[R-pkg-devel] URL syntax causes R CMD build failure - a fix

[Greg Hunt]

The percent encoded characters appear to be valid in that URL, suggesting
that rejecting them is an error. That kind of error could occur when the
software processing them converts them back to a non-unicode character set.

On Sun, 3 Sep 2023 at 4:34 am, J C Nash <profjcnash using gmail.com> wrote:

> I'm posting this in case it helps some other developers getting build
> failure.
>
> Recently package nlsr that I maintain got a message that it failed to
> build on
> some platforms. The exact source of the problem is still to be illuminated,
> but seems to be in knitr::render and/or pandoc or an unfortunate
> interaction.
> An update to pandoc triggered a failure to process a vignette that had been
> happily processed for several years. The error messages are unhelpful, at
> least
> to me,
>
>     Error at "nlsr-devdoc.knit.md" (line 5419, column 1):
>     unexpected end of input
>     Error: pandoc document conversion failed with error 64
>     Execution halted
>
> Unfortunately, adding "keep_md: TRUE" (you need upper case TRUE to save it
> when
> there is no error of this type), did not save the intermediate file in this
> case. However, searching for "pandoc error 64" presented one web page
> where the author
> used brute force search of his document by removing / replacing sections
> to find
> the line(s) that caused trouble. This is a little tedious, but effective.
> In my
> case, the offending line turned out to be a copied and pasted URL
>
> https://en.wikipedia.org/wiki/Levenberg%E2%80%93Marquardt_algorithm
>
> The coded characters can be replaced by a hyphen, to give,
>
> https://en.wikipedia.org/wiki/Levenberg-Marquardt_algorithm
>
> and this, when pasted in Mozilla Firefox at least, will go to the
> appropriate
> wikipedia page.
>
> I'd be interested in hearing from others who have had similar
> difficulties. I
> suspect this is relatively rare, and causing some sort of infelicity in the
> output of knitr::render that then trips up some versions of pandoc, that
> may,
> for instance, be now applying stricter rules to URL syntax.
>
> Best,
>
> John Nash
>
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