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modify_tree() (or map_vec()?) chokes on S3 inside shiny::reactive() #1155

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maxheld83 opened this issue Nov 14, 2024 · 0 comments
Open

modify_tree() (or map_vec()?) chokes on S3 inside shiny::reactive() #1155

maxheld83 opened this issue Nov 14, 2024 · 0 comments

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@maxheld83
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I ran into a very weird and subtle behavior involving modify_tree() on a list which includes

  1. shiny::reactive()s
  2. around some S3 class

take any of them away (unclass() the S3 class) or don't use a reactive, and the problem goes away.

Here's the reprex:

shiny::testServer(
  app = function(input, output, session) {
    # fails with this object
    obj <- reactive(htmltools::HTML("foo"))
    # works without a reactive
    # obj <- htmltools::HTML("foo")
    # works with class removed
    # obj <- reactive(unclass(htmltools::HTML("foo")))
    purrr::modify_tree(
      x = obj,
      is_node = function(x) is.reactive(x) || is.list(x),
      pre = function(x) {
        if (is.reactive(x)) {
          x <- rlang::exec(x)
        }
        x
      }
    )
  },
  # no actual tests here
  expr = stopifnot(TRUE)
)

As is, this fails with:

Error in `map_vec()`:
! Can't convert `<list>[[1]]` <character> to <html>.

This makes sense to me: you can't convert a list to html.
(html is the S3 class assigned to returns by htmltools::HTML()).

What I don't understand is:

  • why modify_tree() (via map_vec()) would try to do this in the first place
  • why this wouldn't also affect the other examples

I'm not sure this is a bug, but it sure struck me as unexpected behavior.
(Or maybe I'm just being boneheaded and missing something).

session_info():

─ Session info ────────────────────────────
 setting  value
 version  R version 4.4.2 (2024-10-31)
 os       macOS Sequoia 15.1
 system   aarch64, darwin20
 ui       X11
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       Europe/Berlin
 date     2024-11-14
 pandoc   3.5 @ /opt/homebrew/bin/pandoc

─ Packages ────────────────────────────────
 package     * version date (UTC) lib source
 backports     1.5.0   2024-05-23 [1] CRAN (R 4.4.0)
 brio          1.1.5   2024-04-24 [1] RSPM
 bslib         0.8.0   2024-07-29 [1] RSPM
 cachem        1.1.0   2024-05-16 [1] RSPM
 checkmate     2.3.2   2024-07-29 [1] CRAN (R 4.4.0)
 cli           3.6.3   2024-06-21 [1] CRAN (R 4.4.0)
 desc          1.4.3   2023-12-10 [1] RSPM
 devtools    * 2.4.5   2022-10-11 [1] RSPM
 digest        0.6.37  2024-08-19 [1] CRAN (R 4.4.1)
 ellipsis      0.3.2   2021-04-29 [1] CRAN (R 4.4.0)
 fansi         1.0.6   2023-12-08 [1] CRAN (R 4.4.0)
 fastmap       1.2.0   2024-05-15 [1] CRAN (R 4.4.0)
 fs            1.6.5   2024-10-30 [1] CRAN (R 4.4.1)
 glue          1.8.0   2024-09-30 [1] CRAN (R 4.4.1)
 htmltools     0.5.8.1 2024-04-04 [1] CRAN (R 4.4.0)
 htmlwidgets   1.6.4   2023-12-06 [1] CRAN (R 4.4.0)
 httpuv        1.6.15  2024-03-26 [1] RSPM
 jquerylib     0.1.4   2021-04-26 [1] CRAN (R 4.4.0)
 jsonlite      1.8.9   2024-09-20 [1] CRAN (R 4.4.1)
 later         1.3.2   2023-12-06 [1] RSPM
 lifecycle     1.0.4   2023-11-07 [1] RSPM
 magrittr      2.0.3   2022-03-30 [1] CRAN (R 4.4.0)
 memoise       2.0.1   2021-11-26 [1] RSPM
 mime          0.12    2021-09-28 [1] CRAN (R 4.4.0)
 miniUI        0.1.1.1 2018-05-18 [1] RSPM
 pak         * 0.8.0   2024-08-26 [1] CRAN (R 4.4.1)
 pillar        1.9.0   2023-03-22 [1] CRAN (R 4.4.0)
 pkgbuild      1.4.5   2024-10-28 [1] CRAN (R 4.4.1)
 pkgload       1.4.0   2024-06-28 [1] CRAN (R 4.4.0)
 profvis       0.4.0   2024-09-20 [1] CRAN (R 4.4.1)
 promises      1.3.0   2024-04-05 [1] CRAN (R 4.4.0)
 purrr         1.0.2   2023-08-10 [1] CRAN (R 4.4.0)
 R6            2.5.1   2021-08-19 [1] CRAN (R 4.4.0)
 Rcpp          1.0.13  2024-07-17 [1] RSPM
 remotes       2.5.0   2024-03-17 [1] CRAN (R 4.4.0)
 reprex      * 2.1.1   2024-07-06 [1] RSPM
 rlang         1.1.4   2024-06-04 [1] CRAN (R 4.4.0)
 rprojroot   * 2.0.4   2023-11-05 [1] CRAN (R 4.4.0)
 sass          0.4.9   2024-03-15 [1] CRAN (R 4.4.0)
 sessioninfo   1.2.2   2021-12-06 [1] CRAN (R 4.4.0)
 shiny       * 1.9.1   2024-08-01 [1] RSPM
 testthat      3.2.1.1 2024-04-14 [1] RSPM
 urlchecker    1.0.1   2021-11-30 [1] RSPM
 usethis     * 3.0.0   2024-07-29 [1] CRAN (R 4.4.0)
 utf8          1.2.4   2023-10-22 [1] RSPM
 vctrs         0.6.5   2023-12-01 [1] CRAN (R 4.4.0)
 withr         3.0.2   2024-10-28 [1] CRAN (R 4.4.1)
 xtable        1.8-4   2019-04-21 [1] RSPM

 [1] /Users/max/Library/R/arm64/4.4/library
 [2] /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library

───────────────────────────────────────────

Why though?

Fair question.

My shiny module deals with inputs which can be a varying, nested list of reactives and non-reactives.
To deal with this list (show them) I first need to make all these leafs the same (i.e. rlang::exec() them and some other stuff).
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@maxheld83