first commit cont.

_extensions/jjallaire/code-visibility/code-visibility.lua

@@ -0,0 +1,51 @@
+
+
+
+-- remove any lines with the hide_line directive.
+function CodeBlock(el)
+  if el.classes:includes('cell-code') then
+    el.text = filter_lines(el.text, function(line)
+      return not line:match("#| ?hide_line%s*$")
+    end)
+    return el
+  end
+end
+
+-- apply filter_stream directive to cells
+function Div(el)
+  if el.classes:includes("cell") then
+    local filters = el.attributes["filter_stream"]
+    if filters then
+      -- process cell-code
+      return pandoc.walk_block(el, {
+        CodeBlock = function(el)
+          -- CodeBlock that isn't `cell-code` is output
+          if not el.classes:includes("cell-code") then
+            for filter in filters:gmatch("[^%s,]+") do
+              el.text = filter_lines(el.text, function(line)
+                return not line:find(filter, 1, true)
+              end)
+            end
+            return el
+          end
+        end
+      })
+      
+    end
+
+  end
+  
+end
+
+function filter_lines(text, filter)
+  local lines = pandoc.List()
+  local code = text .. "\n"
+  for line in code:gmatch("([^\r\n]*)[\r\n]") do
+    if filter(line) then
+      lines:insert(line)
+    end
+  end
+  return table.concat(lines, "\n")
+end
+
+