another request from #1602: use the fold-hide class to hide the code blocks initially (#1798)

Author: atusy

NEWS.md

@@ -5,6 +5,8 @@ rmarkdown 2.2
 
 - Floating TOC can now distinguish upper/lower-cases (thanks, @atusy, #1783).
 
+- When `code_folding='show'` for the output format `html_document`, code blocks can be individually hidden initially by specifying the chunk option `class.source='fold-hide'` (thanks, @atusy, #1798).
+
 
 rmarkdown 2.1
 ================================================================================

inst/rmd/h/navigation-1.1/codefolding.js

@@ -22,8 +22,8 @@ window.initializeCodeFolding = function(show) {
 
     // create a collapsable div to wrap the code in
     var div = $('<div class="collapse r-code-collapse"></div>');
-    if (show || $(this)[0].classList.contains('fold-show'))
-      div.addClass('in');
+    show = (show || $(this).hasClass('fold-show')) && !$(this).hasClass('fold-hide');
+    if (show) div.addClass('in');
     var id = 'rcode-643E0F36' + currentIndex++;
     div.attr('id', id);
     $(this).before(div);