[Rd] Including mode='wb' in download.file() for .xlsx files on Windows ?

[Hernando Cortina]

Hello all, regarding download.file():

On Windows, if mode is not supplied (missing()) and url ends in one of
‘⁠.gz⁠’, ‘⁠.bz2⁠’, ‘⁠.xz⁠’, ‘⁠.tgz⁠’, ‘⁠.zip⁠’, ‘⁠.jar⁠’, ‘⁠.rda⁠’,
‘⁠.rds⁠’, ‘⁠.RData⁠’ or ‘⁠.pdf⁠’, mode = "wb" is set so that a binary
transfer is done to help unwary users.

May I suggest possibly including .xlsx files to the list of extensions
that get this treatment?

Downloading such files may be a quite common activity in the R
community and having to manually add mode=”wb” may indeed catch
Windows users unaware, particularly if they are coming from Linux or
Mac where this is not necessary.

I understand that it’s hard to know when to stop when adding
additional extensions.  That said, .xlsx is quite ubiquitous in the
wild and standardized under ECMA-376.

I hope this might be helpful to others, and thank you for your consideration.
Hernando
---------------

 The change in src/library/utils/R/Windows/download.file.R would be:

…

if(missing(mode) && length(grep("\\.(gz|bz2|xz|tgz|zip|jar|rd[as]|RData|xlsx)$",

                    URLdecode(url))))

        mode <- "wb"

…