From b2cff70c523b1bd6a7269fc8c28ee9ca9f51c71a Mon Sep 17 00:00:00 2001
From: Yihui Xie <xie@yihui.name>
Date: Mon, 29 Jun 2020 15:53:31 -0500
Subject: [PATCH] require the data-latex attribute on fenced Div's again:
 https://github.com/rstudio/rmarkdown/issues/1779#issuecomment-647184984

---
 NEWS.md                    |  2 ++
 inst/rmd/lua/latex-div.lua | 10 ++++------
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 0c9bfb69c0..a7fb409d4c 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,6 +1,8 @@
 rmarkdown 2.4
 ================================================================================
 
+- Since **rmarkdown** 1.16, Pandoc's fenced `Div`'s are converted to LaTeX environments when the output format is LaTeX, e.g., `::: {.center data-latex=""}` is converted to `\begin{center}`. The attribute `data-latex` of the `Div` was mandatory, even if it is empty. In **rmarkdown** 2.2, we silently drop this requirement, which means `::: {.center}` is converted to `\begin{center}`. This turns out to be a bad idea, because users have no control over which Div's to be converted to LaTeX environments. Previously, they could opt-in by the `data-latex` attribute, but with **rmarkdown** 2.3, all Div's are converted to LaTeX environments unconditionally. What's more, this change led to bugs like https://stackoverflow.com/q/62340425/559676 and https://github.com/rstudio/bookdown/issues/883. Therefore the `data-latex` attribute became mandatory again in this version. If the LaTeX environment does not need arguments, you may use `data-latex=""`.
+
 
 rmarkdown 2.3
 ================================================================================
diff --git a/inst/rmd/lua/latex-div.lua b/inst/rmd/lua/latex-div.lua
index ab4bc032f9..cc80f7c054 100644
--- a/inst/rmd/lua/latex-div.lua
+++ b/inst/rmd/lua/latex-div.lua
@@ -6,13 +6,11 @@
 
 Div = function (div)
   local options = div.attributes['data-latex']
+  if options == nil then return nil end
 
-  -- if the output format is not latex, the object is left unchanged
+  -- if the output format is not latex, remove the data-latex attr and return
   if FORMAT ~= 'latex' and FORMAT ~= 'beamer' then
-    -- if options has been set for latex, unset for other output
-    if options then
-      div.attributes['data-latex'] = nil
-    end
+    div.attributes['data-latex'] = nil
     return div
   end
 
@@ -23,7 +21,7 @@ Div = function (div)
   -- insert raw latex before content
   table.insert(
     div.content, 1,
-    pandoc.RawBlock('tex', '\\begin' .. '{' .. env .. '}' .. (options or ""))
+    pandoc.RawBlock('tex', '\\begin' .. '{' .. env .. '}' .. options)
   )
   -- insert raw latex after content
   table.insert(