Errors in ui function should get stack traces

R/shinyui.R

@@ -116,10 +116,13 @@ uiHttpHandler <- function(ui, uiPattern = "^/$") {
         showcaseMode <- mode
     }
     uiValue <- if (is.function(ui)) {
-      if (length(formals(ui)) > 0)
-        ui(req)
-      else
-        ui()
+      if (length(formals(ui)) > 0) {
+        # No corresponding ..stacktraceoff.., this is pure user code
+        ..stacktraceon..(ui(req))
+      } else {
+        # No corresponding ..stacktraceoff.., this is pure user code
+        ..stacktraceon..(ui())
+      }
     } else {
       ui
     }

smoketests/stacktrace3/R.out.save

@@ -0,0 +1,11 @@
+Loading required package: shiny
+Loading required package: methods
+
+Listening on http://127.0.0.1:8765
+Warning: Error in badfunc: boom
+Stack trace (innermost first):
+    41: badfunc [${PWD}/stacktrace3/app.R#4]
+    40: server [${PWD}/stacktrace3/app.R#12]
+     1: shiny::runApp [${SHINY}/R/server.R#685]
+Error in badfunc() : boom
+NULL

smoketests/stacktrace3/app.R

@@ -0,0 +1,15 @@
+library(shiny)
+
+badfunc <- function() {
+  stop("boom")
+}
+
+ui <- fluidPage(
+)
+
+server <- function(input, output, session) {
+  on.exit(stopApp())
+  badfunc()
+}
+
+shinyApp(ui, server)

smoketests/stacktrace4/R.out.save

@@ -0,0 +1,11 @@
+Loading required package: shiny
+Loading required package: methods
+
+Listening on http://127.0.0.1:8765
+Warning: Error in badfunc: boom
+Stack trace (innermost first):
+    37: badfunc [${PWD}/stacktrace4/app.R#4]
+    36: ui [${PWD}/stacktrace4/app.R#9]
+     1: shiny::runApp [${SHINY}/R/server.R#685]
+Error in badfunc() : boom
+NULL

smoketests/stacktrace4/app.R

@@ -0,0 +1,17 @@
+library(shiny)
+
+badfunc <- function() {
+  stop("boom")
+}
+
+ui <- function(req) {
+  stopApp()
+  badfunc()
+}
+
+server <- function(input, output, session) {
+  on.exit(stopApp())
+  badfunc()
+}
+
+shinyApp(ui, server)