Simple bootstrap script for prototyping SwiftUI apps without an Xcode project.

swift-run.py

#!/usr/bin/env python3

"""
Simple bootstrap script for quickly prototyping
Swift-based macOS applications.

usage: swift-run.py [-h] [-c SWIFT_COMPILER] [-a ARGS] [-m MAIN] [-s SAVE]
                    file [file ...]

positional arguments:
  file                  list of files to run

optional arguments:
  -h, --help            show this help message and exit
  -c SWIFT_COMPILER, --swift-compiler SWIFT_COMPILER
                        swift compiler path (default: swift)
  -a ARGS, --args ARGS  swift compiler args (default: )
  -m MAIN, --main MAIN  main SwiftUI view (default:
                        ContentView().frame(maxWidth: .infinity, maxHeight:
                        .infinity))
  -s SAVE, --save SAVE  saves the joined swift files + boilerplate to this
                        file (default: )

"""

import argparse
import os
import subprocess
import tempfile
from typing import List

DEFAULTS = {
    "main_view": "ContentView().frame(maxWidth: .infinity, maxHeight: .infinity)",
    "swift_args": "",
    "swift_exec": "swift",
    "window": {
        "width": 480,
        "height": 480,
        "style_titled": True,
        "style_closable": True,
        "style_miniaturizable": True,
        "style_resizable": True,
        "style_fullSizeContentView": True,
    },
}


def join_files(files: List[str], boilerplate: str = ""):
    all_text = ""

    for file in files:
        with open(file, "r") as f:
            all_text += f.read() + "\n\n"

    all_text += boilerplate
    return all_text


def exec_text(text: str, swift_exec: str = "", swift_args: str = "", script_out: str = None):
    with tempfile.TemporaryDirectory() as tmp_dir:
        if script_out is None or script_out.strip() == "":
            script_out = os.path.join(tmp_dir, "main.swift")
        
        with open(script_out, "w") as f:
            f.write(text)

        cmd = f"{swift_exec} {swift_args} {script_out}"
        print(cmd)

        subprocess.run(
            cmd.split(),
            check=True,
            capture_output=True,
        )


def get_boilerplate(main_view: str = "ContentView()"):
    return (
        """
// Run any SwiftUI view as a Mac app.

import Cocoa
import SwiftUI

NSApplication.shared.run {
    """
        + main_view
        + """
}

extension NSApplication {
    public func run<V: View>(@ViewBuilder view: () -> V) {
        let appDelegate = AppDelegate(view())
        NSApp.setActivationPolicy(.regular)
        mainMenu = customMenu
        delegate = appDelegate
        run()
    }
}

// Inspired by https://www.cocoawithlove.com/2010/09/minimalist-cocoa-programming.html

extension NSApplication {
    var customMenu: NSMenu {
        let appMenu = NSMenuItem()
        appMenu.submenu = NSMenu()
        let appName = ProcessInfo.processInfo.processName
        appMenu.submenu?.addItem(NSMenuItem(title: "About \(appName)", action: #selector(NSApplication.orderFrontStandardAboutPanel(_:)), keyEquivalent: ""))
        appMenu.submenu?.addItem(NSMenuItem.separator())
        let services = NSMenuItem(title: "Services", action: nil, keyEquivalent: "")
        self.servicesMenu = NSMenu()
        services.submenu = self.servicesMenu
        appMenu.submenu?.addItem(services)
        appMenu.submenu?.addItem(NSMenuItem.separator())
        appMenu.submenu?.addItem(NSMenuItem(title: "Hide \(appName)", action: #selector(NSApplication.hide(_:)), keyEquivalent: "h"))
        let hideOthers = NSMenuItem(title: "Hide Others", action: #selector(NSApplication.hideOtherApplications(_:)), keyEquivalent: "h")
        hideOthers.keyEquivalentModifierMask = [.command, .option]
        appMenu.submenu?.addItem(hideOthers)
        appMenu.submenu?.addItem(NSMenuItem(title: "Show All", action: #selector(NSApplication.unhideAllApplications(_:)), keyEquivalent: ""))
        appMenu.submenu?.addItem(NSMenuItem.separator())
        appMenu.submenu?.addItem(NSMenuItem(title: "Quit \(appName)", action: #selector(NSApplication.terminate(_:)), keyEquivalent: "q"))
        
        let windowMenu = NSMenuItem()
        windowMenu.submenu = NSMenu(title: "Window")
        windowMenu.submenu?.addItem(NSMenuItem(title: "Minmize", action: #selector(NSWindow.miniaturize(_:)), keyEquivalent: "m"))
        windowMenu.submenu?.addItem(NSMenuItem(title: "Zoom", action: #selector(NSWindow.performZoom(_:)), keyEquivalent: ""))
        windowMenu.submenu?.addItem(NSMenuItem.separator())
        windowMenu.submenu?.addItem(NSMenuItem(title: "Show All", action: #selector(NSApplication.arrangeInFront(_:)), keyEquivalent: "m"))
        
        let mainMenu = NSMenu(title: "Main Menu")
        mainMenu.addItem(appMenu)
        mainMenu.addItem(windowMenu)
        return mainMenu
    }
}

class AppDelegate<V: View>: NSObject, NSApplicationDelegate, NSWindowDelegate {
    init(_ contentView: V) {
        self.contentView = contentView
        
    }
    var window: NSWindow!
    var hostingView: NSView?
    var contentView: V
    
    func applicationDidFinishLaunching(_ notification: Notification) {
        window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered, defer: false)
        window.center()
        window.setFrameAutosaveName("Main Window")
        hostingView = NSHostingView(rootView: contentView)
        window.contentView = hostingView
        window.makeKeyAndOrderFront(nil)
        window.delegate = self
        NSApp.activate(ignoringOtherApps: true)
    }
}
"""
    )


if __name__ == "__main__":
    parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument(
        "files", metavar="file", type=str, nargs="+", help="list of files to run"
    )
    parser.add_argument(
        "-c",
        "--swift-compiler",
        help="swift compiler path",
        type=str,
        default=DEFAULTS["swift_exec"],
    )
    parser.add_argument(
        "-a",
        "--args",
        help="swift compiler args",
        type=str,
        default=DEFAULTS["swift_args"],
    )
    parser.add_argument(
        "-m",
        "--main",
        help="main SwiftUI view",
        type=str,
        default=DEFAULTS["main_view"],
    )
    parser.add_argument(
        "-s",
        "--save",
        help="saves the joined swift files + boilerplate to this file",
        type=str,
        default="",
    )

    args = parser.parse_args()
    print(args)

    exec_text(
        join_files(args.files, boilerplate=get_boilerplate(args.main)),
        swift_exec=args.swift_compiler,
        swift_args=args.args,
        script_out=args.save
    )