babel 7.x - Can't resolve 'core-js/modules/es.array.concat' - babeljs

Question

I upgraded babel 6.x → 7.x but having issues running Webpack.
It is complaining about missing core-js/modules/*.
My babel.config.js is in the root directory. I converted the previously existing .babelrc to js (.babelrc also produced the same errors). I am guessing it is some collision with all the core, corejs2, runtime stuff.
There are two apps in my src, mine and Styleguidist (in ./node_modules). My app transpiles and works with these same package.json/babel.config, but Styleguidist does not.
The error when running Styleguidist with webpack:
Module not found: Error: Can't resolve 'core-js/modules/es.array.concat' in '/project/src/node_modules/react-styleguidist/lib/client/rsg-components/Slot'
/node_modules/react-styleguidist/lib/client/rsg-components/Slot.js:
import "core-js/modules/es.array.concat";
import "core-js/modules/es.array.filter";
...
package.json
"dependencies": {
"#babel/polyfill": "^7.0.0",
"#babel/runtime-corejs2": "^7.4.3",
}
"devDependencies": {
"#babel/core": "^7.4.3",
"#babel/plugin-proposal-class-properties": "^7.0.0",
"#babel/plugin-proposal-decorators": "^7.0.0",
"#babel/plugin-proposal-export-namespace-from": "^7.0.0",
"#babel/plugin-proposal-function-sent": "^7.0.0",
"#babel/plugin-proposal-json-strings": "^7.0.0",
"#babel/plugin-proposal-numeric-separator": "^7.0.0",
"#babel/plugin-proposal-object-rest-spread": "^7.4.3",
"#babel/plugin-proposal-throw-expressions": "^7.0.0",
"#babel/plugin-syntax-dynamic-import": "^7.0.0",
"#babel/plugin-syntax-import-meta": "^7.0.0",
"#babel/plugin-syntax-jsx": "^7.0.0",
"#babel/plugin-transform-modules-commonjs": "^7.4.3",
"#babel/plugin-transform-react-jsx": "^7.3.0",
"#babel/plugin-transform-runtime": "^7.4.3",
"#babel/preset-env": "^7.4.3",
"#babel/register": "^7.0.0",
"babel-core": "^7.0.0-bridge.0",
"babel-eslint": "^10.0.1",
"babel-helper-vue-jsx-merge-props": "^2.0.3",
"babel-jest": "^24.7.1",
"babel-loader": "^8.0.0",
"babel-plugin-dynamic-import-node": "^2.2.0",
"babel-plugin-transform-vue-jsx": "^4.0.1",
}
babel.config.js
module.exports = {
presets: ['#babel/preset-env'],
plugins: [
'#babel/plugin-transform-runtime',
'#babel/plugin-transform-react-jsx',
'transform-vue-jsx',
"#babel/plugin-proposal-object-rest-spread",
"#babel/plugin-syntax-dynamic-import",
"#babel/plugin-syntax-import-meta",
"#babel/plugin-proposal-class-properties",
"#babel/plugin-proposal-json-strings",
[
"#babel/plugin-proposal-decorators",
{
"legacy": true
}
],
"#babel/plugin-proposal-function-sent",
"#babel/plugin-proposal-export-namespace-from",
"#babel/plugin-proposal-numeric-separator",
"#babel/plugin-proposal-throw-expressions"],
comments: false
}

Answer 1

Quoting from Babel 7.4.0 release :
#babel/polyfill isn't a plugin or preset, but a runtime package: if we added an option to switch between core-js#2 and core-js#3, both the package versions would need to be included in your bundle. For this reason, we decided to deprecate it: you now should load core-js for polyfills, and regenerator-runtime/runtime if you are transforming generators:
As you are using 7.4.3 version of babel, #babel/polyfill might not work as expected. Instead please add core-js and regenerator-runtime manually. Quoting from core-js3 release announcement:
Instead of
import "#babel/polyfill";
you should use those 2 lines:
import "core-js/stable";
import "regenerator-runtime/runtime";
Don't forget install those dependencies directly!
npm i --save core-js regenerator-runtime

Answer 2

I had the same issue and as often happens I forgot to have another package installed as:
"#babel/runtime-corejs3": "^7.5.5",
Don't forgot to install it at same level where you have the issue(either dev, local or production) level:
npm i -D(or --save-dev) #babel/runtime-corejs3
So in general this kind of errors happens when there are dependencies update change significantly in the version and aren't backward compatible with previous versions(API changes). Indeed corejs3 isn't at all compatible with corejs2 or older.

Answer 3

I found possible answer.
To resolve this error, you can downgrade the core-js version to 2.5.7. This version produces correct catalogs structure, with separate ES6 and ES7 folders.
To downgrade the version, simply run:
npm i -S core-js#2.5.7