Remove session

[Rich-Harris]

Implements #5883. This removes event.session from load, the session store, and getSession. It's easy to use event.locals in handle along with +layout.server.js/+page.server.js to provide equivalent functionality.

Closes #4426.

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[rmunn]

I've closed two issues as moot now that session is gone:

• Add warning for use of session store outside of a component #5176
• Built-in method of refreshing session from server periodically #1726

A quick issue search on the word "session" turned up a lot of issues that mention that word, but only those two seemed to be specifically about the special session store that has just been removed. If this PR is reverted in the near future, we can reopen those issues.

[PH4NTOMiki]

What about SPA? This was a really bad move

[MathiasWP]

What about SPA? This was a really bad move

If you application is SPA only, then you should be able to achieve the same behaviour by creating your own store and calling it "session" 👍

[Rich-Harris]

If you have access to a server, then you can return the equivalent of session data from a +layout.server.js. If you don't, then you couldn't return session anyway.

[bjon]

@Rich-Harris How do I get the data from +layout.server.js, in +layout.js? await parent() is empty in +layout.js.

[dummdidumm]

https://kit.svelte.dev/docs/load#input-properties-data

[bjon]

@dummdidumm Thanks a lot! Didn't even know that data prop existed. 👍🏻