fix disappearance of figure captions when a chunk generates multiple figures continuously

NEWS.md

@@ -4,6 +4,8 @@
 
 - The chunk option `collapse = TRUE` now works as expected when the chunk option `attr.*` or `class.*` is provided. By this change, The chunk option `collapse = TRUE` forces `attr.*` and `class.*` be `NULL` except for the chunk options `attr.source` and `class.source` (thanks, @aosavi @cderv @atusy, #1902 #1906).
 
+- Captions disappeared when a chunk generates multiple figures continuously (thanks, @atusy, #1760)
+
 # CHANGES IN knitr VERSION 1.30
 
 ## NEW FEATURES

R/hooks-md.R

@@ -3,25 +3,26 @@
 hook_plot_md = function(x, options) {
   # if not using R Markdown v2 or output is HTML, just return v1 output
   if (is.null(to <- pandoc_to()) || is_html_output(to))
-    return(hook_plot_md_base(x, options))
+    return(append_blank_lines(hook_plot_md_base(x, options), options))
   if ((options$fig.show == 'animate' || is_tikz_dev(options)) && is_latex_output())
     return(hook_plot_tex(x, options))
+
   office_output = to %in% c('docx', 'pptx', 'rtf', 'odt')
   if (need_special_plot_hook(options)) {
     if (is_latex_output()) {
       # Pandoc < 1.13 does not support \caption[]{} so suppress short caption
       if (is.null(options$fig.scap)) options$fig.scap = NA
-      return(hook_plot_tex(x, options))
+      return(append_blank_lines(hook_plot_tex(x, options), options))
     }
     if (office_output) {
       if (options$fig.align != 'default') {
         warning('Chunk options fig.align is not supported for ', to, ' output')
         options$fig.align = 'default'
       }
-      return(hook_plot_md_pandoc(x, options))
+      return(append_blank_lines(hook_plot_md_pandoc(x, options), options))
     }
   }
-  hook_plot_md_base(x, options)
+  append_blank_lines(hook_plot_md_base(x, options), options)
 }
 
 # decide if the markdown plot hook is not enough and needs special hooks like
@@ -114,6 +115,16 @@ css_text_align = function(align) {
   if (align == 'default') '' else sprintf(' style="text-align: %s"', align)
 }
 
+append_blank_lines = function(x, options) {
+  if (
+    (!identical(options$echo, FALSE) && options$fig.show != 'hold') ||
+    is.null(options$fig.cap) || options$fig.num == options$fig.cur
+  ) {
+    return(x)
+  }
+  paste0(x, "\n\n")
+}
+
 # turn a class string "a b" to c(".a", ".b") for Pandoc fenced code blocks
 block_class = function(x) {
   if (length(x) > 0) gsub('^[.]*', '.', unlist(strsplit(x, '\\s+')))

tests/testit/test-hooks-md.R

@@ -67,8 +67,15 @@ x = "1.png"
 w = h = 1
 ex = "style='margin: 0;'"
 cap = "foo"
-opt <- function(w = NULL, h =NULL, ex = NULL, cap = NULL, show = 'asis', ...) {
-  list(out.width = w, out.height = h, out.extra = ex, fig.cap = cap, fig.show = show, ...)
+align = 'left'
+link = 'https://example.com'
+opt <- function(
+  w = NULL, h =NULL, ex = NULL, align = 'default', cap = NULL, show = 'asis', ...
+) {
+  list(
+    out.width = w, out.height = h, out.extra = ex,
+    fig.align = align, fig.cap = cap, fig.show = show,...
+  )
 }
 
 assert("Include a plot by pandoc md", {
@@ -80,3 +87,67 @@ assert("Include a plot by pandoc md", {
   (hook_plot_md_pandoc(x, opt(w = w, cap = cap, ex = ex)) %==%
     sprintf("![%s](1.png){width=%s %s}", cap, w, ex))
 })
+
+hook = hook_plot_md_base
+assert("Include a plot in variety of formats with hook_plot_md_base", {
+  # width, height, and extra are null, and align is default
+  (hook(x, opt()) %==% "![](1.png)")
+  (hook(x, opt(cap = cap)) %==% sprintf("![%s](1.png)", cap))
+  (hook(x, opt(fig.link = link)) %==% sprintf("[![](1.png)](%s)", link))
+  opts_knit$set(rmarkdown.pandoc.to = 'latex')
+  (hook(x, opt(cap = '')) %==% "![](1.png)<!-- --> ")
+  opts_knit$set(rmarkdown.pandoc.to = 'html')
+  (hook(x, opt(cap = '')) %==% "![](1.png)<!-- -->")
+  # html output with caption or width
+  (hook(x, opt(align = align, cap = cap)) %==%
+      sprintf('<div class="figure" style="text-align: %s">\n<img src="1.png" alt="%s"  />\n<p class="caption">%s</p>\n</div>', align, cap, cap))
+  ## add link
+  (hook(x, opt(w = w, cap = cap, fig.link = link)) %==%
+      sprintf('<div class="figure">\n<a href="%s" target="_blank"><img src="1.png" alt="%s" width="%s" /></a>\n<p class="caption">%s</p>\n</div>', link, cap, w, cap))
+  ## fig.caption is TRUE
+  (hook(x, opt(w = w, cap = cap, fig.topcaption = TRUE)) %==%
+      sprintf('<div class="figure">\n<p class="caption">%s</p><img src="1.png" alt="%s" width="%s" /></div>', cap, cap, w))
+  ## plot1 is FALSE
+  (hook(x, opt(w = w, cap = cap, show = 'hold', fig.cur = 2, fig.num = 2)) %==%
+      sprintf('<img src="1.png" alt="%s" width="%s" />\n<p class="caption">%s</p>\n</div>', cap, w, cap))
+  ## plot2 is FALSE
+  (hook(x, opt(w = w, cap = cap, show = 'hold', fig.cur = 1, fig.num = 2)) %==%
+      sprintf('<div class="figure">\n<img src="1.png" alt="%s" width="%s" />', cap, w, cap))
+  # else
+  opts_knit$restore()
+  (hook(x, opt(align = 'center')) %==% '<img src="1.png" style="display: block; margin: auto;" />')
+})
+
+hook <- hook_plot_md
+assert('Check if hook_plot_md passes arguments to sub-functions', {
+  opts_knit$set(rmarkdown.pandoc.to = 'html')
+  (hook(x, opt()) %==% hook_plot_md_base(x, opt()))
+
+  opts_knit$set(rmarkdown.pandoc.to = 'latex')
+  o = opt(w = w)
+  (hook(x, o) %==% hook_plot_tex(x, o))
+
+  opts_knit$set(rmarkdown.pandoc.to = 'docx')
+  (hook(x, o) %==% hook_plot_md_pandoc(x, o))
+
+  opts_knit$set(rmarkdown.pandoc.to = 'markdown')
+  (hook(x, opt()) %==% hook_plot_md_base(x, opt()))
+  (hook(x, o) %==% hook_plot_md_base(x, o))
+})
+
+assert('Conditionally append blank lines to figures so that figure captions are displayed correctly', {
+  # Append when echo is FALSE or fig.show is hold and the current figure is not the last one
+  (append_blank_lines('a', list(echo = FALSE, fig.cap = cap, fig.num = 3, fig.cur = 1)) %==% 'a\n\n')
+  (append_blank_lines('a', list(fig.show = 'hold', fig.cap = cap, fig.num = 3, fig.cur = 1)) %==% 'a\n\n')
+
+  # Do not append when
+  ## echo is not FALSE
+  (append_blank_lines('', list(echo = TRUE)) %==% '')
+  ## fig.show is not hold
+  (append_blank_lines('', list(echo = FALSE, fig.show = 'asis')) %==% '')
+  ## fig.cap is NULL
+  (append_blank_lines('', list(echo = FALSE, fig.cap = NULL)) %==% '')
+  ## fig.num is equal to fig.cur
+  (append_blank_lines('', list(echo = FALSE, fig.cap = cap, fig.num = 1, fig.cur = 1)) %==% '')
+})
+