Interfazzle

A wee Swift CLI tool that builds Markdown documentation for a package's public interface from Swift symbol graphs.

Its aimed at package maintainers.

I built this for myself, first and foremost – it scratches my own itches. But it feels kinda useful, even more so now that many of us work with LLMs, and they need to read docs, too. And DocC and its dynamic-page nonsense is the Liquid Glass of documentation. There, I said it.

2025-10-29: Version 1.0 - Now a proper Swift package!

Overview

Interfazzle handles the complete documentation generation pipeline:

1. Validation: Verifies Package.swift exists in the current directory
2. Symbol Graph Generation: Uses Swift's built-in compiler to generate symbol graph JSON files
3. Markdown Conversion: Converts symbol graphs to interface-style Markdown documentation

This approach replaces the old sourcedocs tool, which failed for me when the package includes dependencies with pre-built binaries.

Installation

Install from Source

git clone https://github.com/czottmann/interfazzle.git
cd interfazzle
swift build -c release
cp .build/release/interfazzle /usr/local/bin/

Build Locally

swift build
# Use with: swift run interfazzle

Demo

See Demo folder for a dummy example package containing sources (in Demo/Sources/) and generated documentation (in Demo/docs/).

Usage

Quick Start

Generate all documentation from your Swift package root:

interfazzle generate
# or if not installed:
swift run interfazzle generate

Requirements

• macOS with Swift 6 (tested on Swift 6.0+)
• Must be run from a directory containing Package.swift

Commands

Interfazzle provides three main commands:

generate - Generate Documentation

Generate complete documentation (build + convert) in ./docs/ (default):

interfazzle generate [options]

This will:

1. Verify Package.swift exists in the current directory
2. Parse Package.swift using swift package describe --type json to:
   • Extract module names (your public API)
   • Discover target source paths for README integration
3. Build the project and generate symbol graphs in .build/symbol-graphs/
4. Convert symbol graphs to Markdown files in docs/ with:
   • Interface-style code blocks showing the public API
   • README.md content from module source folders (if present)
   • Intelligently adjusted heading levels for proper hierarchy
   • Automatic filtering to package modules only (excludes dependencies and re-exports)

build - Build Symbol Graphs Only

Build symbol graphs without generating documentation:

interfazzle build [options]

validate - Validate Package

Verify Package.swift exists in current directory:

interfazzle validate

Options

Global Flags

Available for generate and build commands:

• -v, --verbose: Show full swift build output (default: suppressed unless error)
• --be-lenient: On build failure, attempt to continue with existing symbol graphs instead of failing
• -h, --help: Show command-specific help

Generate Command Flags

Additional flags for generate:

• --generate-only: Skip build phase, use existing symbol graphs (useful for quick regeneration)
• --include-reexported: Include symbols from re-exported modules (e.g., from @_exported import)
• --symbol-graphs-dir <dir>: Directory for symbol graphs (default: .build/symbol-graphs)
• --output-dir <dir>: Output directory for documentation (default: docs)
• --modules <list>: Comma-separated list of modules to document (default: all public products)

Build Command Flags

Flags for build:

• --symbol-graphs-dir <dir>: Directory for symbol graphs (default: .build/symbol-graphs)

Note: By default, only modules listed in Package.swift's products (your public API) are documented. Dependency modules are automatically excluded.

Examples

# Show all available commands
interfazzle --help

# Show help for a specific command
interfazzle generate --help

# Basic documentation generation
interfazzle generate

# Skip build, regenerate docs from existing symbol graphs (fast)
interfazzle generate --generate-only

# Show verbose build output for debugging
interfazzle generate --verbose

# Continue with existing symbol graphs if build fails
interfazzle generate --be-lenient

# Include re-exported symbols (e.g., from @_exported import)
interfazzle generate --include-reexported

# Document specific modules only
interfazzle generate --modules "ModuleF,ModuleC,ModuleK,ModuleN,ModuleZ,ModuleS"

# Use custom directories
interfazzle generate --symbol-graphs-dir .build/symbols --output-dir output-docs

# Combine flags
interfazzle generate --verbose --be-lenient
interfazzle generate --include-reexported --verbose

# Custom directories with specific modules
interfazzle generate --symbol-graphs-dir custom-graphs --output-dir custom-docs --modules "MyModule"

# Just build symbol graphs without generating docs
interfazzle build --verbose

# Build to custom directory
interfazzle build --symbol-graphs-dir custom-graphs

# Validate package before other operations
interfazzle validate

Output Format

Each module generates a single Markdown file with interface-style code blocks showing the complete public API in Swift syntax, similar to how Xcode shows generated interfaces.

• H2 heading with module name
• Optional README content (with adjusted heading levels)
• H3 heading: "Public interface"
• Swift code blocks with complete interface declarations
• Documentation comments as triple-slash syntax above each symbol

Structure

• H2: Module name (## Module \ModuleName``)
• Optional: README content from module source folder (e.g., Sources/ModuleName/README.md)
  • Headings automatically adjusted so the highest level becomes H3
  • Maintains relative hierarchy of all headings
• H3: "Public interface" heading
• Code blocks: Swift interface declarations grouped by type
  • Protocols → Structs → Classes → Enums → Extensions → Macros → Functions
  • Nested types rendered within parent declarations
  • Documentation comments as triple-slash (///) comments above declarations

README Integration

If a module folder contains a README.md file, its content is automatically included after the module heading. The script:

1. Removes duplicate module name headings (e.g., # ModuleName)
2. Adjusts heading levels intelligently:
   • Finds the highest heading level in the README (e.g., ## = level 2)
   • Shifts it to H3 to fit under the module's H2
   • Applies the same shift to all other headings to maintain hierarchy
3. Example: README with ## and ### → becomes ### and #### in output

Architecture

Interfazzle is now a proper Swift package with modular architecture:

Package Structure

• Interfazzle - Core library module with all documentation generation logic

  • Models/ - Data structures (Config, SymbolGraph, PackageDescription)
  • Core/ - Core logic (PackageValidator, SymbolGraphBuilder, ModuleExtractor, PackageInfoLoader)
  • Generation/ - Documentation generation (DocumentationGenerator, SymbolSorter, DeclarationFormatter, MarkdownFormatter)

• InterfazzleCLI - Executable module with SwiftCLI-based command-line interface

  • Commands/ - Command implementations (GenerateCommand, BuildCommand, ValidateCommand)
  • Uses SwiftCLI for argument parsing and help generation

Features

• Validation: Checks for Package.swift in current directory
• Orchestration: Builds symbol graphs and generates documentation in one command
• Filtering: Automatically filters to public product modules (excludes dependencies and re-exports)
• Multiple Commands: Separate commands for generate, build, and validate
• Customization: Optional custom directories and module filtering
• README Integration: Automatically includes README.md from module source folders
• Heading Adjustment: Intelligently adjusts README heading levels to maintain hierarchy
• Interface-style Output: Generates code blocks like Xcode's generated interfaces
• Symbol Grouping: Organizes by type (protocols → structs → classes → enums → extensions)
• Nested Types: Handles nested types with proper indentation
• Protocol Consolidation: Shows all protocol conformances in main class declarations
• Doc Comments: Renders documentation comments as triple-slash (///) syntax
• Error Handling: Clear error messages with appropriate exit codes

Exit Codes

• 0: Success
• 1: Validation error (e.g., Package.swift not found)
• 2: Build error (when not using --be-lenient)
• 3: Documentation generation error

Legacy Script

The original monolithic interfazzle.swift script is preserved as interfazzle.legacy.swift for reference purposes. It should not be used or modified.

How It Works

Symbol Graphs

Swift's compiler can emit "symbol graphs" - JSON files containing all public API information:

• Types (classes, structs, enums, protocols)
• Properties and methods
• Documentation comments
• Declaration signatures
• Relationships between symbols

Conversion Process

The DocumentationGenerator module's Markdown generation phase:

1. Reads symbol graph JSON files from .build/symbol-graphs/
2. Filters to public product modules by default (excludes dependencies)
3. Filters to public API symbols (public and open access levels, excludes internal/private/synthesized)
4. Groups symbols by:
   • Type (protocols, structs, classes, enums, extensions)
   • Nesting (properties, methods, etc. under parent types)
5. Generates one Markdown file per module with all content consolidated:
   • ModuleName.md containing all symbols for that module
   • Interface-style code blocks showing the complete public API
   • Optional README content with intelligently adjusted heading levels

Why Not SourceDocs?

SourceDocs failed for me on projects:

1. It uses SourceKit, which crashes when dependencies include pre-built binaries
2. Symbol graphs are compiler-generated, so they handle all valid Swift packages
3. Symbol graphs are the official way Apple recommends for documentation tooling

The above conclusions might be wrong, I'm still a noob in a lot of regards when it comes to Swift.

Differences from SourceDocs Output

The generated documentation differs from SourceDocs in structure and format:

1. Interface-style code blocks: Shows complete Swift interface in code blocks (like Xcode's generated interfaces) instead of individual sections per symbol
2. Consolidated files: One ModuleName.md file per module instead of folder-per-module with multiple files
3. Minimal headings: Just module name (H2) and "Public interface" (H3), with all API in code blocks
4. README integration: Automatically includes README.md from module source folders with intelligent heading adjustment
5. Protocol consolidation: Shows all protocol conformances (including from extensions) in the main class declaration
6. Nested type rendering: Nested types appear within their parent declarations, maintaining proper Swift syntax

The interface-style format is more compact, easier to read, and better reflects how developers actually view APIs in Xcode.

Future Improvements

Potential enhancements:

• Generate cross-reference links between types
• Add availability information (iOS 16+, macOS 13+, etc.) to declarations
• Support for Linux and other platforms

Troubleshooting

"Cannot read symbol graphs directory"

Run interfazzle generate without --generate-only to build symbol graphs first, or use the build command:

interfazzle build

Or manually build them:

swift build -Xswiftc -emit-symbol-graph -Xswiftc -emit-symbol-graph-dir -Xswiftc .build/symbol-graphs

"Package.swift not found in current directory"

All commands must be run from the root of a Swift package (where Package.swift is located). Use interfazzle validate to check.

Missing symbols in output

Only public API symbols (public and open access levels) are documented. Internal/private/fileprivate symbols are intentionally excluded.

README not being included

The script looks for README.md in the target's source path as defined in Package.swift. If your README isn't being included:

1. Verify the file is named exactly README.md (case-sensitive)
2. Check it's in the module's source directory (e.g., Sources/ModuleName/README.md)
3. Verify the target path in Package.swift matches where the README is located

Formatting issues

The script uses Swift's declaration fragments directly. If formatting looks odd, check the symbol graph JSON to see what the compiler emits.

Build errors blocking documentation generation

Use --be-lenient to generate docs from existing symbol graphs even if the build fails:

interfazzle generate --be-lenient

Dependency modules appearing in output

This shouldn't happen with the current version. Interfazzle automatically filters to only public product modules. If you see dependency docs being generated, please report it as a bug.

Regenerating docs quickly after edits

Use --generate-only to skip the build phase and regenerate docs from existing symbol graphs:

interfazzle generate --generate-only

This is much faster when you've only changed documentation comments or README files.

Re-exported symbols missing from output

By default, Interfazzle filters out symbols from re-exported modules (e.g., from @_exported import) to keep documentation focused on your package's own API. If you need to include these symbols:

interfazzle generate --include-reexported

This will include symbols from frameworks like OSLog that are re-exported using @_exported import.

Author

Carlo Zottmann, carlo@zottmann.dev, https://c.zottmann.dev, https://github.com/czottmann

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