r - devtools::build_vignettes yields "Error : invalid version specification 'pandoc.exe 1.13.1' -

r - devtools::build_vignettes yields "Error : invalid version specification 'pandoc.exe 1.13.1' -

after upgrading r 3.1.2 , updating packages can no longer build vignettes.

devtools::build_vignettes(shdoe)

the output follows:

building shdoe vignettes error : invalid version specification 'pandoc.exe 1.13.1' warning in engine$weave(file, quiet = quiet) : pandoc not available. please install pandoc. moving shdoe-intro.html, shdoe-intro.r inst/doc/ copying shdoe-intro.rmd inst/doc/

this after update of pandoc version 1.12.x (which yielded same error). os windows 7, , pandoc on path.

the problem associated way knitr parses version number returned by

pandoc.exe --version

which includes name pandoc called:

pandoc.exe 1.13.1 [...]

on windows, r's sys.which('pandoc') used knitr pandoc's executable yields <path pandoc>\pandoc.exe, leading above phone call pandoc's version cannot handled correctly knitr.

the faulty code introduced in knitr version 1.7 (before used rmarkdown::pandoc_available() check availablilty of pandoc).

a workaround set scheme variable rstudio_pandoc <path pandoc> (since knitr regards presence sufficient).

r knitr pandoc devtools