babel.config.js

module.exports = {
  presets: [
    [
      "@babel/preset-env",
      {
        useBuiltIns: "usage",
        corejs: {
          version: "3.6",
        },
        targets: {
          node: 10,
        },
        modules: "commonjs",
      },
    ],
  ],
  plugins: [
    [
      "@babel/plugin-transform-typescript",
      {
        isTSX: true,
        allExtensions: true,
        allowNamespaces: true,
        allowDeclareFields: true,
      },
    ],
    ["@babel/plugin-proposal-decorators", { legacy: true }],
    ["@babel/plugin-proposal-class-properties", { loose: false }],
    ["@babel/plugin-proposal-private-methods", { loose: false }],
    ...getRxjsTransforms(),
  ],
  ignore: ["**/*.d.ts"],
  only: [
    function(filepath) {
      const r = filepath.startsWith(__dirname) && /[\/\\]node_modules[\/\\]/.test(filepath) == false;
      return r;
    },
  ],
};

function getRxjsTransforms() {
  const rxjs = {
    Observable: "internal/Observable",
    ConnectableObservable: "internal/observable/ConnectableObservable",
    GroupedObservable: "internal/operators/groupBy",
    observable: "internal/symbol/observable",
    Subject: "internal/Subject",
    BehaviorSubject: "internal/BehaviorSubject",
    ReplaySubject: "internal/ReplaySubject",
    AsyncSubject: "internal/AsyncSubject",
    asapScheduler: "internal/scheduler/asap",
    asyncScheduler: "internal/scheduler/async",
    queueScheduler: "internal/scheduler/queue",
    animationFrameScheduler: "internal/scheduler/animationFrame",
    VirtualTimeScheduler: "internal/scheduler/VirtualTimeScheduler",
    Scheduler: "internal/Scheduler",
    Subscription: "internal/Subscription",
    Subscriber: "internal/Subscriber",
    Notification: "internal/Notification",
    pipe: "internal/util/pipe",
    noop: "internal/util/noop",
    identity: "internal/util/identity",
    isObservable: "internal/util/isObservable",
    ArgumentOutOfRangeError: "internal/util/ArgumentOutOfRangeError",
    EmptyError: "internal/util/EmptyError",
    ObjectUnsubscribedError: "internal/util/ObjectUnsubscribedError",
    UnsubscriptionError: "internal/util/UnsubscriptionError",
    TimeoutError: "internal/util/TimeoutError",
    bindCallback: "internal/observable/bindCallback",
    bindNodeCallback: "internal/observable/bindNodeCallback",
    combineLatest: "internal/observable/combineLatest",
    concat: "internal/observable/concat",
    defer: "internal/observable/defer",
    empty: "internal/observable/empty",
    forkJoin: "internal/observable/forkJoin",
    from: "internal/observable/from",
    fromEvent: "internal/observable/fromEvent",
    fromEventPattern: "internal/observable/fromEventPattern",
    generate: "internal/observable/generate",
    iif: "internal/observable/iif",
    interval: "internal/observable/interval",
    merge: "internal/observable/merge",
    never: "internal/observable/never",
    of: "internal/observable/of",
    onErrorResumeNext: "internal/observable/onErrorResumeNext",
    pairs: "internal/observable/pairs",
    race: "internal/observable/race",
    range: "internal/observable/range",
    throwError: "internal/observable/throwError",
    timer: "internal/observable/timer",
    using: "internal/observable/using",
    zip: "internal/observable/zip",
    EMPTY: "internal/observable/empty",
    NEVER: "internal/observable/never",
    config: "internal/config",
  };

  const rxjsAjax = {
    ajax: "internal/observable/dom/ajax",
    AjaxRequest: "internal/observable/dom/AjaxObservable",
    AjaxResponse: "internal/observable/dom/AjaxObservable",
    AjaxError: "internal/observable/dom/AjaxObservable",
    AjaxTimeoutError: "internal/observable/dom/AjaxObservable",
  };

  const transformImports = [
    [
      "transform-imports",
      {
        rxjs: {
          transform: (importName, matches) => `rxjs/${rxjs[importName]}`,
          preventFullImport: true,
          skipDefaultConversion: true,
        },
        "rxjs/ajax": {
          transform: (importName, matches) => `rxjs/${rxjsAjax[importName]}`,
          preventFullImport: true,
          skipDefaultConversion: true,
        },
        "rxjs/operators": {
          transform: "rxjs/internal/operators/${member}",
          preventFullImport: true,
          skipDefaultConversion: true,
        },
      },
    ],
  ];

  return transformImports;
}