[Rd] Rd parser throws error for user macros invoked with empty argument

[Georgi Boshnakov]

Thanks for looking into this, empty string is the natural solution indeed.

Georgi


-----Original Message-----
From: Tomas Kalibera [mailto:tomas.kalibera using gmail.com] 
Sent: 25 May 2018 10:05
To: Georgi Boshnakov; r-devel using r-project.org
Subject: Re: [Rd] Rd parser throws error for user macros invoked with empty argument

Thanks for the report and the examples - and they do not have to be that 
verbose, it is enough to just define and use a command, e.g.

cat("\\newcommand{\\mac1}{MAC1:#1}\\mac1{}", file=f)
rd <- tools::parse_Rd(f)

Whenever you get an error message like "Value of SET_STRING_ELT() must 
be a 'CHARSXP' not a 'NULL'", there is a bug (at least the error message 
should be relevant/informative).

I am testing a patch that will allow empty arguments to macros (they 
will expand to an empty string, like in LaTeX).

Best
Tomas

On 05/14/2018 11:23 PM, Georgi Boshnakov wrote:
> Bug or feature?
>
> I get the following error from parse_Rd() when a user Rd macro (including system ones) is invoked with empty argument {},
> eg \mymacro{}:
>
> Error in tools::parse_Rd(fn) :
>    Value of SET_STRING_ELT() must be a 'CHARSXP' not a 'NULL'
>
> A full example is further below with the system macro \CRANpkg{}. In this example it doesn't make sense to use empty argument but the error is not specific to this particular macro.
>
> ------
> Georgi Boshnakov
>
>
> Create an Rd file containing system macro \CRANpkg{bibtex}, parse_Rd() is ok:
>
> =================
> fn <- tempfile()
> writeLines("\\name{dummyfun}
> \\alias{dummyfun}
> \\title{Dummy title}
> \\description{Dummy description}
> \\usage{
> dummyfun(x, ...)
> }
> \\arguments{
>    \\item{x}{a value.}
>    \\item{\\dots}{further arguments.}
> }
> \\details{
>      \\CRANpkg{bibtex}
> }
> ", fn)
>
>> tools::parse_Rd(fn)
> ...
> \details{
>      \href{{https://CRAN.R-project.org/package=bibtex}{\pkg{bibtex}}}
> }
>
> ================
>
> With empty argument - \CRANpkg{} - Rd parser throws error. Of course it is silly in this example but I have used it with other user defined  macros where it may make sense to have empty argument.
>
> ================
>> writeLines("\\name{dummyfun}
> \\alias{dummyfun}
> \\title{Dummy title}
> \\description{Dummy description}
> \\usage{
> dummyfun(x, ...)
> }
> \\arguments{
>    \\item{x}{a value.}
>    \\item{\\dots}{further arguments.}
> }
> \\details{
>      \\CRANpkg{}
> }
> ", fn)
>> tools::parse_Rd(fn)
> Error in tools::parse_Rd(fn) :
>    Value of SET_STRING_ELT() must be a 'CHARSXP' not a 'NULL'
>
> 	[[alternative HTML version deleted]]
>
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