Warn about invalid files not loaded on-load

Co-authored-by: rzvxa <[email protected]>

Author: Rafael Monico

lib/nerdtree/tree_dir_node.vim

@@ -421,13 +421,15 @@ function! s:TreeDirNode._initChildren(silent)
     endif
 
     let invalidFilesFound = 0
+    let invalidFiles = []
     for i in files
         try
             let path = g:NERDTreePath.New(i)
             call self.createChild(path, 0)
             call g:NERDTreePathNotifier.NotifyListeners('init', path, self.getNerdtree(), {})
         catch /^NERDTree.\(InvalidArguments\|InvalidFiletype\)Error/
             let invalidFilesFound += 1
+            let invalidFiles += [i]
         endtry
     endfor
 
@@ -437,7 +439,7 @@ function! s:TreeDirNode._initChildren(silent)
     call nerdtree#echo('')
 
     if invalidFilesFound
-        call nerdtree#echoWarning(invalidFilesFound . ' file(s) could not be loaded into the NERD tree')
+        call nerdtree#echoWarning(invalidFilesFound . ' Invalid file(s): ' . join(invalidFiles, ', '))
     endif
     return self.getChildCount()
 endfunction