[Rd] R-devel Digest, Vol 229, Issue 21

[Georgi Boshnakov]

> Should I have relied upon \Sexpr{#1} working inside user-defined macros? Georgi N. Boshnakov's Rdpack does similar things (and has been an inspiration for my tricks).

Glad to be inspiration:).  There are no tricks in Rdpack and
using \Sexpr{#1} in user Rd macros is ok but care is needed. In your example:

\newcommand{\bib}{\Sexpr[stage=build,results=rd]{bibentry(#1)}}
\bib{'Misc',
  author = person('J.', 'Doe'), year = 2022,
  title = paste0(
    'A ', rawToChar(as.raw(0x5c)),
    'enc{møøse}{moose} bit my sister once'
#       ^-----^^-----^--- in these four places
  )
}

I am surprised that the above macro ever worked as intended. 'bibentry' returns a 'bibentry' object and \Sexpr converts it with 'as.character'. There is no as.character method for bibentry, so the result would be something like list(list(given = "J.", family = ...)). That is what I get on Ubuntu with R-devel (r82022 2022-03-29) and non-R-devel. I put the above in a package. If you are running a command on the console the bibentry object will be printed ok since the default print method for bibentry uses the text style. In fact, if the body of your macro is replaced by

capture.output(print(bibentry))

I get the desired result in the built documentation:

Doe J (2022). “A møøse bit my sister once.”

One thing to be aware of is that the argument of \Sexpr is R-like but that of user defined macros is not. When the parser escapes the argument to your macro, it doesn't know that in your case it is R code (in the invocation of '\bib' above), since it would need to 'understand' the body of your macro and notice that you are using #1 in R code, not in LaTeX-like text. This would explain the error message you get. 

I don't know if something was fixed between the R-devel you used and probably the most recent one I did but reproducible example and system information would be helpful. I have some simple packages used in bug reports at https://github.com/GeoBosh/reprexes 

Georgi Boshnakov


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Today's Topics:

   1. Backslashes, braces, \Sexpr and user macros (Ivan Krylov)

----------------------------------------------------------------------

Message: 1
Date: Fri, 25 Mar 2022 18:32:23 +0300
From: Ivan Krylov <krylov.r00t using gmail.com>
To: r-devel using r-project.org
Subject: [Rd] Backslashes, braces, \Sexpr and user macros
Message-ID: <20220325183223.3ab20393-2358 using arachnoid>
Content-Type: text/plain; charset="utf-8"


Hello R-devel,

I had been using an Rd trick that runs afoul of the changes in r81965[*]. After the change, there seems to be a problem with any user-defined macro that takes R code, forwards it to \Sexpr and gets passed a string literal containing '{':

\newcommand{\RRd}{\Sexpr[stage=build,results=rd]{#1}}
\RRd{x <- 'a string with { inside it'; 'okay'}

R-4.1.3: okay
R-devel: Error: x.Rd: '\{' is an unrecognized escape in character string starting "'a string with \{"
Execution halted

My actual use case is a macro that forwards its argument to \Sexpr{tools::toRd(bibentry(...))}. I've been trying to pass \enc{}{} as an argument to bibentry; previously, I had to use a workaround to create the backslash, but now any braces (in addition to backslashes) inside string literals also result in errors:

\newcommand{\bib}{\Sexpr[stage=build,results=rd]{bibentry(#1)}}
\bib{'Misc',
  author = person('J.', 'Doe'), year = 2022,
  title = paste0(
    'A ', rawToChar(as.raw(0x5c)),
    'enc{møøse}{moose} bit my sister once'
#       ^-----^^-----^--- in these four places
  )
}

R-4.1.3: Doe J (2022). “A møøse bit my sister once.”

R-devel: Error: x.Rd: '\{' is an unrecognized escape in character string starting "'enc\{"
Execution halted

Should I have relied upon \Sexpr{#1} working inside user-defined macros? Georgi N. Boshnakov's Rdpack does similar things (and has been an inspiration for my tricks). I'll be glad to re-write some of my Rd to achieve the same result using less crazy tricks, assuming there is a right way to do that.

--
Best regards,
Ivan

[*]
https://github.com/r-devel/r-svn/commit/7ccd166735e6b978023b85fc9aa4845af8c0c241