Fix Babel options & Respect root's .babelrc

[lukeed]

If the user defines a .babelrc file in their root directory, we will read it & overwrite our settings with what they've specified. This is a hard/forced reset that they may choose to use.

Alternatively, a user may only want to modify the Babel configuration we've provided. Thanks to #56, they can do this now.

// preact.config.js

export default (config, env, helpers) => {
	let { rule } = helpers.getLoadersByName(config, 'babel-loader');
	rule.options.plugins.push('my-chosen-plugin');
};

---

Fixes #152 & others that were bound to open 😆

[lukeed]

Oh. This is because we're picking up our own .babelrc, which compiles to Node > 4 & overwrites all our shipped config (purposefully).

[rkostrzewski]

IMHO preact build - should use custom .babelrc. can be ignored for now

[rkostrzewski]

@lukeed actually it's because it's picking .babelrc in test dir which is using custom plugins array without jsx transform plugin

[lukeed]

Right, the repo's .babelrc is being parsed & overwriting our babel config.

It's doing what it's supposed to, we just have to ignore the root .babelrc & it'll be fine 😄

[developit]

We could move our babel config into the package.json

[thangngoc89]

My 2 cents:

Why don't we make a babel presets under preact-cli/babel for default babel config, so users can quickly pull them in. next.js does this

[lukeed]

@thangngoc89 I was going to suggest this too. Little more difficult since we have some conditional stuff, but should still be doable.

Tests failed because sourcemaps grew as a result of embedded options. @rkostrzewski is on it 🙌

[hassanbazzi]

Woooooooooo

[rkostrzewski]

@lukeed you're a star 🥇

[lukeed]

@rkostrzewski no, you 🌟 Thanks for editing the how-to above 🙌

[ekanna]

// preact.config.js

export default (config, env, helpers) => {
	let { rule } = helpers.getLoadersByName(config, 'babel-loader');
	rule.options.plugins.push('my-chosen-plugin');
};

helpers.getLoadersByName(config, 'babel-loader') returns array.
so change code to below in docs:

// preact.config.js

export default (config, env, helpers) => {
	let { rule } = helpers.getLoadersByName(config, 'babel-loader')[0];
	rule.options.plugins.push('my-chosen-plugin');
};

Also change in examples at
https://github.com/developit/preact-cli/wiki/Config-Recipes#customising-babel-options-using-loader-helpers