[R-pkg-devel] Writing to files without altering working directory in R package

[Boris Steipe]

Have you considered putting the explicit case into a comment? Something like ...

# For output to a CSV file, we would assign: myCSV <- "myResults.csv"
# ... but for this example we will use the value of tempfile() as the file name:
myCSV <- tempfile()
results <- doSomething(x, csvFile = myCSV, ...)


I often find the lack of comments in examples less than optimal for didactic reasons.

$0.02

Boris



> On 2019-05-07, at 18:50, Duncan Murdoch <murdoch.duncan using gmail.com> wrote:
> 
> On 07/05/2019 6:44 p.m., Uwe Ligges wrote:
>> On 07.05.2019 19:57, Duncan Murdoch wrote:
>>> On 06/05/2019 12:16 p.m., Jim Hester wrote:
>>>> For what it's worth, the recommendation to use `tempfile()` is very
>>>> confusing to R users.
>>>> 
>>>> Often users (particularly new users) jump directly to examples when
>>>> reading documentation and when you have these more complicated
>>>> examples they do not realize they can just use a simple string
>>>> literal.
>>>> 
>>>> See https://github.com/tidyverse/readr/issues/635 for an issue where
>>>> multiple users explicitly request examples which do _not_ use
>>>> `tempfile()`.
>>> 
>>> I think beginners rarely like the help pages, and that's really to be
>>> expected:  help pages need to be complete and correct, and beginners
>>> really need a small subset of possibilities.  Beginners need tutorials.
>>> 
>>> In the Github issue, you mentioned pollution of the working directory,
>>> but I think a bigger problem is destruction of user data, e.g. if a user
>>> has a file "wine.csv", and the example writes to that file.
>>> 
>>> So you need to do something to protect users.  I think making examples a
>>> little complicated by using setwd(tempdir()) with a literal filename, or
>>> writing to tempfile() is worth it.
>> Thank you, Duncan. Well, setwd(tempdir()) should be made local to the
>> examples if used at all, as the user may not expect to have the working
>> directory changed.
> 
> Yes, I agree.
> 
> Duncan Murdoch
> 
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