Type Mismatch in @remix-run/node Library

[Garajluc]

Reproduction

After upgrading @remix-run/node from version ^2.7.0 to ^2.14.0, I encountered a type mismatch issue when using createCookieSessionStorage with a custom session data type. The type mismatch occurs because the createCookieSessionStorage function expects a generic type that extends SessionData, but it does not allow restricting the generic to specific keys.

Steps to Reproduce

1. Define a custom session data type with specific keys:

interface CustomSessionData {
  customProperty?: boolean;
}

2. Create a session storage using createCookieSessionStorage with the custom session data type:

import { createCookieSessionStorage } from "@remix-run/node";

export const sessionStorage = createCookieSessionStorage<CustomSessionData>({
  cookie: {...},
});

3. Use the session storage in an authenticator:

import { Authenticator } from "remix-auth";
import { sessionStorage } from "./session";

export const authenticator = new Authenticator<Auth>(sessionStorage, {
  sessionKey,
});

4. The sessionStorage usage in the step 3, yells the typescript error pasted in the "Actual Behavior" section

System Info

System:
    OS: macOS 14.1
    CPU: (11) arm64 Apple M3 Pro
    Memory: 125.41 MB / 18.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.11.0 - ~/.nvm/versions/node/v22.11.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v22.11.0/bin/yarn
    npm: 10.9.0 - ~/.nvm/versions/node/v22.11.0/bin/npm
  Browsers:
    Chrome: 130.0.6723.119
    Safari: 17.1
  npmPackages:
    @remix-run/dev: ^2.7.0 => 2.7.2 
    @remix-run/eslint-config: ^2.6.0 => 2.6.0 
    @remix-run/node: ^2.7.0 => 2.7.2 
    @remix-run/react: ^2.7.0 => 2.12.1 
    @remix-run/serve: ^2.7.0 => 2.7.2 
    @remix-run/testing: ^2.12.1 => 2.12.1 
    vite: ^5.4.8 => 5.4.8

Used Package Manager

npm

Expected Behavior

The custom session data type should be compatible with the SessionData interface, and there should be no type mismatch.

Actual Behavior

A type mismatch error occurs:

Argument of type 'SessionStorage<{ customProperty?: boolean | undefined; }, { customProperty?: boolean | undefined; }>' is not assignable to parameter of type 'SessionStorage<SessionData, SessionData>'.
  The types returned by 'getSession(...)' are incompatible between these types.
    Type 'Promise<Session<{ customProperty?: boolean | undefined; }, { customProperty?: boolean | undefined; }>>' is not assignable to type 'Promise<Session<SessionData, SessionData>>'.
      Type 'Session<{ customProperty?: boolean | undefined; }, { customProperty?: boolean | undefined; }>' is not assignable to type 'Session<SessionData, SessionData>'.
        Types of property 'get' are incompatible.
          Type '<Key extends "customProperty" >(name: Key) => (Key extends "customProperty" ? { customProperty?: boolean | undefined; }[Key] : undefined) | (Key extends "customProperty" ? { ...; ...' is not assignable to type '<Key extends string>(name: Key) => (Key extends string | number ? any : undefined) | (Key extends string | number ? any : undefined) | undefined'.
            Types of parameters 'name' and 'name' are incompatible.
              Type 'Key' is not assignable to type '"customProperty"'.
                Type 'string' is not assignable to type '"customProperty"'.