fix: assert the option exists before sending it to the compiler

[cmizzi]

Using https://github.com/JeffreyWay/laravel-mix, options like context were sent to the compiler : it must not

[Conduitry]

There are other plugin options besides the ones given in that object - those are just default values I believe. And I don't think we want to be maintaining a list of valid options here as well as in the compiler. We should just be relying on the compiler to know what the valid options are, and projects like the above one need to not pass invalid options.

[Conduitry]

The unit tests here are failing because we need to be able to pass css and generate options to the compiler, and they're not listed in pluginOptions and so are ignored.

I don't believe svelte-loader should be doing anything differently here - laravel-mix would need to be updated.

[cmizzi]

laravel-mix, and possibly others, uses https://webpack.js.org/plugins/loader-options-plugin/. This plugin is sending more options to every registered plugins, and failed for svelte/compiler. It cannot be removed from laravel-mix and is not working with svelte-loader because of context option.

[0gust1]

The issue could be related to #89 (and #90). but lacks precisions about svelte compiler version and webpack version used.

[0gust1]

@cmizzi As #90 is now merged, maybe you would want to try again ? Make sure you use the latest svlete-loader version (I don't know laravel-mix beside the fact that's a webpack wrapper).

[cmizzi]

I already suggested a fix on laravel-mix to solve this problem : laravel-mix/laravel-mix#2089, so I could check with the previous state of laravel-mix if the bug is solved.