R files generating knitr templates are parsed as Rmd

[MichaelChirico]

If I have a file that generates knitr templates, e.g.

writeLines('
CreateTemplate <- function(x) {
return(sprintf("
```{r code}
foo <- function(x) x+%d
foo(5)
```", x))
}', tmp <- tempfile())

parse(tmp) works just fine, however, lintr assumes this is an Rmd based on matching some chunk regex:

lintr::lint(tmp)
# /tmp/RtmpN8X7Dj/file3d0536f05e5d:4:1: error: Missing chunk end for chunk (maybe starting at line 4).
# ```{r code}
# ^

Should we try parsing the file as R code first, then checking Rmd chunks afterwards?

[AshesITR]

Or maybe check for valid YAML front matter to detect Rmd?

[MichaelChirico]

the front matter might also be part of a template, so we'll have to force it to come at the top of the file (perhaps following whitespace)...
is there any requirement for Rmd to have YAML? i.e. is it possible to knit an Rmd that only uses some defaults?

[AshesITR]

Not entirely sure, but IINM a YAML front matter starting at line 1 is required (or at least present in 99.999% of Rmd scripts)

I suggest taking a look at knitrs code base. IIRC it has a parse front matter function.