Variable map is always overwritten by local vars

[aaronj1335]

@necolas the other day in https://gitter.im/webpack/webpack you suggested using a global variable map as a workaround for full-blown variable parsing on individual CSS modules (wish i could link to the convo, but it was around Sept 8th at ~11 AM PST).

it was pretty straitforward to implement, as you suggested, but the global variables are overwritten by the local defaults, which is a problem when working with suitcss-style packages, because they usually define local defaults.

does any of that make sense?

one proposal would be to provide another config flag to rework-vars that specifies whether the map is overwritten or not. another would be to accept a function that resolves the conflict given some context info.

what do you think? i'd be happy to submit a PR.

[aaronj1335]

after thinking about this more, another stop-gap is to make a rework plugin that strips the local variable definitions that are already in the map. this avoids the issue without complicating the rework-vars api, so i'm not really sure if any action is needed here.

[necolas]

perhaps the JS variables should not be be overridden? or they get added after everything is extracted from the css.

[aaronj1335]

yea i think you'll get the same behavior either way right? adding the JS-defined vars after extracting sounds like a clean way to do it. also seems like that should be the default, tho i've got limited experience with this. we could also add a config for applying before or after.