How does R (RGui) parse multiline character strings? - r

Question

The RGui (Windows; R version 3.5.3) appears to ignore tab characters that occur at the beginning of a line within a character string (press CTRL+R over the lines of code):
# REPLACE "<TAB>" WITH AN ACTUAL TAB CHARACTER TO GET THE CODE INTENDED BELOW.
foo <- 'LINE1
<TAB>LINE2
<TAB>LINE3
'
foo
# [1] "LINE1\nLINE2\nLINE3\n"
longstring <- removetabsatbeginningoflines('
<TAB>Sometimes I have really long strings that I format
<TAB>so that they read nicely (not with too long of a
<TAB>line length). Tabs at the beginning of the lines
<TAB>within a string preserve my code indenting scheme
<TAB>that I use to make the code more readable. If the
<TAB>tabs are not removed automatically by the parser,
<TAB>then I need to wrap the string in a function that
<TAB>removes them.')
The tab characters are preserved when the above code is source'd from a file.
Why doesn't RGui keep the tab characters?
Where is this behavior documented?
What other non-intuitive, related behaviors does RGui have with regard to parsing (multiline) strings?

Answer 1

I can't find anywhere that this is documented, so this is a worthwhile question to publicly answer.
If you are using RGui's built-in 'R Editor', then all Tab characters entered via the Tab key, or already existing in a text file that you have opened into the 'R Editor', will not be respected when submitting using Ctrl-R (This is difficult to represent here in an example given that tabs are stripped from answers).
I imagine the 'R Editor' is not meant to be used for serious code editing, and you may be better off using a dedicated IDE (e.g. RStudio) or more full-featured editor (e.g. Emacs, Notepad++).
You can route around this issue in RGui by manually replacing tabs as \t when editing in RGui, but this may not be appropriate if you want to keep actual Tabs in your file. Tabs will also be correctly processed when using source() to directly run the code stored in the text file.