Using external helpers plugin rather than preset

[madeleineostoja]

Because of situations like #12 and #3 I'm trying to use the es2015 preset with the external-helpers-2 plugin in my .babelrc, as suggested in the README. But rollup-plugin-babel still complains about using es2015 rather than es2015-rollup. Is it possible to use es2015 + external-helpers?

[Rich-Harris]

es2015 includes the CommonJS transformer, which makes Rollup's job impossible (no ES6 modules). Because of that, the first .babelrc file Babel finds (it stops looking once it's found the nearest one) can't have the es2015 preset.

The best bet is probably to have a .babelrc in the root of your project with es2015, and another src/.babelrc (or whatever) that uses es2015-rollup. Your test runner/Gulp/whatever won't see src/.babelrc, and Rollup won't see the root .babelrc. Let me know if that works, I haven't tried it yet!

[madeleineostoja]

No luck, getting

Error: External helpers are not enabled. Please add the "external-helpers-2" plugin or use the "es2015-rollup" preset. See https://github.com/rollup/rollup-plugin-babel#TK for more information

with es2015-rollup specified in a local .babelrc (in src dir). And if I specify the preset in the plugin directly as well as have a local .babelrc it complains about the root .babelrc

[Rich-Harris]

Ah, I figured out what's going on here – it runs the 'preflight checks' (ensuring module transformation is disabled and external helpers are enabled) in the cwd, which means it picks up the root .babelrc. Changed so that it runs preflight checks for each file before transpilation. Slight overhead but only way to ensure correct configuration throughout.

[Rich-Harris]

Meant to add – released 2.2.0 with a fix

[madeleineostoja]

Awesome, thanks! Might be worth explicitly documenting this pattern in the readme? I feel it's a reasonably common use-case, needing to use es2015 for some things in a codebase and rollup for others.