Empty lines are not formatted correctly in verbatim text

[s-fleck]

Empty lines in verbatim / preformatted text that render correctly inside the R documentation
produce an indent of the following line, instead of an empty line.

So this:

#' ```
#' foo
#' 
#' bar
#' ```

renders as this:

foo
   bar

Example from another r-lib package: processx

[kevinushey]

I think this bug ultimately comes down to parse_section() treating the code chunk as multiple paragraphs:

x <- structure(list(
  structure("\n", class = c("TEXT", "tag")),
  structure("Here is a code section.", class = c("TEXT", "tag")),
  structure(
    list(
      structure("Line 1\n", class = c("VERB", "tag")),
      structure("\n", class = c("VERB", "tag")),
      structure("Line 2\n", class = c("VERB", "tag")),
      structure("\n", class = c("VERB", "tag")),
      structure("Line 3\n", class = c("VERB", "tag"))
    ),
    class = c("tag_preformatted", "tag")
  ),
  structure("\n", class = c("TEXT", "tag"))
),
class = c("tag_details", "tag"))

pkgdown:::parse_section(x, "Details")
#> $title
#> [1] "Details"
#> 
#> $contents
#> [1] "<p>Here is a code section.</p><pre>Line 1"
#> [2] "Line 2"                                   
#> [3] "Line 3\n</pre>"

^{Created on 2019-04-09 by the reprex package (v0.2.1)}

I think parse_section() needs to better understand tag_preformatted blocks.

[jayhesselberth]

The newline stripping done by split_at_linebreaks() in parse_section() needs to be moved into flatten_para(), where block_tags (e.g. tag_preformatted) are still available.