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The goal of pkgcond is to facilitate the creation of errors, warnings, and messages (collectively called signals or conditions) that are more informative than the base versions.

Signals can be created through pkg_error(), pkg_warning() and pkg_message(). When these are used a scope is computed and used to create errors, warnings and signals, respectively, with classes set to the combinations of the scope. The scope, while is could be set explicitly, infers where the condition is created, and will typically include the function call and package name.


You can install the released version of pkgcond from CRAN with:


Understanding Scope

Let’s consider a toy example to understand the scope. Say that we are creating a package named hw with a function hello_world() defined as follows:

hello_world <- function(greeting = 'hello', who = 'world'){
    if (!is.character(greeting) && length(greeting) == 1L) 
        pkg_error("greeting must be a string.")
    if (!is.character(who) && length(who) == 1L) 
        pkg_error("who must be a string.")
    pkg_message(paste(greeting, who))

If the function is called with the defaults the pkg_message() function will be called. The effect is the same as if a base::message() call were here; A message with “hello world” would appear in the console. However, pkg_message() does a little more. The base call would create a ‘message’ object and signal it. With pkg_message() since it was invoked inside the hello_world() function inside the hw package the scope would be set to c('hw', 'hello_world') This in turn would be used to create the message signal with the following classes.

The pkg_error() and pkg_warning() functions have similar scoping however with error and warning replacing message, respectively.

This becomes really useful if one wishes to capture conditions. This is done with the tryCatch() function. In this way one can easily catch the conditions that originate from a specific function call or a specific package while passing others through or handling them differently.

tryCatch( hello_world("die", stop)
        , "hw::hello_world-error" = function(cond){
            # This would handle the error that is raised from passing
            # `stop` into the `hello_world function()
        , "hw-condition" = function(cond){
            # This would capture all error originating in the hw package
            # that were signaled using any of the `pkg_*` functions.
        # Errors that did not originate from the hw package or were created 
        # with the traditional stop, warning, or message functions
        # will be passed through since they will not be "Caught"

Helpers included:

These functions are included with pkgcond to help create error messages.


The pkgcond package is developed by the R Documentation Task Force, an R Consortium Infrastructure Steering Committee working group.