GH-360 Show reason when the IPC got invalid

SwiftNeoVim/NeoVimAgent.m

@@ -395,7 +395,9 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
 
   if (responseCode != kCFMessagePortSuccess) {
     log_cfmachport_error(responseCode, msgid, data);
-    [_bridge ipcBecameInvalid];
+    [_bridge ipcBecameInvalid:
+        [NSString stringWithFormat:@"Reason: sendMsg failed for %d with %d", msgid, responseCode]
+    ];
     return nil;
   }
 

SwiftNeoVim/NeoVimUiBridgeProtocol.h

@@ -123,7 +123,7 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)stop;
 
-- (void)ipcBecameInvalid;
+- (void)ipcBecameInvalid:(NSString *)reason;
 
 @end
 

SwiftNeoVim/NeoVimView.swift

@@ -89,7 +89,7 @@ public class NeoVimView: NSView, NeoVimUiBridgeProtocol, NSUserInterfaceValidati
   public var cwd: URL {
     get {
       guard let output = self.agent.vimCommandOutput("silent pwd") else {
-        self.ipcBecameInvalid()
+        self.ipcBecameInvalid("Reason: 'silent pwd' failed")
         return URL(fileURLWithPath: NSHomeDirectory())
       }
 
@@ -730,7 +730,7 @@ extension NeoVimView {
     }
 
     guard let curPasteMode = self.agent.boolOption("paste") else {
-      self.ipcBecameInvalid()
+      self.ipcBecameInvalid("Reason: 'set paste' failed")
       return
     }
 
@@ -1438,10 +1438,10 @@ extension NeoVimView {
     }
   }
 
-  public func ipcBecameInvalid() {
+  public func ipcBecameInvalid(_ reason: String) {
     NSLog("ERROR \(#function): force-quitting")
     DispatchUtils.gui {
-      self.delegate?.ipcBecameInvalid()
+      self.delegate?.ipcBecameInvalid(reason: reason)
       self.agent.quit()
     }
   }

SwiftNeoVim/NeoVimViewDelegate.swift

@@ -14,5 +14,5 @@ public protocol NeoVimViewDelegate: class {
   func cwdChanged()
   func bufferListChanged()
 
-  func ipcBecameInvalid()
+  func ipcBecameInvalid(reason: String)
 }

VimR/MainWindowComponent.swift

@@ -483,11 +483,12 @@ extension MainWindowComponent {
     self.publish(event: MainWindowAction.changeBufferList(mainWindow: self, buffers: buffers))
   }
 
-  func ipcBecameInvalid() {
+  func ipcBecameInvalid(reason: String) {
     let alert = NSAlert()
     alert.addButton(withTitle: "Close")
     alert.messageText = "Sorry, an error occurred."
-    alert.informativeText = "VimR encountered an error from which it cannot recover. This window will now close."
+    alert.informativeText = "VimR encountered an error from which it cannot recover. This window will now close.\n"
+      + reason
     alert.alertStyle = .critical
     alert.beginSheetModal(for: self.window) { [weak self] response in
       self?.windowController.close()