Feat/add config hook

[MoonBall]

Changes

do the stage 1 and stage 2 of #621

Testing

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/pikapkg/snowpack/3mra2hcje
✅ Preview: https://snowpack-git-fork-moonball-feat-add-config-hook.pikapkg.vercel.app

[FredKSchott]

Looks great! Left some comments

[FredKSchott]

I think there's an ordering problem here, where "name" may not yet be defined. Can execPluginFactory take an additional name argument, to make it explicit for the logger?

[MoonBall]

We maybe not know the name of plugin when we call the execPluginFactory function. So the name is assigned by name = plugin.name || pluginFactory.name.
The assign of name is executed before the executing of logWarn.
There is no case that name is undefined through running the yarn test.

[FredKSchott]

The ordering issue looks like it's at:

plugin = pluginFactory(configProxy, pluginOptions) as SnowpackPlugin;
  // This triggers the proxy, which triggers logWarn, which references `name` before it's set
name = plugin.name || pluginFactory.name;

[MoonBall]

Because the name of plugin is known after the pluginFactory returns, I delay the warn until the return of pluginFactory if plugin references snowpackConfig while generating plugin object.

[MoonBall]

The ordering issue looks like it's at:

plugin = pluginFactory(configProxy, pluginOptions) as SnowpackPlugin;
  // This triggers the proxy, which triggers logWarn, which references `name` before it's set
name = plugin.name || pluginFactory.name;

It's not happen. The assign of name is synchronously executed after the pluginFactory executes and returns.

Edit: if executing pluginFactory triggers the proxy, I set a flag needWarnAfterCreated = true and execute logWarn after assign of name.

[FredKSchott]

LGTM, I may move a few things around before release but overall this is great! Thanks for tackling!