Merge pull request ramnathv#316 from ramnathv/async

Support for Shiny async

DESCRIPTION

@@ -22,7 +22,7 @@ Imports:
     yaml
 Suggests:
     knitr (>= 1.8)
-Enhances: shiny (>= 1.0.5)
+Enhances: shiny (>= 1.1)
 URL: https://github.com/ramnathv/htmlwidgets
 BugReports: https://github.com/ramnathv/htmlwidgets/issues
 RoxygenNote: 6.0.1

R/htmlwidgets.R

@@ -358,7 +358,8 @@ createWidget <- function(name,
 #'   function.
 #' @param reportSize Should the widget's container size be reported in the
 #'   shiny session's client data?
-#' @param expr An expression that generates an HTML widget
+#' @param expr An expression that generates an HTML widget (or a
+#'   \href{https://rstudio.github.io/promises/}{promise} of an HTML widget).
 #' @param env The environment in which to evaluate \code{expr}.
 #' @param quoted Is \code{expr} a quoted expression (with \code{quote()})? This
 #'   is useful if you want to save an expression in a variable.
@@ -414,9 +415,7 @@ shinyRenderWidget <- function(expr, outputFunction, env, quoted) {
   # generate a function for the expression
   func <- shiny::exprToFunction(expr, env, quoted)
 
-  # create the render function
-  renderFunc <- function() {
-    instance <- func()
+  renderWidget <- function(instance) {
     if (!is.null(instance$elementId)) {
       warning("Ignoring explicitly provided widget ID \"",
         instance$elementId, "\"; Shiny doesn't use them"
@@ -448,8 +447,19 @@ shinyRenderWidget <- function(expr, outputFunction, env, quoted) {
     toJSON(payload)
   }
 
-  # mark it with the output function so we can use it in Rmd files
-  shiny::markRenderFunction(outputFunction, renderFunc)
+  if (!is.null(asNamespace("shiny")$createRenderFunction)) {
+    shiny::createRenderFunction(
+      func,
+      function(instance, session, name, ...) {
+        renderWidget(instance)
+      },
+      outputFunction, NULL
+    )
+  } else {
+    shiny::markRenderFunction(outputFunction, function() {
+      renderWidget(func())
+    })
+  }
 }
 
 checkShinyVersion <- function(error = TRUE) {

inst/NEWS

@@ -6,6 +6,13 @@ htmlwidgets 1.3 (unreleased)
   unintended change in #306. Only the single `WIDGET.js` file should be
   copied (where `WIDGET` is the widget name). Fixed via #312.
 
+* Support for async Shiny. Widget render functions that use the default
+  implementation of `htmlwidgets::shinyRenderWidget` can receive
+  promises of widget objects (you can, of course, continue to use
+  regular widget objects as well).
+
+  See https://rstudio.github.io/promises for more about async Shiny.
+
 htmlwidgets 1.2
 -----------------------------------------------------------------------