Support Shiny async/promises based rendering

Author: jcheng5

DESCRIPTION

@@ -43,7 +43,8 @@ Imports:
     rlang,
     crosstalk,
     purrr,
-    data.table
+    data.table,
+    promises
 Suggests:
     MASS,
     maps,
@@ -52,7 +53,7 @@ Suggests:
     testthat,
     knitr,
     devtools,
-    shiny (>= 0.14),
+    shiny (>= 1.1.0),
     curl,
     rmarkdown,
     Rserve,

NEWS.md

@@ -12,6 +12,7 @@
 * The selection (i.e., linked-brushing) mode can now switch from 'transient' to 'persistent' by holding the 'shift' key. It's still possible to _force_ persistent selection by setting `persistent = TRUE` in `highlight()`, but `persistent = FALSE` (the default) is now recommended since it allows one to switch between [persistent/transient selection](https://plotly-book.cpsievert.me/linking-views-without-shiny.html#transient-versus-persistent-selection) in the browser, rather than at the command line.
 * The `highlight()` function gains a `debounce` argument for throttling the rate at which `on` events may be fired. This is mainly useful for improving user experience when `highlight(on = "plotly_hover")` and mousing over relevant markers at a rapid rate (see #1277)
 * The `animation_button()` function gains a `label` argument, making it easier to control the label of an animation button generated through the `frame` API (see #1205).
+* You can now do async rendering of Plotly plots with Shiny, using the [promises](https://rstudio.github.io/promises/) package.
 
 ## CHANGES
 

R/shiny.R

@@ -38,10 +38,19 @@ renderPlotly <- function(expr, env = parent.frame(), quoted = FALSE) {
   if (!quoted) { expr <- substitute(expr) } # force quoted
   # this makes it possible to pass a ggplot2 object to renderPlotly()
   # https://github.com/ramnathv/htmlwidgets/issues/166#issuecomment-153000306
-  expr <- as.call(list(call("::", quote("plotly"), quote("ggplotly")), expr))
+  expr <- as.call(list(call(":::", quote("plotly"), quote("prepareWidget")), expr))
   shinyRenderWidget(expr, plotlyOutput, env, quoted = TRUE)
 }
 
+# Converts a plot, OR a promise of a plot, to plotly
+prepareWidget <- function(x) {
+  if (promises::is.promising(x)) {
+    promises::then(x, ggplotly)
+  } else {
+    ggplotly(x)
+  }
+}
+
 
 #' Access plotly user input event data in shiny
 #'