Add relative @import support

[k-g-a]

Fixes #47 and #48.

Adds support for local @import at-rules for pure css and less stylesheets.
It's done via passing proper from/filename to postcss/less renderers as discussed here.

I've also added couple of tests and postcss-import-sync2 dev dependency for those tests to work.

Unfortunatelly *.scss tests are failing for me with empty received snapshot (even at origin/develop without any modifications) and i've never worked with SCSS, so I did not dare to change anything related to scss. And I had to push with --no-verify to skip husky, but all other tests are passing.

As a side effect of those modifications local class names have changed: the common "file___" prefix is now substituted by real file name (i.e. "test-module__" or "import-module__") - this is reflected in snapshots. As those values are never ment to be used directly by anyone, this change does not seem relative or harmful in any way.

[k-g-a]

1. *.scss tests are failing because I could not update snapshot for those (prefix change)
2. other snapshots have different local class name suffix, but I'm not sure why...

It seems reasonable to enforce local class names without hashes for testing purposes via generateScopeName option of the postcss-icss-selectors plugin.

[mrmckeb]

Hi @k-g-a, I see that the tests are failing. If the classnames are changing, it could be related to your local env... I'll be able to dig into this properly on Monday I think.

[lianapache]

Hi @k-g-a, I updated snapshots locally and it seems to work fine. Probably, as @mrmckeb said, the problem is with you local env

[lianapache]

LGTM

[k-g-a]

@lianapache thanks! Unfirtunately I had no time to check it myself.
Class name prefixes and .scss snapshot updates are reasonable change (as explained above).
The only difference for which I can't figure out the reason are hashes (in css snapshot, for example). Could those be platform-dependant (i'm on windows)?

It seems to me that we need to add import.module.scss file same as for css/less version and add it to the testFileNames array in DtsSnapshotCreator.test.ts. I could not include those as the part of my initial PR as I could not make scss work.

[mrmckeb]

Hi @k-g-a, we've just released v2.0.0 which includes this PR and other changes.

Release notes and migration steps can be found here: https://github.com/mrmckeb/typescript-plugin-css-modules/releases/tag/v2.0.0

Please let me know if you have any other issues or feedback! And thanks for your patience.