Add zero width space to escape emoji shortcodes

Changelog.md

@@ -33,6 +33,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   #130 by @mattt.
 - Fixed file and directory unexpected permissions.
   #146 by @niw.
+- Fixed rendering of colon sequences in function signatures
+  as emoji shortcodes (e.g. `:on:` → 🔛).
+  #149 by @mattt.
 - Fixed declarations for properties without explicit type annotations.
   #150 by @mattt.
 

Sources/swift-doc/Supporting Types/Page.swift

@@ -24,7 +24,13 @@ extension Page {
         let data: Data?
         switch format {
         case .commonmark:
-            data = document.render(format: .commonmark).data(using: .utf8)
+            var text = document.render(format: .commonmark)
+            // Insert U+200B ZERO WIDTH SPACE
+            // to prevent colon sequences from being interpreted as
+            // emoji shortcodes (without wrapping with code element).
+            // See: https://docs.github.com/en/github/writing-on-github/basic-writing-and-formatting-syntax#using-emoji
+            text = text.replacingOccurrences(of: ":", with: ":\u{200B}")
+            data = text.data(using: .utf8)
         case .html:
             data = layout(self).description.data(using: .utf8)
         }