macOS Markdown File Association

March 29, 2026 · View on GitHub

Overview

Ferrite’s macOS .app bundle declares the standard Markdown UTI (net.daringfireball.markdown) so Finder can offer Open With → Ferrite and users can set Ferrite as the default app for .md and related extensions. This uses both imported type declarations and document types merged into Info.plist at bundle time.

Key Files

  • assets/macos/info_plist_ext.xml — Plist fragment merged by cargo-bundle: UTImportedTypeDeclarations for the Markdown UTI, plus CFBundleDocumentTypes for editor role and extensions.
  • Cargo.toml — [package.metadata.bundle] → osx_info_plist_exts = ["assets/macos/info_plist_ext.xml"].
  • .github/workflows/release.yml — macOS release jobs run cargo bundle --release (Intel uses --target x86_64-apple-darwin); the merged plist ships inside Ferrite.app in DMG/tar artifacts.

Implementation Details

  • UTI: net.daringfireball.markdown (reference: Daring Fireball Markdown), conforming to public.plain-text.
  • Extensions: md, markdown, mdown, mkd, mkdn.
  • UTImportedTypeDeclarations: Imports the UTI so the system knows how .md files relate to the declared type when resolving handlers.
  • CFBundleDocumentTypes: Registers Ferrite as an editor for that UTI (and related content types), alongside JSON, YAML, TOML, and plain text entries in the same fragment.

CI does not patch Info.plist separately; cargo-bundle reads osx_info_plist_exts from Cargo.toml on every build.

Dependencies Used

  • cargo-bundle — Produces Ferrite.app and merges info_plist_ext.xml into Contents/Info.plist.

Usage

Verify the merged plist (macOS)

After a local bundle build:

cargo install cargo-bundle   # once
cargo bundle --release
plutil -p target/release/bundle/osx/Ferrite.app/Contents/Info.plist | head -80

Confirm entries for UTImportedTypeDeclarations / CFBundleDocumentTypes and net.daringfireball.markdown.

Manual UX check

  1. Install or run Ferrite.app from a release DMG or local cargo bundle.
  2. In Finder, right-click a .md file → Open With — Ferrite should appear.
  3. Optionally set as default — double-click should open Ferrite.