Add support for withCache (#1879)

Author: wch

DESCRIPTION

@@ -35,7 +35,7 @@ Imports:
     viridisLite,
     base64enc,
     htmltools (>= 0.3.6),
-    htmlwidgets (>= 1.3),
+    htmlwidgets (>= 1.5.2.9001),
     tidyr,
     hexbin,
     RColorBrewer,

R/shiny.R

@@ -55,9 +55,10 @@ renderPlotly <- function(expr, env = parent.frame(), quoted = FALSE) {
   # objects to renderPlotly() (e.g., ggplot2, promises). It also is used 
   # to inform event_data about what events have been registered
   shiny::installExprFunction(expr, "func", env, quoted)
-  expr <- quote(getFromNamespace("prepareWidget", "plotly")(func()))
-  local_env <- environment()
-  renderFunc <- shinyRenderWidget(expr, plotlyOutput, local_env, quoted)
+  expr2 <- quote(getFromNamespace("prepareWidget", "plotly")(func()))
+  renderFunc <- shinyRenderWidget(expr2, plotlyOutput, environment(), quoted,
+    cacheHint = list(label = "renderPlotly", userExpr = expr)
+  )
   # remove 'internal' plotly attributes that are known to cause false
   # positive test results in shinytest (snapshotPreprocessOutput was added 
   # in shiny 1.0.3.9002, but we require >= 1.1)