!default for scss variables

[Ciantic]

Currently all variables in SCSS are defined using without !default.

In order for them to be overrideable all of them should be defined using !default, see SCSS references

This is related to #123

At least these files should be modified:

https://github.com/palantir/blueprint/blob/master/packages/core/src/common/_font-imports.scss#L7
https://github.com/palantir/blueprint/blob/master/packages/core/src/common/_variables.scss
https://github.com/palantir/blueprint/blob/master/packages/core/src/common/_color-aliases.scss

I'm not sure does this need a default in it:

https://github.com/palantir/blueprint/blob/master/packages/core/src/common/_colors.scss

[dmackerman]

There are also some cases where components aren't consuming variables, for example Button doesn't respect $pt-font-family. I'll see if I can put together a PR will all of these changes.

[adidahiya]

why does Button need to define font-family? Shouldn't it just inherit from base-typography which is applied to body?

[dmackerman]

@adidahiya I found it strange also, but the font didn't change unless I added the variable to @mixin pt-button-base()

[Reaverart]

So far I remember, webkit form elements not inherits font-family from body and uses default browser font. font-family: inherit; should fix.

[ugogo]

Shouldn't all vars has the !default param?

[dmackerman]

So now that the ~ import syntax is supported, this seems like something I could take a crack at doing now.

[giladgray]

certainly crack-worthy, i'd wager 🎩