Custom build with browserslist

[fenderil]

Hi there.

How about modify core-js-builder with browserslist and caniuse-db (or some other feature db)? It's would be useful to exclude some imports, that don't need to be polyfiiled.

[zloirock]

• I don't think that this issue in the scope of core-js-builder. My position - it's a legacy feature for cases when you should exclude something certain from core-js. Something like Breaks Number matching in Meteor #38. In other cases, it would be better just import required core-js features to your code and use something like webpack.
• caniuse-db is a bad data source for this data.
• You could try @babel/preset-env with useBuiltIns option. Seems it's what you need. However, @babel/preset-env use compat-table which also is not a good data source for that.
• Need to think about an alternative core-js-oriented data source for that and, maybe, about a better solution for providing polyfills, required only for target engines.

[fenderil]

• Fine. On the other hand I had an idea about json generation, that includes only required and unsupported features.
• Yeah, caniuse-db is not so good.
• I had seen this. It's looks like what I need, but not. :) I need to generate features pack for single injection on document start, for reuses between modules and pages with window.history and different bundles. But why compat-table is not a good data source? Just interesting.
• I think there could be detached package, that definitely know all relations between features and engines, and this package generate json meta with usage of browserslist and unused_feature_list.

I can pick it for implementation.

[zloirock]

@fenderil sorry, I missed your answer.

#466 fixes this issue. Also, in this PR you can find argumentation.

[fenderil]

That is what i expected.