Failed to add json file when calling GetConfiguration()

[nicolegys]

Describe the bug
I tried to update the config file of RpcServer while neo-cli was running, but sometimes the neo-cli would throw exception and crash.

To Reproduce
Steps to reproduce the behavior:

1. start neo-cli.
2. change some settings in the config file of RpcServer, such as DisabledMethods, then save it.
3. most of the time, neo-cli will throw the exception and crash.

Platform:

• OS: [e.g. Windows 10 x64]
• Version
  neo-cli: 5a46401b3635b0f2f6a6b09141c20ea5ab361623
  neo: 6eba2ee
  neo-vm: f292fed3e9add32a2746e2c4cbb569d8dce6f25a
  neo-modules: bbcfa56171a931c1c6f2b50f9289350dd7c052c0

(Optional) Additional context
It seems that the json file wasn't added successfully.

When debugging, if I set a breakpoint, then continue, the file can be added successfully and not throw an excepiton.

The issue was found when testing neo-project/neo-modules#206

[Qiao-Jin]

I will have a look at this one.

[erikzhang]

I think the real reason is that WatcherChangeTypes.Changed will be triggered multiple times. Maybe we can just catch the exception and ignore it in the plugins.

[nicolegys]

I think the real reason is that WatcherChangeTypes.Changed will be triggered multiple times. Maybe we can just catch the exception and ignore it in the plugins.

You're right. When the config file is modified by editors like Notepad, the WatcherChangeTypes.Changed will be triggered once, but when modified by editors like VS code, the WatcherChangeTypes.Changed will be triggered twice, and GetConfiguration() will fail at the first time.

[erikzhang]

Then the fixes should be in the plugins.

[Qiao-Jin]

Then the fixes should be in the plugins.

Then we would need duplicate logic added everywhere func GetConfiguration called in plugins (config file changed, initialization)?

[shargon]

Agree with @Qiao-Jin , I think that it's better to fix it in the core and avoid duplicate code in modules.

[erikzhang]

Look at this:

neo/src/neo/Plugins/Plugin.cs

Lines 64 to 81 in 2fad68a

	private static void ConfigWatcher_Changed(object sender, FileSystemEventArgs e)
	{
	switch (GetExtension(e.Name))
	{
	case ".json":
	Plugins.FirstOrDefault(p => p.ConfigFile == e.FullPath)?.Configure();
	break;
	case ".dll":
	if (e.ChangeType != WatcherChangeTypes.Created) return;
	if (GetDirectoryName(e.FullPath) != PluginsDirectory) return;
	try
	{
	LoadPlugin(Assembly.Load(File.ReadAllBytes(e.FullPath)));
	}
	catch { }
	break;
	}
	}

The event is triggered when file is changed. Then it invokes the method Plugin.Configure(). Be careful, it is Configure(), not the GetConfiguration().

And the default Configure() is:

neo/src/neo/Plugins/Plugin.cs

Lines 60 to 62 in 2fad68a

	protected virtual void Configure()
	{
	}

As you can see, it does nothing. So you didn't fix anything if you catch the exception in GetConfiguration().

The most logical way is to call the GetConfiguration() in the plugin's overriding Configure(), which has already been done. And we just add some code around it to catch the exception.

[Qiao-Jin]

@nicolegys please have a test of the new PR:)