Polyfill imports can't be treeshaken

[NickColley]

When we import polyfills they're global.

Since a build system can't know where they're used, it can't make a decision to include it or not.

You can see an example of this here:

govuk-frontend/src/components/checkboxes/checkboxes.js

Line 1 in de2b8db

import '../../vendor/polyfills/Function/prototype/bind'

A potential solution would be to have a function that polyfills return that can be called.

import polyfillBind from '../../vendor/polyfills/Function/prototype/bind'
polyfillBind()

[NickColley]

Just realised this is only a problem if using the 'all' entry point. Which currently doesnt allow a destructured import.

So will close for now, may re-open if we decide to allow a destructured import.

[NickColley]

We now encourage a destructured import so this is an issue

[NickColley]

Actually, let's focus on ES6 modules tree shaking before this... Will add a comment to that instead.