Skip the empty input messages Shiny sends after deferred inputs - #73
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christophsax wants to merge 2 commits into
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christophsax wants to merge 2 commits into
christophsax wants to merge 2 commits into
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Shiny 1.14.0's InputBatchSender checks sendIsEnqueued but never sets it, so every deferred setInput queues its own send. The first carries all pending inputs, the rest send an empty update, and the server runs a full input cycle for each (manageHiddenOutputs over every output, then a flush). On a first visit to a 15-block dock view that was 177 of 218 messages, and the dock's initialized report waited 2 to 4 s behind them. shiny_input_batch_dep() wraps Shiny.shinyapp.sendInput to return early on an empty object. The inputs such a send would carry already went out with the first one.
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The helper's skip_if_not_installed() runs outside test_that(), where lintr does not see testthat, so it is called as testthat::. The coverage test learns that shiny-input-batch.js is tested in R.
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Works around rstudio/shiny#4436.
Shiny's input batcher checks whether a send is already queued but never records that one is, so every deferred
setInput()queues its own send. The first carries all pending inputs and the rest go out as{}. The server runs a full input cycle for each empty message:manageHiddenOutputs()over every output of the session, then a flush.A dock board hits this hard. Mounting a block card sets about a dozen inputs, so a first visit to a 15-block view sent 267 messages, 174 of them empty, and the dock's
initializedreport waited 2 to 4 s behind them before anything on the view evaluated. With this dependency on the page the same visit sends 48 messages. Measured on a demo board with about 90 blocks; details are in the commit message.shiny_input_batch_dep()wrapsShiny.shinyapp.sendInputto return early on an empty object. Nothing is lost, since the inputs such a send would carry already went out with the first one. Once Shiny fixes the batcher, no empty send reaches the wrapper and the dependency can go.Attaching it is a one-line change in blockr.dock's page (
blockr_app_ui.dock_board()), which follows once this is merged. The other dock speed fixes are in BristolMyersSquibb/blockr.dock#503.Adds V8 to Suggests for the test, which runs the script against a stub of
Shiny.shinyapp.