babel.config.cjs

module.exports = {
    sourceMaps: true,
    presets: [
        [
            "@babel/preset-env",
            {
                targets: {
                    esmodules: true,
                },
                // We want to output ES modules for the final build (mostly to ensure that
                // async imports work correctly). However, jest doesn't support ES modules very
                // well yet (see https://github.com/jestjs/jest/issues/9430), so we use commonjs
                // when testing.
                modules: process.env.NODE_ENV === "test" ? "commonjs" : false,
            },
        ],
        [
            "@babel/preset-typescript",
            {
                // When using the transpiled javascript in `lib`, Node.js requires `.js` extensions on any `import`
                // specifiers. However, Jest uses the TS source (via babel) and fails to resolve the `.js` names.
                // To resolve this,we use the `.ts` names in the source, and rewrite the `import` specifiers to use
                // `.js` during transpilation, *except* when we are targetting Jest.
                rewriteImportExtensions: process.env.NODE_ENV !== "test",
            },
        ],
    ],
    plugins: [
        "@babel/plugin-transform-numeric-separator",
        "@babel/plugin-transform-class-properties",
        "@babel/plugin-transform-object-rest-spread",
        "@babel/plugin-syntax-dynamic-import",
        "@babel/plugin-transform-runtime",
    ],
};