require the data-latex attribute on fenced Div's again: #1779 (comment)

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
 ================================================================================

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(