On 2025-12-29 7:34 p.m., Rafael H. M. Pereira wrote:
Hi all,
I would very much appreciate your thoughts on this situation.
# context
I received an email from Prof Ripley saying that my package is not "falling
gracefully". Error report here
https://www.stats.ox.ac.uk/pub/bdr/Rblas/ATLAS/aopdata.out
The error happens in the code below. You see, in the case of an internet
connection issue, the aopdata::read_population() function returns a silent
NULL plus an informative message, as it should. So my package does in fact
fail gracefully whenever an internet connection is unavailable.
In this case, though, the error is actually happening in the ggplot2 call.
Because the df object is NULL, ggplot2 cannot find the "P001" column. In
short, the package itself does follow CRAN's policy when there is an
eventual internet connection issue, but the subsequent code throws an error
in such a case.
Given this behavior, I’m not sure there is a change I could make to my
package that would fully prevent this situation, other than removing
vignettes that demonstrate how to use the function outputs, which I would
prefer to avoid if possible.
The vignette is part of your package, so you have control over what
errors it throws. Follow Dirk's advice, add a check for NULL. I'd make
the test a little more informative than his code, adding something like
message("The download appears to have failed.")
when a NULL is returned.
Duncan Murdoch
# the situation
When I asked for advice, a kind Cran maintainer said: "So it is not good
enough to have a function return NULL when the subsequent code will throw
an error when it gets that NULL."
So here is the situation. The Cran Policy (see it below) requires *the
package* to fail gracefully. It does not mention subsequent code. Imho, it
should not require any subsequent code to fail gracefully. As a
package developer, I only have control over the functioning of my package,
I cannot control what code users will use to analyze the output of my
package functions.
If necessary, I will simply not run the ggplot calls in my vignettes and
render pre-generated plots saved in .png. I feel this would be a bad
solution to keep the package on CRAN, though. I would really appreciate
your thoughts on this.
best,
Rafael Pereira
*Cran Policy asks that:*
- Packages which use Internet resources should fail gracefully with
an informative
message if the resource is not available or has changed (and not give a
check warning nor error)
# code causing the error
library(aopdata)
library(ggplot2)
df <- aopdata::read_population
<https://ipeagit.github.io/aopdata/reference/read_population.html>(
city = 'Fortaleza', year = 2010, geometry = TRUE, showProgress =
FALSE )
ggplot() +
geom_sf(data=subset(df, P001>0), aes(fill=P001), color=NA, alpha=.8) +
scale_fill_distiller(palette = "YlOrRd", direction = 1)+
labs(title='Population distribution', fill="Total population") +
theme_void()
best,
Rafael Pereira
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