`ansi_html()` bug when strings with the same style have been pasted together

[trevorld]

I'm observing an error with ansi_html() when strings with the same styles have been pasted together. An example:

library("cli")
asf <- combine_ansi_styles(bg_blue, col_br_yellow)
s <- paste(rep_len(asf(" "), 10L), collapse = "")
h_cli <- ansi_html(s)
print(h_cli)

[1] "<span class=\"ansi ansi-color-3 ansi-bg-color-4\"> </span>         "

Note only the first space is styled with the correct background color and the remaining nine spaces are unstyled. In contrast I believe the right output should instead be:

[1] "<span class=\"ansi ansi-color-3 ansi-bg-color-4\">          </span>"

(note the different placement of the </span>). In contrast fansi::sgr_to_html() seems to correctly preserve a style for all ten spaces:

h_fansi <- fansi::sgr_to_html(s)
print(h_fansi)

[1] "<span style='color: #FFFF55; background-color: #0000BB;'>          </span>"

[trevorld]

A possible test case for tests/testthat/test-ansi-html.R:

# https://github.com/r-lib/cli/issues/752
expect_equal(
  ansi_html("\033[91mR\033[39m\033[91mR\033[39m"),
  "<span class=\"ansi ansi-color-1\">RR</span>"
)

where

> paste0(col_br_red("R"), col_br_red("R"))
[1] "\033[91mR\033[39m\033[91mR\033[39m"