I am running Dart 2.0.0 with VSCode 1.26.1. I constantly see the following error written in Console under MacOS High Sierra 10.13.6:
nw_path_close_fd Failed to close guarded necp fd 6 [9: Bad file descriptor]
As soon as I close VSCode the dart process (and the error in the Console) goes away. Any ideas on why Dart is doing this? The offending library appears to be libsystem_network.dylib.
The dart process is any instance of a Dart VM running. VSCode will run a dart process for the realtime static analyzer, which feeds your warnings and errors panel. It may also be a Dart process that you launched from VSCode, the command-line, or another Dart process that the VSCode Dart plugin launches (other than the analyzer).
I can confirm that this issue does not occur when using IntelliJ IDEA and the Dart plugin. If you can isolate that it isn't the Dart code you are writing, I'd file a bug with the plugin repository: https://github.com/Dart-Code/Dart-Code/issues.