BiocGenerics package interferes with some mlr3 printers

[mb706]

library("mlr3")
BiocGenerics::which(FALSE)
#> integer(0)
resample(tsk("iris"), lrn("classif.rpart"), rsmp("holdout"))
#> INFO  [16:12:14.448] [mlr3] Applying learner 'classif.rpart' on task 'iris' (iter 1/1)
#> <ResampleResult> with 1 resampling iterations
#> Error in as.vector(x, "character") : 
#>   cannot coerce type 'environment' to vector of type 'character'

The BiocGenerics package gets loaded indirectly when using Bioconductor packages, e.g. NMF:

library("mlr3")
library("NMF")
#> Loading required package: registry
#> Loading required package: rngtools
#> Loading required package: cluster
#> NMF - BioConductor layer [OK] | Shared memory capabilities [OK] | Cores 2/2
resample(tsk("iris"), lrn("classif.rpart"), rsmp("holdout"))
#> INFO  [16:15:25.294] [mlr3] Applying learner 'classif.rpart' on task 'iris' (iter 1/1)
#> <ResampleResult> with 1 resampling iterations
#> Error in as.vector(x, "character") : 
#>   cannot coerce type 'environment' to vector of type 'character'

The problem is that BiocGenerics registers a format.list() function, which then triggers the data.table printer to call format.list() on our R6-valued list columns.

[mb706]

Also reported here: Rdatatable/data.table#6392

[berndbischl]

I don't really think we can do much on our side. This must be fixed in datatable