jcheng5

Promise Domains

(This is a departure from Promises/A+ spec. It's needed to support the use of promises with Shiny, especially reactivity, but also seems like it'd be useful for logging, profiling, error handling...)

There are some places in R and in Shiny especially, where it's very useful to set up changes to the environment temporarily, execute some user-provided code, and then change the environment back to its original state.

For one example, consider the capture.output function. This won't work:

capture.output({

MarkEdmondson1234

library(shiny)

#' Safe subset
#'
#' @param df Dataframe
#' @param column One name of column to subset within
#' @param subset Vector of entries in column to subset to
#'
#' If column not in df, returns back the df
safeSubset <- function(df, column, subset){