title: How to troubleshoot when Safari App Extension not appear in Safari Preferences?
body: <p>I'm developing a Safari App Extension. Previously it worked fine. When I run the project in Xcode, and enable <em>Allow Unsigned Extensions</em> in Safari, I can see my extension in <em>Safari Preferences -> Extensions</em> page. </p>
  
  <p>After I merged code with one of my team member, suddenly the Extension cannot get installed.</p>
  
  <p>I have tried:</p>
  
  <ul>
  <li>Clean the build folder in Xcode, and run again. But no luck.</li>
  <li>Restart Xcode doesn't help either.</li>
  <li>Use command <code>pluginkit -mAvvv -p com.apple.Safari.extension</code> to check installed Safari extensions list. My extension is not in the list.</li>
  </ul>
  
  <p>There are some errors in Xcode output, but I can't link them with the issue I'm facing:</p>
  
  <pre><code>objc[49476]: Class AMSupportURLConnectionDelegate is implemented in both /System/Library/PrivateFrameworks/EmbeddedOSInstall.framework/Versions/A/EmbeddedOSInstall (0x7fff9a2aa748) and /System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x108db2600). One of the two will be used. Which one is undefined.
  objc[49476]: Class AMSupportURLSession is implemented in both /System/Library/PrivateFrameworks/OSPersonalization.framework/Versions/A/OSPersonalization (0x7fff9b5d49f0) and /System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x108db2650). One of the two will be used. Which one is undefined.
  2018-12-13 16:25:46.003099+0800 Safari[49476:1264277] Could not connect action, target class SecurityPreferences does not respond to -toggleJavaScriptCanOpenWindows:
  2018-12-13 16:25:46.163130+0800 Safari[49476:1264277] AssertMacros: 0 (value = 0x0),  file: /BuildRoot/Library/Caches/com.apple.xbs/Sources/BiometricKit/BiometricKit-75.71.1/BiometricKit/BiometricKitXPCClient.m, line: 75
  2018-12-13 16:25:46.163219+0800 Safari[49476:1264277] AssertMacros: 0 (value = 0x0),  file: /BuildRoot/Library/Caches/com.apple.xbs/Sources/BiometricKit/BiometricKit-75.71.1/BiometricKit/BiometricKitXPCClient.m, line: 396
  2018-12-13 16:25:46.163465+0800 Safari[49476:1264277] [Framework-Internal-Legacy] AssertMacros: _xpcClient (value = 0x0),  file: /BuildRoot/Library/Caches/com.apple.xbs/Sources/BiometricKit/BiometricKit-75.71.1/BiometricKit/BiometricKit.m, line: 137
  2018-12-13 16:25:47.060959+0800 Safari[49476:1264368] [RemotePlistController] The downloaded plist could not be loaded: Error Domain=NSCocoaErrorDomain Code=260 "The file couldn’t be opened because it doesn’t exist."
  2018-12-13 16:25:47.128105+0800 Safari[49476:1264277] Scheduling the NSURLConnection loader is no longer supported.
  2018-12-13 16:25:47.491811+0800 Safari[49476:1264370] NSURLConnection finished with error - code -1100
  2018-12-13 16:25:47.799590+0800 Safari[49476:1264514] [CloudBookmarks] Error fetching remote migration state: Error Domain=com.apple.SafariBookmarksSync.CloudBookmarksErrorDomain Code=0 "(null)"
  2018-12-13 16:25:47.953259+0800 Safari[49476:1264277] [WebKit2Callbacks] Page (pid: 0) did become unresponsive
  2018-12-13 16:25:47.970927+0800 Safari[49476:1264512] NSURLConnection finished with error - code -1100
  2018-12-13 16:25:48.032647+0800 Safari[49476:1264425] [RemotePlistController] The downloaded plist could not be loaded: Error Domain=NSCocoaErrorDomain Code=260 "The file couldn’t be opened because it doesn’t exist."
  2018-12-13 16:25:48.125530+0800 Safari[49476:1264426] Calling IOPPFGetProperty simulator_utility_clamp!
  2018-12-13 16:25:48.840769+0800 Safari[49476:1264277] [WebKit2Callbacks] Page (pid: 49481) did become responsive
  </code></pre>
  
  <p>Now I'm running out of options. It lacks official documentation in Apple Developer site.</p>
  
  <p>Is there regular steps to troubleshoot this kind of issue? Is there any kind of system logs which can help me address the error? Any suggestion is appreciated.</p>