writing an app extension?

[rjkroege]

TL;DR

I wanted to write a Safari Web Extension (in Go obviously.) Like this Swift example code from Apple. Has anybody done this? How did you write the main() for the extension binary?

Long Blither

I know how to convert the main Swift application to Go. But it's completely opaque to me how to create the main() for the extension process. Xcode tells me when breaking at the entry to the NSExtensionRequestHandling implementation (in the extension):

    frame #0: 0x0000000102611780 Sea Creator Extension.debug.dylib`SafariWebExtensionHandler.beginRequest(context=0x000000012b604870) at SafariWebExtensionHandler.swift:13:28
    frame #1: 0x0000000102612534 Sea Creator Extension.debug.dylib`@objc SafariWebExtensionHandler.beginRequest(with:) at <compiler-generated>:0
    frame #2: 0x00000001f302a038 ExtensionFoundation`__112-[EXConcreteExtensionContextVendor _beginRequestWithExtensionItems:listenerEndpoint:withContextUUID:completion:]_block_invoke.102 + 212
    frame #3: 0x00000001f301e274 ExtensionFoundation`-[EXExtensionContextImplementation _willPerformHostCallback:] + 92
    frame #4: 0x00000001f3029c90 ExtensionFoundation`__112-[EXConcreteExtensionContextVendor _beginRequestWithExtensionItems:listenerEndpoint:withContextUUID:completion:]_block_invoke + 928
    frame #5: 0x00000001959428f8 libdispatch.dylib`_dispatch_call_block_and_release + 32
    frame #6: 0x0000000195944658 libdispatch.dylib`_dispatch_client_callout + 20
    frame #7: 0x0000000195952f68 libdispatch.dylib`_dispatch_main_queue_drain + 980
    frame #8: 0x0000000195952b84 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 44
    frame #9: 0x0000000195c1ce60 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 16
    frame #10: 0x0000000195bdca4c CoreFoundation`__CFRunLoopRun + 1996
    frame #11: 0x0000000195bdbbc4 CoreFoundation`CFRunLoopRunSpecific + 588
    frame #12: 0x0000000196d9a808 Foundation`-[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 212
    frame #13: 0x0000000196e12154 Foundation`-[NSRunLoop(NSRunLoop) run] + 64
    frame #14: 0x000000019580e718 libxpc.dylib`_xpc_objc_main + 700
    frame #15: 0x000000019581e824 libxpc.dylib`_xpc_main + 276
    frame #16: 0x000000019580e2b4 libxpc.dylib`xpc_main + 64
    frame #17: 0x0000000196db98e0 Foundation`-[NSXPCListener resume] + 308
    frame #18: 0x00000001a4db8534 PlugInKit`___lldb_unnamed_symbol1080 + 392
    frame #19: 0x00000001a4db83a4 PlugInKit`___lldb_unnamed_symbol1079 + 20
    frame #20: 0x00000001a4db8010 PlugInKit`___lldb_unnamed_symbol1073 + 552
    frame #21: 0x00000001a4db8904 PlugInKit`___lldb_unnamed_symbol1084 + 16
    frame #22: 0x00000001f3025188 ExtensionFoundation`EXExtensionMain + 304
    frame #23: 0x0000000196e1437c Foundation`NSExtensionMain + 204
    frame #24: 0x0000000195774274 dyld`start + 2840

I guess that I'd have to reverse engineer what's going on in PluginKit (frames [24-18]) to setup the XPC service (i.e. register the XPC service so that Safari can find it?) This service is responding to messages from Safari so I'd also have to write / call code to decode the incoming XPC messages (frames [4-2])? I'm questioning the effort-reward ratio here. :-)

[progrium]

I'm also curious to know! Would be a great example.