do not eval vignette chunks which should error (use purl=FALSE)

[ben-schwen]

Currently our CI pipelines are erroring, since they error on parts of the vignettes where they are supposed to error.

According to knitr doc setting error=0 should be the right

0 will keep evaluating after errors as if you had pasted the text into a terminal;

but these will still result in R CMD check erroring, hence, purl=FALSE

[jangorecki]

Afaiu this will result into different output on the vignette. Error won't be printed. Please add error message below the call that mean to error, prefixing with #

[tdhock]

actually it would be better to use purl=TRUE as below, which includes the error output in the rendered vignette, but does not cause an error when building the vignette.

```{r error=TRUE, purl=TRUE}
mlr3::ResamplingCV$new()$instantiate(reg.task)
```

example: search for "error:" in https://cloud.r-project.org/web/packages/mlr3resampling/vignettes/ResamplingSameOtherSizesCV.html

[ben-schwen]

@tdhock Ty for the suggestion. Knitted vignette knitr::knit("vignettes/datatable-programming.Rmd") looks good! But I just tried it with the docker image and R CMD check still errors.

[ben-schwen]

Using eval=FALSE and adding the output as comment seems the way to go as suggested by Jan

[tdhock]

??? what is the error you see with the docker image ???

[ben-schwen]

??? what is the error you see with the docker image ???

With error = TRUE, purl = TRUE R CMD check is failing with the same error

 ERROR
Errors in running code in vignettes:
when running code in ‘datatable-programming.Rmd’
  ...

> my_subset = function(data, col, val) {
+     subset(data, col == val)
+ }

> my_subset(iris, Species, "setosa")

  When sourcing ‘datatable-programming.R’:
Error: object 'Species' not found
Execution halted

* checking re-building of vignette outputs ... OK
* checking PDF version of manual ... OK
* DONE

Status: 1 ERROR, 2 NOTEs

[tdhock]

this is a new error in my other packages as well (which use purl=TRUE) so I'm thinking this may be a bug in knitr. I checked their issues and found yihui/knitr#2338 where I asked for a work-around.

[tdhock]

sorry for the confusing suggestions, but I think the solution is to use purl=FALSE instead of TRUE in chunk options.
(I have several CRAN packages that are not failing checks which use purl=FALSE)

[ben-schwen]

@tdhock I just checked with the docker image. error=TRUE, purl=FALSE works indeed, ty for the suggestion and clarification!

[MichaelChirico]

LGTM, but will let Toby approve as I think he's more familiar with the {knitr} details here.

[tdhock]

thanks