Install "gradethis" package for code checking in "learnr" - r

Question

I am creating the interactive tutorials for R for presentation using "learnr" package. For code checking, I need the package "gradethis". When I try to install this package by
"
remotes::install_github("rstudio-education/gradethis")
"
it gives the error message:
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.
.
** byte-compile and prepare package for lazy loading
Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]) :
namespace ‘learnr’ 0.10.1 is being loaded, but >= 0.10.1.9007 is required
ERROR: lazy loading failed for package ‘gradethis’
─ removing ‘/private/var/folders/r2/3nmkgqc51q54tmhxl00tsk2908fpk9/T/RtmpaPONJB/Rinst15003850258d/gradethis’
-----------------------------------
ERROR: package installation failed
Error: Failed to install 'gradethis' from GitHub:
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The error message shows "‘learnr’ 0.10.1 is being loaded, but >= 0.10.1.9007 is required", however on CRAN, 0.10.1 is the latest version:
https://cran.r-project.org/web/packages/learnr/index.html
Can anyone help for this case? Many thanks.
The following show sessionInfo()
> sessionInfo()
R version 3.5.1 (2018-07-02)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS High Sierra 10.13.6
Matrix products: default
BLAS: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.5/Resources/lib/libRlapack.dylib
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_3.5.1 rjson_0.2.20 plyr_1.8.6
[4] markdown_1.1 htmltools_0.5.1.9000 tools_3.5.1
[7] base64enc_0.1-3 yaml_2.2.1 Rcpp_1.0.6
[10] rmarkdown_2.6 knitr_1.31 xfun_0.20
[13] digest_0.6.27 tutorial_0.4.3 rlang_0.4.10.9000
[16] evaluate_0.14

Answer 1

Since gradethis is still in a developmental/experimental phase, it is currently only available through GitHub at rstudio/gradethis. gradethis currently requires the developmental version of learnr which is also not yet on CRAN.
Installing both packages from their GitHub repositories will likely resolve your issues:
# install.packages("remotes") # require {remotes}
remotes::install_github("rstudio/learnr")
remotes::install_github("rstudio/gradethis")
Edit: The gradethis repository is now hosted under the rstudio GitHub organization.

Answer 2

Reproduced the error (macOS Big Sur 11.1 / Rstudio 1.3.1093 / R version 4.0.3) and solved the issue by uninstalling learnr with remove.packages("learnr") then installing gradethis with dependencies (including the required version of learnr) using remotes::install_github("rstudio-education/gradethis").
If you get a warning that "Skipping install of 'gradethis' from a github remote, the SHA1 has not changed since last install", use the command remotes::install_github("rstudio-education/gradethis", force = TRUE)
Successfully installing the packages requires the ability to compile from source (instructions for macOS Big Sur: https://stackoverflow.com/a/65334247/12957340)