For pandoc 3.0+, use --split-level when chapter_level is passed in epub_book (#1425)

Author: cderv

NEWS.md

@@ -2,6 +2,8 @@
 
 - Fix an issue with CSL using hanging indent style in `gitbook()` (thanks, @pablobernabeu, #1422).
 
+- Adapt an `epub_book()` internal command-line argument passed to Pandoc for changes from version 3.0 and above (#1425).
+
 - Fix an issue with Pandoc 2.19 not rendering math by default in `epub3` format (#1417).
 
 # CHANGES IN bookdown VERSION 0.33

R/ebook.R

@@ -46,8 +46,9 @@ epub_book = function(
     if (!is.null(cover_image)) c('--epub-cover-image', cover_image),
     if (!is.null(metadata)) c('--epub-metadata', metadata),
     if (!identical(template, 'default')) c('--template', template),
-    if (!missing(chapter_level)) c('--epub-chapter-level', chapter_level),
-    if (rmarkdown::pandoc_available("2.19") && epub_version == "epub3") c("--mathml")
+    if (rmarkdown::pandoc_available('2.19') && epub_version == 'epub3') c('--mathml'),
+    if (!missing(chapter_level))
+      c(if (rmarkdown::pandoc_available('3.0')) '--split-level' else '--epub-chapter-level', chapter_level)
   )
   if (is.null(stylesheet)) css = NULL else {
     css = rmarkdown::pandoc_path_arg(epub_css(stylesheet))