From 395d1cee700b4d9addd13a3d9d9cac03deeffeac Mon Sep 17 00:00:00 2001
From: Joe Cheng <joe@rstudio.org>
Date: Wed, 20 May 2015 13:29:56 -0700
Subject: [PATCH] Ensure that callbacks fire in a FIFO order

Version bump required so Leaflet can detect this fix
---
 R/map.R                 |  3 +++
 R/utils.R               |  6 +++++-
 inst/tests/test-utils.R | 17 +++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/R/map.R b/R/map.R
index e1d4f4822..91790b8b0 100644
--- a/R/map.R
+++ b/R/map.R
@@ -23,6 +23,9 @@ Map <- R6Class(
       env[[key]] <- value
       value
     },
+    mget = function(keys) {
+      base::mget(keys, env)
+    },
     mset = function(...) {
       args <- list(...)
       if (length(args) == 0)
diff --git a/R/utils.R b/R/utils.R
index e314401e6..84fe4fcd5 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -580,7 +580,11 @@ Callbacks <- R6Class(
       })
     },
     invoke = function(..., onError=NULL) {
-      for (callback in .callbacks$values()) {
+      # Ensure that calls are invoked in the order that they were registered
+      keys <- as.character(sort(as.integer(.callbacks$keys()), decreasing = TRUE))
+      callbacks <- .callbacks$mget(keys)
+
+      for (callback in callbacks) {
         if (is.null(onError)) {
           callback(...)
         } else {
diff --git a/inst/tests/test-utils.R b/inst/tests/test-utils.R
index 391ff941b..6477dc638 100644
--- a/inst/tests/test-utils.R
+++ b/inst/tests/test-utils.R
@@ -100,3 +100,20 @@ test_that("anyUnnamed works as expected", {
   x <- x[3:4]
   expect_true(anyUnnamed(x))
 })
+
+test_that("Callbacks fire in predictable order", {
+  cb <- Callbacks$new()
+
+  x <- numeric(0)
+  cb$register(function() {
+    x <<- c(x, 1)
+  })
+  cb$register(function() {
+    x <<- c(x, 2)
+  })
+  cb$register(function() {
+    x <<- c(x, 3)
+  })
+  cb$invoke()
+  expect_equal(x, c(1, 2, 3))
+})