tidyselect should not be added to global search path

[dernst]

Prework

• Read and abide by drake's code of conduct.
• Search for duplicates among the existing issues, both open and closed.
• Advanced users: verify that the bug still persists in the current development version (i.e. remotes::install_github("ropensci/drake")) and mention the SHA-1 hash of the Git commit you install.

Description

Package tidyselect is added to the global search path by use of require. I assume requireNamespace would be more appropriate as subsequent calls to tidyselect functions are qualified by their package name.
The problem was tested with the latest github version as of 1 hour ago.

Reproducible example

library(drake)
"package:tidyselect" %in% search()  # correctly outputs FALSE
drake:::drake_tidyselect_cache()
"package:tidyselect" %in% search()  # now incorrectly outputs TRUE

Expected result

The search() path should not have been altered.

Session info

> sessionInfo()
R version 3.6.3 (2020-02-29)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.3 LTS

Matrix products: default
BLAS/LAPACK: /data/home/ernst/.local/openblas/lib/libopenblas_haswellp-r0.3.9.so

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  methods   base

other attached packages:
[1] tidyselect_1.1.0  drake_7.12.2.9000

loaded via a namespace (and not attached):
 [1] txtq_0.2.0        prettyunits_1.1.1 fansi_0.4.1       crayon_1.3.4
 [5] digest_0.6.25     assertthat_0.2.1  R6_2.4.1          backports_1.1.7
 [9] storr_1.2.1       magrittr_1.5      progress_1.2.2    rlang_0.4.6
[13] cli_2.0.2         data.table_1.12.8 filelock_1.0.2    vctrs_0.3.1
[17] tools_3.6.1       glue_1.4.1        purrr_0.3.4       igraph_1.2.5
[21] hms_0.5.3         parallel_3.6.1    compiler_3.6.1    pkgconfig_2.0.3
[25] base64url_1.4

[wlandau]

tidyselect is not required for essential drake functionality, but it is required for helper functions if the user supplies tidyselect syntax, so I put it in Suggests:.

drake/DESCRIPTION

Line 148 in 47ecd87

tidyselect (>= 1.0.0),

[wlandau]

I still feel this is the right decision because it helps limit the number of strict dependencies of the package. One consequences is that certain functions will try to automatically load tidyselect. The behavior may seem unusual, but it is unavoidable if we want drake to be easy for most users to install.

[dernst]

which_clean seems to always attach tidyselect if it is installed (because drake_tidyselect_cache explicitly calls require, which would normally fail CRAN checks so that's why it's wrapped in eval/parse). How would one go about using which_clean without attaching tidyselect other than removing tidyselect?

[wlandau]

For tidyselect selectors like starts_with() to work normally, either the package has to be attached or we need to import and re-export tidyselect in drake. I was avoiding the latter because it requires tidyselect to be a strong dependency. Switched in 4141c98.