R devel - Jul 2021 - \Sexpr[results=hide] produces \verb{ newlines }

Hello R-devel!

Here's an Rd file that produces a large empty area when converted to
HTML:

\name{repro}
\title{title}
\description{description}
\details{
  Hello
  \Sexpr[stage=build,results=hide]{
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    invisible(NULL)
    "" # workaround: remove results=hide and use the return value
  }
}

This seems to happen because \Sexpr gets expanded to \verb{ as many
newlines as there were code lines } by processRdChunk, by first storing
a newline for each line of the code:

https://github.com/wch/r-source/blob/d7a4ed9aaeee1f57c3c165aefa08b8d69dfe59fa/src/library/tools/R/RdConv2.R#L257

...and then the newlines get translated to \verb because res is
not empty:

https://github.com/wch/r-source/blob/d7a4ed9aaeee1f57c3c165aefa08b8d69dfe59fa/src/library/tools/R/RdConv2.R#L332

As long as Rd above doesn't stem from my misuse of \Sexpr, I would like
to propose the following patch, which seems to fix the problem:

Index: src/library/tools/R/RdConv2.R
==================================================================---
src/library/tools/R/RdConv2.R	(revision 80675)
+++ src/library/tools/R/RdConv2.R	(working copy)
@@ -329,6 +329,8 @@
 	    }
 	} else if (options$results == "text")
 	    res <- tagged(err, "TEXT")
+	else if (options$results == "hide")
+	    res <- tagged("", "COMMENT")
 	else if (length(res)) {
 	    res <- lapply(as.list(res), function(x) tagged(x, "VERB"))
 	    res <- tagged(res, "\\verb")

There are probably other ways of fixing this problem, e.g. by only
populating res if options$results != "hide" or only appending newlines
if res is non-empty.

-- 
Best regards,
Ivan

>>>>> Ivan Krylov 
>>>>>     on Thu, 29 Jul 2021 17:48:38 +0200 writes:
> Hello R-devel!
> 
> Here's an Rd file that produces a large empty area when converted to
> HTML:
> 
> \name{repro}
> \title{title}
> \description{description}
> \details{
>   Hello
>   \Sexpr[stage=build,results=hide]{
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     invisible(NULL)
>     "" # workaround: remove results=hide and use the return value
>   }
> }
> 
> This seems to happen because \Sexpr gets expanded to \verb{ as many
> newlines as there were code lines } by processRdChunk, by first storing
> a newline for each line of the code:
> 
>
https://github.com/wch/r-source/blob/d7a4ed9aaeee1f57c3c165aefa08b8d69dfe59fa/src/library/tools/R/RdConv2.R#L257
> 
> ...and then the newlines get translated to \verb because res is
> not empty:
> 
>
https://github.com/wch/r-source/blob/d7a4ed9aaeee1f57c3c165aefa08b8d69dfe59fa/src/library/tools/R/RdConv2.R#L332
> 
> As long as Rd above doesn't stem from my misuse of \Sexpr, I would like
> to propose the following patch, which seems to fix the problem:
> 
> Index: src/library/tools/R/RdConv2.R
> ==================================================================> ---
src/library/tools/R/RdConv2.R	(revision 80675)
> +++ src/library/tools/R/RdConv2.R	(working copy)
> @@ -329,6 +329,8 @@
>  	    }
>  	} else if (options$results == "text")
>  	    res <- tagged(err, "TEXT")
> +	else if (options$results == "hide")
> +	    res <- tagged("", "COMMENT")
>  	else if (length(res)) {
>  	    res <- lapply(as.list(res), function(x) tagged(x,
"VERB"))
>  	    res <- tagged(res, "\\verb")
> 
> There are probably other ways of fixing this problem, e.g. by only
> populating res if options$results != "hide" or only appending
newlines
> if res is non-empty.
Thank you, Ivan, for the example and patch,

I have implemented a version of your patch in my local copy of
R-devel and tested your example, also with  Rd2latex() ..
interestingly   Rd2txt()  does not produce the extra new lines
even without your patch.

I plan to commit your proposal after the weekend unless has 
reasons against that.

Best regards,
Martin

Hello Martin,

On Sat, 31 Jul 2021 22:14:17 +0200
Martin Maechler <maechler at stat.math.ethz.ch> wrote:
> I have implemented a version of your patch in my local copy of
> R-devel and tested your example, also with  Rd2latex() ..
> interestingly   Rd2txt()  does not produce the extra new lines
> even without your patch.
That's interesting, indeed. I think that flushBuffer() is responsible
for collapsing multiple blank lines into one in that case, but they do
get preserved in the buffer up to before that.
> I plan to commit your proposal after the weekend unless has 
> reasons against that.
Thanks for the review!

-- 
Best regards,
Ivan