Plugins Implementation

[tconley1428]

What was changed

Add plugin types for Connection, NativeConnection, Worker, Client, and Bundler, as well as a SimplePlugin class for easy construction of new plugins.

Why?

Plugins make it easier to share common configurations and apply them consistently.

Checklist

1. Closes [Feature Request] Plugin support #1764

2. How was this tested:

3. Any docs updates needed?

[chris-olszewski]

Overall, this design makes sense to me.

[chris-olszewski]

Would we ever expect/support a plugin altering the plugin list?

I'm not sure I can think of a reason for doing this, but the current implementation would allow altering the list, but the iteration wouldn't change. e.g. a removed plugin can still alter the options/added plugin will not get a chance to alter the options

[tconley1428]

We don't intend to support that. If you have an idea of how to enforce that, we could.

[chris-olszewski]

You could leverage Omit to make it clear that plugins won't be respected e.g. configureClient?(options: ClientOptions): Omit<ClientOptions, 'plugins'>

Running the configurations becomes a little more awkward as you have to destructure options each iteration e.g.

    // Add client plugins from the connection
    options.plugins = (options.plugins ?? []).concat(options.connection?.plugins ?? []);
    let { plugins, ...optionsWithoutPlugins } = options;

    // Process plugins first to allow them to modify connect configuration
    for (const plugin of options.plugins) {
      if (plugin.configureClient !== undefined) {
        optionsWithoutPlugins = plugin.configureClient({...optionsWithoutPlugins, plugins });
      }
    }
    options = { ...optionsWithoutPlugins, plugins };

    super(options);

It doesn't warn/error if the user tries to alter the plugin list, but any changes they make won't be respected.

[tconley1428]

Omit is a good idea. It seems like I can just change the type in the plugin to Omit<ClientOptions, "plugins"> without any other change. They can return something with changed plugins, but expresses the intent