feat: add support session typing

[ascorbic]

Changes

Adds support for typing experimental session data. This works similarly to typing of Astro.locals, using src/env.d.ts to define ambient types that extend App.SessionData. For example:

declare namespace App {
  interface SessionData {
    user: {
      id: string;
      email: string;
    };
    lastLogin: Date;
  }
}

Any keys not defined in this interface will be treated as any.

Then when you access Astro.session in your components, any defined keys will be typed correctly:

---
const user = await Astro.session.get('user');
//    ^? const: user: { id: string; email: string; } | undefined

const something = await Astro.session.get('something');
//    ^? const: something: any

Astro.session.set('user', 1);
//    ^? Argument of type 'number' is not assignable to parameter of type '{ id: string; email: string; }'.
---

Testing

Tested manually

Docs

Docs PR: withastro/docs#11068
RFC update to follow

[changeset-bot]

🦋 Changeset detected

Latest commit: 39a3048

The changes in this PR will be included in the next version bump.

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[codspeed-hq]

CodSpeed Performance Report

Merging #13320 will not alter performance

_{Comparing session-types (39a3048) with main (5f72a58)}

Summary

✅ 6 untouched benchmarks

[ascorbic]

This is to be merged after the 5.4 release

[ematipico]

Blocking to avoid merge

[florian-lefebvre]

Could it be possible to add types tests under test/types?

[ascorbic]

@florian-lefebvre done

[florian-lefebvre]

Looks like you have unused imports in the test, but apart from that looks good!

5.4 is out