TypeAlias Formatter

A native macOS app, browser app, and command-line tool that format nested Swift typealiases and demangled type names. All three use the same Core Swift package and preserve private names such as (Modifier in _123ABC)<Style>.

Open the web app · Download the macOS app and CLI

GUI

Paste one typealias or type in the source pane. The output updates as you type. The converter removes a leading typealias Name = declaration before parsing. The app opens with an empty source pane.

• Multiple generic arguments use separate lines and four-space indentation.
• Choose 2 spaces, 4 spaces, 8 spaces, or Tab for indentation. Tab uses one tab character per level and displays at four-space tab stops.
• Single-argument generics stay on one line unless a child needs multiple lines.
• Use Expand generics to expand single-argument generics in text too.
• Text tree shows the formatted type without a declaration header or code fence.
• Select a type in either text pane to highlight its matching range in the other pane. The same selection appears in Graph and survives a mode change.
• Graph shows connected type nodes in argument order. Click a node to highlight its source. Use its arrow to expand or collapse children, and the zoom controls or Fit to inspect the tree. Source selection reveals nodes below collapsed ancestors.
• Graphs initially show two levels of arguments. Expand all shows every node.
• Copy or save Text as plain text (.txt), or the visible Graph as SVG (.svg).
• Use Open to load a UTF-8 .swift, .md, or .txt file.
• The source editor wraps lines by default. Turn off Wrap lines to scroll horizontally. This setting and the indentation choice persist across launches. The output editor scrolls horizontally to preserve deep indentation.

Shortcuts: ⌘O opens a file, ⌘Return formats the input, ⇧⌘C copies the output, and ⌘S saves it.

The formatter checks delimiters, empty arguments, and Markdown fences. It keeps function arrows, tuples, collection types, and type suffixes intact. This is a type layout tool, not a Swift syntax validator. Format one declaration at a time and remove comments first. Input is limited to 200 KB and 128 nesting levels. All formatting runs locally. The native app has no network dependency.

Web app

The web app runs Core as WebAssembly with JavaScriptKit. It supports the same linked source, Text tree, and Graph selection as the native app, plus file import, text/SVG export, zoom, and collapse controls. Input stays in the browser and is never uploaded. Only display preferences persist; each new session starts with empty input.

CLI

Run the CLI with Swift 6 or later, or extract typealias-formatter from the CLI ZIP on GitHub Releases. The CLI does not require Tuist or Icon Composer.

swift run typealias-formatter --help
printf '%s\n' 'typealias Body = Pair<A, Box<B>>' | swift run typealias-formatter
swift run typealias-formatter input.txt --indent tab -o output.txt
swift run typealias-formatter input.txt --format graph -o graph.svg

Option	Behavior
input.txt	Read one UTF-8 file. Omit the path or use - to read stdin.
-o, --output	Write to a file. Omit the path or use - to write to stdout.
--format text	Format plain text. This is the default.
--format graph	Export the full graph as SVG.
--indent 2/4/8/tab	Set text indentation. The default is 4.
--expand-generics	Expand single-argument generics in text output.

The CLI uses the same 200 KB input limit and parsing rules as the GUI. It writes errors to stderr and exits with a nonzero status. It reads and formats the input before writing an output file, so a format error does not overwrite that file. Use -- before an input path that begins with a dash.

Build an optimized CLI binary without generating an Xcode project:

swift build -c release --product typealias-formatter
.build/release/typealias-formatter input.txt

Project structure

Component	Location	Dependencies
TypeAliasFormatterCore Swift package	Packages/TypeAliasFormatterCore	Foundation
TypeAliasFormatterApp target	App	TypeAliasFormatterCore
TypeAliasFormatterCLI target	CLI	TypeAliasFormatterCore, ArgumentParser
TypeAliasFormatterWeb Swift package and browser UI	Web	TypeAliasFormatterCore, JavaScriptKit, CodeMirror

Core contains parsing, text formatting, graph layout, SVG export, UTF-16 source and output mappings, and their tests. Stable node IDs link all three views, including repeated type names and Unicode input. It has no SwiftUI or AppKit dependency. The root Package.swift builds and tests the CLI with the local Core package. Project.swift defines the GUI and CLI Xcode targets; both depend on the Core package through Tuist's Swift Package integration. Tuist reads the dependencies from the root Package.swift, so package paths and versions have one definition. Core sources belong only to the Core package.

The separate Web package keeps JavaScriptKit out of the native app and CLI dependency graph. JavaScript manages the browser UI; Swift handles conversion, selection lookup, graph layout, and SVG generation.

The CLI uses Apple's ArgumentParser. Its license is available in Licenses/SwiftArgumentParser.txt in this repository. The Core package has no third-party dependencies.

Develop

Requires macOS 14 or later, Xcode 26 or later, and Tuist 4 with buildable folder support. The initial project was verified with Tuist 4.206.0 and Xcode 26.6.

tuist install
tuist generate --no-open
open TypeAliasFormatter.xcworkspace

Select the TypeAliasFormatterApp or TypeAliasFormatterCLI scheme to run the corresponding target. Edit Project.swift to change the project. Generated Xcode files and build products are ignored by Git. The GUI and CLI use buildable folders, so new files in those source folders do not need regeneration. Regenerate the workspace after adding Core files or changing target settings. Run tuist install when package dependencies change.

The app icon source is App/Resources/AppIcon.icon. Open it in Icon Composer to edit the four SVG layers, the background, or the material effects. Xcode generates all icon sizes and appearances, including icons for older macOS releases, from this file. See Apple's Icon Composer documentation.

AccentColor in App/Resources/Assets.xcassets defines the app's blue accent for light and dark appearances. The README icon is exported from Icon Composer to Documentation/Images/app-icon-composer.png.

xcodebuild build \
  -workspace TypeAliasFormatter.xcworkspace \
  -scheme TypeAliasFormatterApp \
  -destination 'platform=macOS' \
  -derivedDataPath DerivedData

Run the Core and CLI tests with SwiftPM:

swift test --package-path Packages/TypeAliasFormatterCore
swift test
bash Scripts/test-cli.sh "$(swift build --show-bin-path)/typealias-formatter"

Core fixtures verify the full reference layout after removing its declaration header and code fence. Core tests also cover graph structure, node layout, collapse behavior, SVG output, and source/output mappings. CLI tests cover file output, indentation, input limits, invalid UTF-8, and safe output handling. The integration script checks stdin, stdout, error exits, and SVG output with the built executable.

Web development

Use Swift 6.2.3 with a compatible wasm32-unknown-wasip1 Swift SDK, plus Node.js 24. Install the SDK with setup-swiftwasm or the Swift SDK instructions. Check swift --version and swift sdk list before building.

cd Web
npm ci
PATH="$PWD/node_modules/.bin:$PATH" swift package --swift-sdk <installed-sdk-id> js -c release
npm run build
npm run preview

Open http://127.0.0.1:4173/TypeAliasFormatter/. For browser UI edits, use npm run dev; rebuild the Swift package after changing Core or the Web bridge.

Run the browser tests after building the site:

npx playwright install --only-shell chromium
npm test

The tests load the real WebAssembly module. They check linked selection in both directions, repeated names, collapsed ancestors, Unicode, file import, SVG export, invalid input, persisted settings, and mobile layout.

The Deploy to GitHub Pages workflow tests Core on Linux, builds WebAssembly, and runs the browser tests before deploying. Pushes to main deploy the site; app and CLI releases still require a version tag. Set the repository's Pages source to GitHub Actions when deploying a fork.

Release

Push a tag in vMAJOR.MINOR.PATCH format, such as v0.2.1, to run the Release workflow. It uses Xcode 26.6 and Tuist 4.206.0 to test Core and the CLI, then build the universal GUI and CLI for Apple Silicon and Intel. The app version comes from the tag, and the build number comes from the workflow run number.

The workflow creates a GitHub Release and uploads two assets:

• TypeAliasFormatter-v<version>-macOS.zip contains the GUI app.
• TypeAliasFormatterCLI-v<version>-macOS.zip contains only the universal typealias-formatter executable at the archive root, with no nested ZIP.

The GUI and CLI require macOS 14 or later. Release builds use ad-hoc signing and are not notarized.

For a build check before tagging, run Release manually from the Actions tab and enter the app version. Manual runs store all assets as a workflow artifact and do not publish a GitHub Release.