Errors in observeEvent have too much stack trace hidden

[jcheng5]

System details

Browser Version:

Output of `sessionInfo()`: NA

─ Session info ──────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.3.2 (2023-10-31)
 os       macOS 15.1.1
 system   aarch64, darwin20
 ui       RStudio
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       America/Los_Angeles
 date     2024-12-09
 rstudio  2024.04.2+764 Chocolate Cosmos (desktop)
 pandoc   2.19.2 @ /opt/homebrew/bin/pandoc

─ Packages ──────────────────────────────────────────────────────────────────────────────────────
 package     * version    date (UTC) lib source
 bslib         0.8.0      2024-07-29 [1] CRAN (R 4.3.3)
 cachem        1.1.0      2024-05-16 [1] CRAN (R 4.3.3)
 cli           3.6.3      2024-06-21 [1] CRAN (R 4.3.3)
 crayon        1.5.3      2024-06-20 [1] CRAN (R 4.3.3)
 devtools      2.4.5      2022-10-11 [1] CRAN (R 4.3.0)
 digest        0.6.37     2024-08-19 [1] CRAN (R 4.3.3)
 ellipsis      0.3.2      2021-04-29 [1] CRAN (R 4.3.0)
 fastmap       1.2.0      2024-05-15 [1] CRAN (R 4.3.3)
 fs            1.6.5      2024-10-30 [1] CRAN (R 4.3.3)
 glue          1.8.0      2024-09-30 [1] CRAN (R 4.3.3)
 htmltools     0.5.8.9000 2024-07-19 [1] Github (rstudio/htmltools@487aa0b)
 htmlwidgets   1.6.4      2023-12-06 [1] CRAN (R 4.3.1)
 httpuv        1.6.15     2024-03-26 [1] CRAN (R 4.3.1)
 jquerylib     0.1.4      2021-04-26 [1] CRAN (R 4.3.0)
 jsonlite      1.8.9      2024-09-20 [1] CRAN (R 4.3.3)
 later         1.4.1      2024-11-27 [1] CRAN (R 4.3.3)
 lifecycle     1.0.4      2023-11-07 [1] CRAN (R 4.3.1)
 magrittr      2.0.3      2022-03-30 [1] CRAN (R 4.3.0)
 memoise       2.0.1      2021-11-26 [1] CRAN (R 4.3.0)
 mime          0.12       2021-09-28 [1] CRAN (R 4.3.0)
 miniUI        0.1.1.1    2018-05-18 [1] CRAN (R 4.3.0)
 pkgbuild      1.4.4      2024-03-17 [1] CRAN (R 4.3.1)
 pkgload       1.4.0      2024-06-28 [1] CRAN (R 4.3.3)
 profvis       0.4.0      2024-09-20 [1] CRAN (R 4.3.3)
 promises      1.3.2      2024-11-28 [1] CRAN (R 4.3.3)
 purrr         1.0.2      2023-08-10 [1] CRAN (R 4.3.0)
 R6            2.5.1      2021-08-19 [1] CRAN (R 4.3.0)
 Rcpp          1.0.13-1   2024-11-02 [1] CRAN (R 4.3.3)
 remotes       2.5.0.9000 2024-04-03 [1] Github (r-lib/remotes@5b7eb08)
 rlang         1.1.4      2024-06-04 [1] CRAN (R 4.3.3)
 rsconnect     1.3.1      2024-06-04 [1] CRAN (R 4.3.3)
 rstudioapi    0.17.0     2024-10-16 [1] CRAN (R 4.3.3)
 sass          0.4.9.9000 2024-07-19 [1] Github (rstudio/sass@9228fcf)
 sessioninfo   1.2.2      2021-12-06 [1] CRAN (R 4.3.0)
 shiny       * 1.9.1.9000 2024-12-10 [1] local
 urlchecker    1.0.1      2021-11-30 [1] CRAN (R 4.3.0)
 usethis       3.0.0      2024-07-29 [1] CRAN (R 4.3.3)
 vctrs         0.6.5      2023-12-01 [1] CRAN (R 4.3.1)
 xtable        1.8-4      2019-04-21 [1] CRAN (R 4.3.0)

 [1] /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/library

Example application or steps to reproduce the problem

library(shiny)

ui <- fluidPage()

server <- function(input, output, session) {
  observeEvent(TRUE, {
    stop("boom")
  })
}

shinyApp(ui, server)

Describe the problem in detail

When run, this app immediately errors (as intended). The console looks like this:

Listening on http://127.0.0.1:7821
Warning: Error in observe: boom
  4: runApp [/Users/jcheng/Development/rstudio/shiny3/R/runapp.R#388]
  3: print.shiny.appobj [/Users/jcheng/Development/rstudio/shiny3/R/shinyapp.R#565]
  1: source

Note that no useful information is present about where the error is coming from. If you change observeEvent(TRUE, { to observe({, then the useful information appears (the line starting with 52:):

Listening on http://127.0.0.1:7821
Warning: Error in observe: boom
  53: stop
  52: observe [~/.active-rstudio-document#7]
  51: <observer> [/Users/jcheng/Development/rstudio/shiny3/R/utils.R#1459]
   4: runApp [/Users/jcheng/Development/rstudio/shiny3/R/runapp.R#388]
   3: print.shiny.appobj [/Users/jcheng/Development/rstudio/shiny3/R/shinyapp.R#565]
   1: source

[jcheng5]

The problem has to do with stack trace stripping; if you set options(shiny.fullstacktrace=TRUE) you'll see that the info is all there, just getting pruned out in the observeEvent case because it's missing a ..stacktraceon.. somewhere.