Allow use of function references as callbacks (#1067)

lib/nerdtree/key_map.vim

@@ -66,7 +66,7 @@ endfunction
 "FUNCTION: KeyMap.invoke() {{{1
 "Call the KeyMaps callback function
 function! s:KeyMap.invoke(...)
-    let Callback = function(self.callback)
+    let Callback = type(self.callback) == v:t_func ? self.callback : function(self.callback)
     if a:0
         call Callback(a:1)
     else

lib/nerdtree/menu_item.vim

@@ -79,7 +79,7 @@ endfunction
 "specified
 function! s:MenuItem.enabled()
     if self.isActiveCallback != -1
-        return {self.isActiveCallback}()
+        return type(self.isActiveCallback) == v:t_func ? self.isActiveCallback() : {self.isActiveCallback}()
     endif
     return 1
 endfunction
@@ -94,7 +94,11 @@ function! s:MenuItem.execute()
         call mc.showMenu()
     else
         if self.callback != -1
-            call {self.callback}()
+            if type(self.callback) == v:t_func
+                call self.callback()
+            else
+                call {self.callback}()
+            endif
         endif
     endif
 endfunction

lib/nerdtree/notifier.vim

@@ -14,8 +14,9 @@ endfunction
 function! s:Notifier.NotifyListeners(event, path, nerdtree, params)
     let event = g:NERDTreeEvent.New(a:nerdtree, a:path, a:event, a:params)
 
-    for listener in s:Notifier.GetListenersForEvent(a:event)
-        call {listener}(event)
+    for Listener in s:Notifier.GetListenersForEvent(a:event)
+    	let Callback = type(Listener) == v:t_func ? Listener : function(Listener)
+        call Callback(event)
     endfor
 endfunction
 

lib/nerdtree/path.vim

@@ -500,8 +500,9 @@ function! s:Path.ignore(nerdtree)
             endif
         endfor
 
-        for callback in g:NERDTree.PathFilters()
-            if {callback}({'path': self, 'nerdtree': a:nerdtree})
+        for Callback in g:NERDTree.PathFilters()
+            let Callback = type(Callback) == v:t_func ? Callback : function(Callback)
+            if Callback({'path': self, 'nerdtree': a:nerdtree})
                 return 1
             endif
         endfor