Use Module to Set Breakpoint

Module of Shiny app needed to enable functionality to setting breakpoint. Must be used in the server part of Shiny app or in the function which is then used in the server part of app.

Usage

shinybreakpointServer(
  keyEvent = "F4",
  id = "shinybreakpoint",
  varName = "....envirr"
)

Arguments

keyEvent

key to run modal dialog with the functionality to set breakpoint. "F4" by default.

id

namespace used for all inputs and outputs in this module. "shinybreakpoint" by default. Change if in the app some other module is used which already has "shinybreakpoint" namespace.

varName

setting breakpoint is not equal to inserting only browser(), but also additional code, one of which is assignment operation. This parameter determines the variable name to assign value. "....envirr" by default. Change if this name is already in use somewhere in the app.

Value

Used for side effect - adds modal dialog to the Shiny app with the options to set breakpoint. Modal dialog is shown when the key specified in keyEvent is pressed.

App structure

One of the core concepts which founds this module is the necessity to re-run the objects present in the server part of app. This is possible only when these objects do not live directly in the server, but in the function which is then used in server. This naturally harmonizes with the modules, but it needs the separate function for objects which would be used directly in the server.

shinybreakpointServer module was developed having Bootstrap 5 in mind, that's why it is recommended to use bslib::bs_theme() to set up Bootstrap 5. Otherwise the UI experience will be worse.

Possibility to filter reactive context depending on specific input or output needs shiny::reactlog() enabled, which is done by set_filtering_by_id(). This line of code needs to be removed before app will be sent to production (which is of course true also for shinybreakpoint::shinybreakpointServer() line).

See example section below for the idea of how to include all of this requirements in the app. This can also be done by snippet() for new apps.

Filtering by Id

Filtering by Id is very experimental and may fail in not yet fully understandable way.

As long as shiny::reactlog() is enabled (by function set_filtering_by_id(), because this function is responsible also to manage some needed files in temporary directory, i.e. it won't be enough to just use options(shiny.reactlog = TRUE) or similar), it is possible to filter displayed source code based on input or output Id, i.e. only the relevant source code (reactives, observes and render* functions) will be shown. Two modes are available:

• Last changed input - last changed input is tracked automatically, i.e. nothing special needs to be done.

• Chosen Id - by holding Ctrl on PC or Cmd on Mac and hovering mouse over input or output, Id for this element will be saved (which will be indicated by displaying cursor of type 'progress' for a moment).

To successfully see all relevant source code for Id, it is necessary to ensure that code inside reactives, observes and render* functions is in curly ({}) brackets and that observes as well as shiny::bindEvent() (if used) have label, i.e. string is passed directly to the label parameter. Label needs to be unique across all labels and Ids. Additionally, if shiny::bindEvent() is used on render* function, label must be the same as the output Id. Because in this last case Id is masked by shiny::bindEvent(), there is no afraid that label and Id won't be unique.

Q option (exit) can't be use in debug mode to properly use filtering by Id. Please use c or f to close the debug mode - this will return to the app and then app can be stopped in usual way if needed.

Examples

# To run example, copy-paste to file, save
# the file and run the app. Then press "F4"
# to open the modal dialog.

if (FALSE) {

library(shiny)

shinybreakpoint::set_filtering_by_id() # TODO: remove

appServer <- function(input, output, session) {
  observe({
    input$num
  }, label = "observe_print_num_input")
}

shinyApp(
  ui = fluidPage(
    theme = bslib::bs_theme(5),
    numericInput("num", "Num", 0)
  ),
  server = function(input, output, session) {
    shinybreakpoint::shinybreakpointServer() # TODO: remove
    appServer(input, output, session)
  }
)
}