Svelte: Auto-subscribe to stores

[Rich-Harris]

Referencing a variable with a $ prefix should cause code similar to the following to be added:

import { onDestroy } from 'svelte';

let $foo;
onDestroy(foo.subscribe($$value => {
  $foo = $$value;
});

(See RFC 2 for an explanation.)

In dev mode, it should probably check that foo has a subscribe method first, and print a more helpful error.

Questions:

• If foo is not defined, what do we do? Assume $foo isn't the unwrapped value of a store?
• Do we do the same thing for reactive declarations?
• If $foo is already defined by the user, do we still add this code?

[TehShrike]

If foo is not defined, what do we do?

I vote for "throw a noisy error".

If $foo is already defined by the user, do we still add this code?

I vote for "throw a noisy error".

[Rich-Harris]

closed via #1880