Skip the empty input messages Shiny sends after deferred inputs

Shiny's input batcher checks whether a send is already queued but, since 1.7.5, never records that one is, so every deferred setInput queues its own send. The first carries all pending inputs and the rest send an empty update. The server runs a full input cycle for each: it walks every output of the session to update its hidden state, then flushes. Mounting a block card sets about a dozen inputs, so a dock view sends mostly empty messages while its cards mount, and the dock's own messages queue behind them.

Usage

shiny_input_batch_dep()

Value

An htmltools::htmlDependency.

Details

The script wraps Shiny.shinyapp.sendInput to return early on an empty object. Nothing is lost: the inputs such a send would have carried went out with the first one. Once Shiny records the queued send itself (https://github.com/rstudio/shiny/issues/4436), an empty batch is left only where an event-priority input sent the batch while its send was queued, which is rare enough that the dependency can go.

Attach it once, at the page level, like shiny_has_perf_dep().

Examples

shiny::fluidPage(shiny_input_batch_dep())
#> <div class="container-fluid"></div>