How to web search R error messages from within R

search_error.md

Friendly error messages are unfortunately not one of R's strengths. Often, running buggy code will yield something like:

DF <- subset(mtcars, cyl > 4)
df$mpg <- round(df$mpg)

#> Error in df$mpg : object of type 'closure' is not subsettable

Huh? A closure is an R function with an enclosing environment (that is, one that can access the environment where it was defined). df is one such function, which gives the F distribution. In plain English, the error message is saying you can't extract an element from a function as if it were a vector.

But how many R novices who run into this error for the first time can figure that out on their own? (I certainly couldn't!). Then the only way out is to Google the error message and find an explanation. But copying the code into a web browser breaks focus and wastes time. We can automate that task.

First, define a function to Google a query from within R, which is suprisingly simple:

google <- function(query) {
    browseURL(paste0("http://www.google.com/search?q=", query))
}

We just have to create a query URL and send it to browseURL. Extracting the error message is a little more involved, but not too bad:

# Google most recent error message
search_error <- function(stackoverflow = TRUE) {
    if ((error <- capture.output(cat(geterrmessage()))[1]) == "") {
    cat("No error messages in buffer")
    return()
    }
    google(paste(error, ifelse(stackoverflow, "site:stackoverflow.com", "")))
}

geterrmessage does...pretty much that. capture.output and cat get the text without the ending newline. Error messages can have length greater than 1 (a lot of tidyverse error messages are like that), so I subset only the first element to capture the most essential information. The rest is details: an if clause to abort if there are no recorded errors (if only!), and an argument letting you restrict the search to StackOverflow.

I hope these functions relieve some of the tedium of debugging.