double quotes in restructuredText figure captions erroneously being converted to html

[trevorld]

I've recently noticed in my knitted README and blog posts that double quoted figure captions in restructuredText documents are now being erroneously converted to html in recent versions of {knitr}. {knitr} didn't used to do that so this seems to be new {knitr} bug introduced sometime "recently".

Contents of minimal example test.Rrst:

A simple restructuredText example
=================================

.. {r plot, fig.cap='A figure caption with \'single\' or "double" quotes'}
plot(1:5, rnorm(5))
.. ..

when knit by knitr::knit("test.Rrst") becomes:

A simple restructuredText example
=================================


.. sourcecode:: r
    

    plot(1:5, rnorm(5))

.. figure:: figure/plot-1.png
    :alt: A figure caption with 'single' or "double" quotes

    A figure caption with 'single' or "double" quotes

Instead of "double" we should instead see "double" in both places it appears in the knit .rst document.

Thanks!

xfun::session_info()
R version 4.1.0 (2021-05-18)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 20.04.2 LTS

Locale:
  LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8       
  LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8    LC_MESSAGES=C.UTF-8   
  LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C          
  LC_TELEPHONE=C         LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C   

Package version:
  askpass_1.1       brew_1.0.6        brio_1.1.2        cachem_1.0.5     
  callr_3.7.0       cli_3.0.0         clipr_0.7.1       commonmark_1.7   
  compiler_4.1.0    crayon_1.4.1      credentials_1.3.0 curl_4.3.2       
  desc_1.3.0        devtools_2.4.1    diffobj_0.3.4     digest_0.6.27    
  ellipsis_0.3.2    evaluate_0.14     fansi_0.5.0       fastmap_1.1.0    
  fs_1.5.0          gert_1.3.0        gh_1.3.0          gitcreds_0.1.1   
  glue_1.4.2        graphics_4.1.0    grDevices_4.1.0   highr_0.9        
  httr_1.4.2        ini_0.3.1         jsonlite_1.7.2    knitr_1.33.7     
  lifecycle_1.0.0   magrittr_2.0.1    markdown_1.1      memoise_2.0.0    
  methods_4.1.0     mime_0.11         openssl_1.4.4     parallel_4.1.0   
  pillar_1.6.1      pkgbuild_1.2.0    pkgconfig_2.0.3   pkgload_1.2.1    
  praise_1.0.0      prettyunits_1.1.1 processx_3.5.2    ps_1.6.0         
  purrr_0.3.4       R6_2.5.0          rappdirs_0.3.3    rcmdcheck_1.3.3  
  Rcpp_1.0.6        rematch2_2.1.2    remotes_2.3.0     rlang_0.4.11     
  roxygen2_7.1.1    rprojroot_2.0.2   rstudioapi_0.13   rversions_2.1.0  
  sessioninfo_1.1.1 stats_4.1.0       stringi_1.6.2     stringr_1.4.0    
  sys_3.4           testthat_3.0.3    tibble_3.1.2      tools_4.1.0      
  usethis_2.0.1     utf8_1.2.1        utils_4.1.0       vctrs_0.3.8      
  waldo_0.2.5       whisker_0.4       withr_2.4.2       xfun_0.24        
  xml2_1.3.2        xopen_1.0.0       yaml_2.2.1        zip_2.1.1    

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[cderv]

Thanks for the report.

A git bisect leads me to the issue being introduced by 17a64ff (#1900)

This PR touches fig.alt but for HTML output mainly. Something must have introduced the regression. I'll look into this.

[cderv]

And issue is from here:

knitr/R/hooks-html.R

Line 59 in 3237add

if (alt) return(escape_html(options$fig.alt %n% cap))

We should escape really only when the output format supports it.

[cderv]

However, this happens because the caption for rst output uses .img.cap(..., alt = "TRUE")
Maybe there is something to change in how it is handled for rst format

knitr/R/hooks-rst.R

Lines 5 to 19 in 3237add

	hook_plot_rst = function(x, options) {
	if (options$fig.show == 'animate') return(hook_plot_html(x, options))
	cap = .img.cap(options, alt = TRUE)
	# TODO: add all options for figure
	# See http://docutils.sourceforge.net/docs/ref/rst/directives.html#image
	# http://docutils.sourceforge.net/docs/ref/rst/directives.html#figure
	make_directive(
	'figure',
	paste0(opts_knit$get('base.url'), .upload.url(x)),
	c(align = if (options$fig.align == 'default') NULL else options$fig.align,
	alt = cap, width = options$out.width, height = options$out.height),
	cap
	)
	}

I don't know a lot about asciidoc yet. Is there a way to add alt text for figures ?

[trevorld]

I don't know a lot about asciidoc yet. Is there a way to add alt text for figures ?

I've never used asciidoc but the following documentation says to add an alt text then simply put it in between the square brackets of the image macro: https://docs.asciidoctor.org/asciidoc/latest/macros/images/

[cderv]

Sorry I just for mixed up. rst is for restructuredText not asciidoc. This is another hook for asciidoc (hook_plot_asciidoc, here we are talking about hook_plot_rst() above)

I see how I can make rst support the new fig.alt option because it should supports it I guess as you can separated :alt: from caption

[trevorld]

I see how I can make rst support the new fig.alt option because it should supports it I guess as you can separated :alt: from caption

Correct. In a rst "figure" directive you can specify a separate :alt: option from the caption paragraph. Here is the official rst "figure" documentation: https://docutils.sourceforge.io/docs/ref/rst/directives.html#figure e.g.

.. figure:: figure/plot-1.png
    :alt: This is the figure "alt" text option

    This is the figure caption (paragraph)

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