Implement autoreload

NEWS

@@ -33,6 +33,13 @@ shiny 0.12.2.9000
 * `invalidateLater` and `reactiveTimer` no longer require an explicit `session`
   argument; the default value uses the current session.
 
+* Added `session$reload()` method, the equivalent of hitting the browser's
+  Reload button.
+
+* Added `shiny.autoreload` option, which will automatically cause browsers to
+  reload whenever Shiny app files change on disk. This is intended to shorten
+  the feedback cycle when tweaking UI code.
+
 shiny 0.12.2
 --------------------------------------------------------------------------------
 

R/app.R

@@ -179,14 +179,18 @@ shinyAppDir_serverR <- function(appDir, options=list()) {
   }
 
   oldwd <- NULL
+  monitorHandle <- NULL
   onStart <- function() {
     oldwd <<- getwd()
     setwd(appDir)
+    monitorHandle <<- initAutoReloadMonitor(appDir)
     if (file.exists(file.path.ci(appDir, "global.R")))
       sourceUTF8(file.path.ci(appDir, "global.R"))
   }
   onEnd <- function() {
     setwd(oldwd)
+    monitorHandle()
+    monitorHandle <<- NULL
   }
 
   structure(
@@ -200,6 +204,52 @@ shinyAppDir_serverR <- function(appDir, options=list()) {
   )
 }
 
+# Start a reactive observer that continually monitors dir for changes to files
+# that have the extensions: r, htm, html, js, css, png, jpg, jpeg, gif. Case is
+# ignored when checking extensions. If any changes are detected, all connected
+# Shiny sessions are reloaded.
+#
+# Use option(shiny.autoreload = TRUE) to enable this behavior. Since monitoring
+# for changes is expensive (we are polling for mtimes here, nothing fancy) this
+# feature is intended only for development.
+#
+# You can customize the file patterns Shiny will monitor by setting the
+# shiny.autoreload.pattern option. For example, to monitor only ui.R:
+# option(shiny.autoreload.pattern = glob2rx("ui.R"))
+#
+# The return value is a function that halts monitoring when called.
+initAutoReloadMonitor <- function(dir) {
+  if (!getOption("shiny.autoreload", FALSE)) {
+    return(function(){})
+  }
+
+  filePattern <- getOption("shiny.autoreload.pattern",
+    ".*\\.(r|html?|js|css|png|jpe?g|gif)$")
+
+  lastValue <- NULL
+  obs <- observe({
+    files <- sort(list.files(dir, pattern = filePattern, recursive = TRUE,
+      ignore.case = TRUE))
+    times <- file.info(files)$mtime
+    names(times) <- files
+
+    if (is.null(lastValue)) {
+      # First run
+      lastValue <<- times
+    } else if (!identical(lastValue, times)) {
+      # We've changed!
+      lastValue <<- times
+      for (session in appsByToken$values()) {
+        session$reload()
+      }
+    }
+
+    invalidateLater(getOption("shiny.autoreload.interval", 500))
+  })
+
+  obs$destroy
+}
+
 # This reads in an app dir for a single-file application (e.g. app.R), and
 # returns a shiny.appobj.
 shinyAppDir_appR <- function(fileName, appDir, options=list()) {
@@ -233,12 +283,16 @@ shinyAppDir_appR <- function(fileName, appDir, options=list()) {
   fallbackWWWDir <- system.file("www-dir", package = "shiny")
 
   oldwd <- NULL
+  monitorHandle <- NULL
   onStart <- function() {
     oldwd <<- getwd()
     setwd(appDir)
+    monitorHandle <<- initAutoReloadMonitor(appDir)
   }
   onEnd <- function() {
     setwd(oldwd)
+    monitorHandle()
+    monitorHandle <<- NULL
   }
 
   structure(

R/shiny.R

@@ -42,6 +42,22 @@ NULL
 #'   \item{shiny.trace}{If \code{TRUE}, all of the messages sent between the R
 #'     server and the web browser client will be printed on the console. This
 #'     is useful for debugging.}
+#'   \item{shiny.autoreload}{If \code{TRUE} when a Shiny app is launched, the
+#'     app directory will be continually monitored for changes to files that
+#'     have the extensions: r, htm, html, js, css, png, jpg, jpeg, gif. If any
+#'     changes are detected, all connected Shiny sessions are reloaded. This
+#'     allows for fast feedback loops when tweaking Shiny UI.
+#'
+#'     Since monitoring for changes is expensive (we simply poll for last
+#'     modified times), this feature is intended only for development.
+#'
+#'     You can customize the file patterns Shiny will monitor by setting the
+#'     shiny.autoreload.pattern option. For example, to monitor only ui.R:
+#'     \code{option(shiny.autoreload.pattern = glob2rx("ui.R"))}
+#'
+#'     The default polling interval is 500 milliseconds. You can change this
+#'     by setting e.g. \code{option(shiny.autoreload.interval = 2000)} (every
+#'     two seconds).}
 #'   \item{shiny.reactlog}{If \code{TRUE}, enable logging of reactive events,
 #'     which can be viewed later with the \code{\link{showReactLog}} function.
 #'     This incurs a substantial performance penalty and should not be used in
@@ -212,6 +228,10 @@ workerId <- local({
 #'   endpoint. The return value of \code{filterFunc} should be a Rook-style
 #'   response.
 #' }
+#' \item{reload()}{
+#'   The equivalent of hitting the browser's Reload button. Only works if the
+#'   session is actually connected.
+#' }
 #' \item{request}{
 #'   An environment that implements the Rook specification for HTTP requests.
 #'   This is the request that was used to initiate the websocket connection
@@ -693,6 +713,9 @@ ShinySession <- R6Class(
       if (private$showcase)
         self$sendCustomMessage("reactlog", logEntry)
     },
+    reload = function() {
+      self$sendCustomMessage("reload", TRUE)
+    },
 
     # Public RPC methods
     `@uploadieFinish` = function() {

inst/www/shared/shiny.js

@@ -1108,6 +1108,10 @@ var ShinyApp = function() {
     }
   });
 
+  addCustomMessageHandler('reload', function(message) {
+    window.location.reload();
+  });
+
 
   // Progress reporting ====================================================
 

man/session.Rd

@@ -76,6 +76,10 @@
   endpoint. The return value of \code{filterFunc} should be a Rook-style
   response.
 }
+\item{reload()}{
+  The equivalent of hitting the browser's Reload button. Only works if the
+  session is actually connected.
+}
 \item{request}{
   An environment that implements the Rook specification for HTTP requests.
   This is the request that was used to initiate the websocket connection

man/shiny-options.Rd

@@ -16,6 +16,22 @@ be set with (for example) \code{options(shiny.trace=TRUE)}.
   \item{shiny.trace}{If \code{TRUE}, all of the messages sent between the R
     server and the web browser client will be printed on the console. This
     is useful for debugging.}
+  \item{shiny.autoreload}{If \code{TRUE} when a Shiny app is launched, the
+    app directory will be continually monitored for changes to files that
+    have the extensions: r, htm, html, js, css, png, jpg, jpeg, gif. If any
+    changes are detected, all connected Shiny sessions are reloaded. This
+    allows for fast feedback loops when tweaking Shiny UI.
+
+Since monitoring for changes is expensive (we simply poll for last
+    modified times), this feature is intended only for development.
+
+You can customize the file patterns Shiny will monitor by setting the
+    shiny.autoreload.pattern option. For example, to monitor only ui.R:
+    \code{option(shiny.autoreload.pattern = glob2rx("ui.R"))}
+
+The default polling interval is 500 milliseconds. You can change this
+    by setting e.g. \code{option(shiny.autoreload.interval = 2000)} (every
+    two seconds).}
   \item{shiny.reactlog}{If \code{TRUE}, enable logging of reactive events,
     which can be viewed later with the \code{\link{showReactLog}} function.
     This incurs a substantial performance penalty and should not be used in

srcjs/shinyapp.js

@@ -516,6 +516,10 @@ var ShinyApp = function() {
     }
   });
 
+  addCustomMessageHandler('reload', function(message) {
+    window.location.reload();
+  });
+
 
   // Progress reporting ====================================================