tsconfig.json

{
  "compilerOptions": {
    "target": "ES2021",
    "module": "ES2020",
    "moduleResolution": "node",

    // Trying to check Ember apps and addons with `allowJs: true` is a recipe
    // for many unresolveable type errors, because with *considerable* extra
    // configuration it ends up including many files which are *not* valid and
    // cannot be: they *appear* to be resolve-able to TS, but are in fact not in
    // valid Node-resolveable locations and may not have TS-ready types. This
    // will likely improve over time
    "allowJs": false,

    // --- TS for SemVer Types compatibility
    // Strictness settings -- you should *not* change these: Ember code is not
    // guaranteed to type check with these set to looser values.
    "strict": true,
    "noUncheckedIndexedAccess": true,

    // Interop: these are viral and will require anyone downstream of your
    // package to *also* set them to true. If you *must* enable them to consume
    // an upstream package, you should document that for downstream consumers to
    // be aware of.
    //
    // These *are* safe for apps to enable, since they do not *have* downstream
    // consumers; but leaving them off is still preferred when possible, since
    // it makes it easier to switch between apps and addons and have the same
    // rules for what can be imported and how.
    "allowSyntheticDefaultImports": false,
    "esModuleInterop": false,

    // --- Lint-style rules

    // TypeScript also supplies some lint-style checks; nearly all of them are
    // better handled by ESLint with the `@typescript-eslint`. This one is more
    // like a safety check, though, so we leave it on.
    "noPropertyAccessFromIndexSignature": true,

    // --- Compilation/integration settings
    // Setting `noEmitOnError` here allows ember-cli-typescript to catch errors
    // and inject them into Ember CLI's build error reporting, which provides
    // nice feedback for when
    "noEmitOnError": true,

    // We use Babel for emitting runtime code, because it's very important that
    // we always and only use the same transpiler for non-stable features, in
    // particular decorators. If you were to change this to `true`, it could
    // lead to accidentally generating code with `tsc` instead of Babel, and
    // could thereby result in broken code at runtime.
    "noEmit": true,

    // Ember makes heavy use of decorators; TS does not support them at all
    // without this flag.
    "experimentalDecorators": true,

    // Support generation of source maps. Note: you must *also* enable source
    // maps in your `ember-cli-babel` config and/or `babel.config.js`.
    "declaration": true,
    "declarationMap": true,
    "inlineSourceMap": true,
    "inlineSources": true,

    // The combination of `baseUrl` with `paths` allows Ember's classic package
    // layout, which is not resolveable with the Node resolution algorithm, to
    // work with TypeScript.
    "baseUrl": ".",

    "paths": {
      "dummy/tests/*": ["tests/*"],
      "dummy/*": ["tests/dummy/app/*", "app/*"],
      "ember-cognito-identity": ["addon"],
      "ember-cognito-identity/*": ["addon/*"],
      "ember-cognito-identity/test-support": ["addon-test-support"],
      "ember-cognito-identity/test-support/*": ["addon-test-support/*"],
      "*": ["types/*"]
    }
  }
}