RJS-2732: Support updating the App's base URL via experimental export

[elle-j]

What, How & Why?

Experimental exports/imports

• An experimental directory has been added (packages/realm/src/experimental), intended for exporting various experimental features.

Base URL

• Importing "realm/experimental/base-url" will extend the App with the instance members App.baseUrl and App.updateBaseUrl(), allowing the user to retrieve and update the base URL.

TSConfig / Choosing module resolution

• Importing the experimental package will only work with certain resolution algorithms. Example tsconfig.json:

{
  "compilerOptions": {
    "target": "es2022",
    "module": "node16",
    "moduleResolution": "node16",
    // ...
  }
}

Example Usage

import { App } from "realm";
import "realm/experimental/base-url";

async function exampleFunction() {
  const app = new App("my-atlas-app-id");

  // Get the currently used base URL.
  const currentBaseUrl = app.baseUrl;

  // Update the base URL.
  await app.updateBaseUrl("https://my-new-url.com");

  // Reset it to the default one.
  await app.updateBaseUrl(null);
}

This closes #6486

☑️ ToDos

• 📝 Changelog entry
• 🚦 Tests (but need to add follow-ups to skipped unimplemented tests)

[nirinchev]

Nice! Might be worth adding a smoke test that updating the base url to a valid url also works. We could try and use realm.mongodb.com since that domain should still work.

[elle-j]

Just reviving the old draft implementation then I'll be modifying the test and adding some more 🙂

[elle-j]

Will add this using a fetch mock.

[kraenhansen]

Did you check this works with npm test --workspace @realm/integration-tests (where we use raw Mocha and tsx to transpile TypeScript)?

[elle-j]

Works ✅

[kraenhansen]

Well - even if this wasn't a problem, we would probably need this file anyway, to workaround the fact that unstable_enablePackageExports is disabled by default 🤔

[kraenhansen]

Also ... I know for a fact that the Metro team would be very grateful if someone would set up some tests of the metro resolver (most likely copying in tests from other packages / tools). This would make a good test case if the pattern isn't already covered by one of those other tests.

[elle-j]

I've updated the comment to incorporate being disabled by default. Feel free to suggest any additional changes you think would be relevant for this file 👍

I'd be glad to look over some of the Metro tests and see what could be added. At first glance, it does seem like their tests are covering subpath exports.

[kraenhansen]

I wonder why this was not already on main 🤔

[elle-j]

Probably just didn't get committed 🤷‍♀️

[kneth]

Nice work!

[elle-j]

@kneth, for the final review there are only minor changes to look at:

• CHANGELOG.md
• packages/realm/src/experimental/base-url.ts: Per another discussion, the API updateBaseUrl() now accepts null as a way to reset the base URL to the default one (in addition to empty string).

Still missing:

• Haven't got the mock fetch to work yet, so I'll add a ticket to implement the skiped tests.