IE11 is not dead yet, and our library is supposed to run there and make russian grandmas happy. As you can guess, we rely on babel's preset-env a lot. We also don't want our code to be 55% babel helpers, so we use babel's transform-runtime — it should make babel import someHelper from '@babel/runtime/some-helper' instead of inlining it into every file. After making some build chain updates I went to see if the transpiled version was OK. And guess what I noticed? Some babel helpers were still there, inlined:

import _defineProperty from "@babel/runtime/helpers/defineProperty";
// go away transform do you have any idea who I am?
function ownKeys(object, enumerableOnly) { /* blah-blah-blah */ }
function _objectSpread(target) { /* more blah-blah-blah */ }

var copy = function copy(obj) {
  return _objectSpread({}, options);
};

WTF? I want to import _objectSpread, you lazy code! What's wrong with you? A leak from an external library? An unexpected interaction with preset-react or preset-typescript? Corrupt installation? Babel bugs? No, no, no, no.

The answer was simple — transform-runtime wants me to tell it what @babel/runtime version I have via the version option. For some reason, transform-runtime assumes you have @babel/runtime version 7.0.0, and if a helper was not in runtime@7.0.0, it won't bother importing it. Babel is at 7.15.x now, and a lot has changed. Anyways, if you pass the real runtime version you installed:

exports = {
  "plugins": [
    ["@babel/plugin-transform-runtime", {
      // this is the magic line
      "version": "7.15.0"
    }]
  ]
}

transform-runtime will finally do its job as it should:

import _objectSpread from "@babel/runtime/helpers/objectSpread2";
var copy = _objectSpread({}, props);

If you'd rather do it once, use babel.config.js and read the runtime version from package.json — both your dependency range and the version in node_modules work fine, though I feel the latter is cleaner:

// in babel.config.js
const requiredVersion = require('./package.json').dependencies['@babel/runtime'];
const installedVersion = require('@babel/runtime/package.json').version;

If you want your @babel/plugin-transform-runtime not to get lazy and really deduplicate all the helpers, set transform-runtime's version option to the current @babel/runtime version. Also keep your babel stack updated, and try to match @babel/* versions. You're welcome.