dashboard; information hierarchy, shared filters, responsive layout, empty states, final visual/functional pass	references/dashboard-design.md
Dashboard components	Composing bslib card(), value_box(), accordion(), tooltip()/popover() instead of hand-rolled div() markup	references/dashboard-components.md
Layouts	Arranging a page with bslib page_sidebar(), layout_columns(), card() instead of nested fluidRow()/column() pyramids	references/layouts.md

Navigation & dynamic UI

Topic	Use when	Reference
Navigation	Grouping switchable content into a real tab container/navbar instead of faking tabs with buttons plus conditionalPanel()	references/navigation.md
Dynamic UI	UI that must change after render — update*Input(), conditionalPanel(), renderUI()/uiOutput(), or insertUI()/removeUI()	references/dynamic-ui.md

Outputs

Topic	Use when	Reference
Plots	Pairing renderPlot()/plotOutput() for base/lattice/ggplot2 graphics; click/hover/brush interaction via nearPoints()/brushedPoints()	references/plots.md
Tables	Choosing renderTable() (static), the deprecated renderDataTable(), or DT/reactable for sortable/searchable interactive tables	references/tables.md
Files	fileInput() uploads and downloadHandler()/downloadButton() generated-file downloads	references/files.md

Feedback & state

Topic	Use when	Reference
Feedback	Toasts/notifications, modal dialogs, progress bars, and input validation sent from the server, typically inside observeEvent()	references/feedback.md
Bookmarking	Saving/restoring app state via a shareable URL instead of a hand-built query string or custom persistence layer	references/bookmarking.md

Theming, assets & extending

Topic	Use when	Reference
Theming & assets	Setting bslib::bs_theme() Sass variables, thematic for plot theming, brand.yml, or adding custom CSS/JS/image assets	references/theming-assets.md
Custom components	Integrating a third-party JS widget or bespoke interaction when no built-in input/output covers it	references/custom-components.md

Testing & observability

Topic	Use when	Reference
Testing	Verifying server-side reactive logic with testServer() without starting a real Shiny process or browser	references/testing.md
Debugging	Dropping into a real R debugger (browser(), error breakpoints) instead of print()-debugging a running reactive graph	references/debugging.md
OpenTelemetry	Tracing sessions, flush cycles, and reactive/observer/output executions instead of log-scraping or ad hoc timing	references/opentelemetry.md
Ecosystem	Deciding whether a companion package (DT, plotly, leaflet, shinychat, shinytest2, etc.) already solves the problem before hand-rolling it	references/ecosystem.md