babel-polyfill.js

// @flow

import { getImportSource, getRequireSource, isPolyfillSource } from "./utils";

import type { NodePath } from "@babel/traverse";

const BABEL_POLYFILL_DEPRECATION = `
  \`@babel/polyfill\` is deprecated. Please, use required parts of \`core-js\`
  and \`regenerator-runtime/runtime\` separately`;

const NO_DIRECT_POLYFILL_IMPORT = `
  When setting \`useBuiltIns: 'usage'\`, polyfills are automatically imported when needed.
  Please remove the direct import of \`SPECIFIER\` or use \`useBuiltIns: 'entry'\` instead.`;

export default function ({ template }, { regenerator, deprecated, usage }) {
  return {
    name: "preset-env/replace-babel-polyfill",
    visitor: {
      ImportDeclaration(path: NodePath) {
        const src = getImportSource(path);
        if (usage && isPolyfillSource(src)) {
          console.warn(NO_DIRECT_POLYFILL_IMPORT.replace("SPECIFIER", src));
          if (!deprecated) path.remove();
        } else if (src === "@babel/polyfill") {
          if (deprecated) {
            console.warn(BABEL_POLYFILL_DEPRECATION);
          } else if (regenerator) {
            path.replaceWithMultiple(template.ast`
              import "core-js";
              import "regenerator-runtime/runtime.js";
            `);
          } else {
            path.replaceWith(template.ast`
              import "core-js";
            `);
          }
        }
      },
      Program(path: NodePath) {
        path.get("body").forEach(bodyPath => {
          const src = getRequireSource(bodyPath);
          if (usage && isPolyfillSource(src)) {
            console.warn(NO_DIRECT_POLYFILL_IMPORT.replace("SPECIFIER", src));
            if (!deprecated) bodyPath.remove();
          } else if (src === "@babel/polyfill") {
            if (deprecated) {
              console.warn(BABEL_POLYFILL_DEPRECATION);
            } else if (regenerator) {
              bodyPath.replaceWithMultiple(template.ast`
                require("core-js");
                require("regenerator-runtime/runtime.js");
              `);
            } else {
              bodyPath.replaceWith(template.ast`
                require("core-js");
              `);
            }
          }
        });
      },
    },
  };
}