`methods` not loaded/working when using lubridate::object notation in Rscript

[mmuurr]

I'm having some trouble executing functions that rely on package methods when being run via Rscript. I already know that methods is not attached via Rscript, but it should be loaded (and usable) by the dependent packages and accessible via their package namespaces, at least I thought so...

Example R script (executed via Rscript):

#!/usr/bin/Rscript

sessionInfo()

tryCatch({
    str(lubridate::days(30))
}, error = function(e) {
    print(e)
})

sessionInfo()

tryCatch({
    str(lubridate::days(30))
}, error = function(e) {
    print(e)
})

library(methods)
str(lubridate::days(30))
sessionInfo()

Output, with my comments and questions mixed below ...

First, here's the startup sessionInfo():

# sessionInfo()

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  base

As expected with Rscript, package methods is not attached, nor loaded.

Now, what's surprising to me is that I thought the lubridate::days(30) call would load methods, since the lubridate package does "Depend" on methods, as verified in lubridate's DESCRIPTION file. Instead, I get the error:

# tryCatch({
#     str(lubridate::days(30))
# }, error = function(e) {
#     print(e)
# })

<simpleError in .setupMethodsTables(fdef, initialize = TRUE): trying to get slot "group" from an object of a basic class ("NULL") with no slots>

But now I'm really confused, because methods does seem to have been loaded, as seen with the next sessionInfo() call:

# sessionInfo()  

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  base

loaded via a namespace (and not attached):
[1] magrittr_1.5         tools_3.2.2          lubridate_1.5.6.9000
[4] stringi_1.0-1        methods_3.2.2        stringr_1.0.0

Just to be sure (about my confusion), let's try calling lubridate::days(30) again:

# tryCatch({
#     str(lubridate::days(30))
# }, error = function(e) {
#     print(e)
# })

<simpleError in .setupMethodsTables(fdef, initialize = TRUE): trying to get slot "group" from an object of a basic class ("NULL") with no slots>

Same error.

OK, now let's explicitly attach methods and try the lubridate::days(30) call again:

# library(methods)
# str(lubridate::days(30))

Formal class 'Period' [package "lubridate"] with 6 slots
  ..@ .Data : num 0
  ..@ year  : num 0
  ..@ month : num 0
  ..@ day   : num 30
  ..@ hour  : num 0
  ..@ minute: num 0

That worked!
What changed by specifically attaching methods?:

# sessionInfo()

R version 3.2.2 (2015-08-14)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Amazon Linux AMI 2015.09

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] methods   stats     graphics  grDevices utils     datasets  base

loaded via a namespace (and not attached):
[1] magrittr_1.5         tools_3.2.2          lubridate_1.5.6.9000
[4] stringi_1.0-1        stringr_1.0.0

methods is not attached (as opposed to loaded-but-not-attached).

I know I could solve all the headaches by simply including library(methods) atop scripts, but this seems silly, as I thought loading methods would have the same affect to the underlying packages (due to R's package namespacing), without me having to know specifically if any package I use relies on methods or not.

Does this seem like an R problem, or possibly a namespace issue with lubridate?

[vspinu]

methods namespace is special somehow. You can also solve it by library(lubridate). Not much we can do at lubridate side. methods is already listed as our dependency. This is a duplicate of #314.

[shrektan]

Its how rscript works and there's little to do with lubridate. Either explicitly attach methods in your script or make a pull request that is adding method in the import of the description file ~ I guess.