render double-bracketed wiki links, roughly in Obsidian style

fixwikilinks.lua

@@ -0,0 +1,26 @@
+-- Pandoc's wikilinks_title_after_pipe extension makes a start at linking
+-- [[bracketed wiki links]]. This lua filter finishes the job and tries to
+-- mimic Obsidian's wiki linking, by
+-- - either hyphen-replacing or dropping all problem characters in the uri
+-- - adding ".html" to the uri path
+-- - preserving the uri fragment if any
+-- - lower-casing the uri fragment
+
+function Link(elem)
+   if elem.title == "wikilink" then
+      t = elem.target .. "#"
+      t = string.gsub(t, " ", "-")
+      t = string.gsub(t, "'", "")
+      path, frag = string.match(t, "([^#]*)#([^#]*)")
+      t = path
+      if string.len(path) > 0 then
+         t = t .. ".html"
+      end
+      if string.len(frag) > 0 then
+         frag = pandoc.text.lower(frag)
+         t = t .. "#" .. frag
+      end
+      elem.target = t
+   end
+   return elem
+end