feat: Add reload helper functions

R/app.R

@@ -55,6 +55,41 @@ as_top_level <- function(shiny_module) {
   wrap(shiny_module)
 }
 
+load_app <- function() {
+  # Silence "no visible binding" notes raised by `box::use()` on R CMD check.
+  app <- NULL
+  main <- NULL
+
+  app_env <- new.env(parent = baseenv())
+  load_main <- function() {
+    box::purge_cache()
+    local(box::use(app/main), app_env)
+  }
+
+  load_main()
+  register_reload_callback(load_main)
+
+  app_env
+}
+
+clear_reload_callback <- function() NULL
+
+register_reload_callback <- function(callback) {
+  message("@ Clearing reload callback")
+  clear_reload_callback()
+
+  message("@ Registering reload callback")
+  clear_reload_callback <<- shiny:::autoReloadCallbacks$register(
+    function() {
+      message("@ Reload callback")
+      tryCatch(
+        callback(),
+        error = function(cond) message(conditionMessage(cond))
+      )
+    }
+  )
+}
+
 with_head_tags <- function(ui) {
   wrap <- function(tag) {
     shiny::tagList(