Style invalid bracket links (grey them out)

_plugins/bidirectional_links_generator.rb

@@ -18,6 +18,19 @@ class BidirectionalLinksGenerator < Jekyll::Generator
           "<a class='internal-link' href='#{note_potentially_linked_to.url}'>#{note_potentially_linked_to.data['title']}</a>"
         )
       end
+
+      # At this point, all remaining double-bracket-wrapped words are
+      # pointing to non-existing pages, so let's turn them into disabled
+      # links by greying them out and changing the cursor
+      current_note.content = current_note.content.gsub(
+        /\[\[?(.*)\]\]/i, # match on the remaining double-bracket links
+        <<~HTML.chomp     # replace with this HTML (\\1 is what was inside the brackets)
+          <span title='There is no note that matches this title.' class='invalid-link'>
+            <span class='invalid-link-brackets'>[[</span>
+            \\1
+            <span class='invalid-link-brackets'>]]</span></span>
+        HTML
+      )
     end
 
     # Identify note backlinks and add them to each note

_sass/_style.scss

@@ -128,3 +128,15 @@ code {
   padding: 0.1em 0.2em;
   border-radius: 4px;
 }
+
+.invalid-link {
+  color: #444444;
+  cursor: help;
+  background: #fafafa;
+  padding: 0 0.1em;
+}
+
+.invalid-link-brackets {
+  color: #ccc;
+  cursor: help;
+}