fix: svelte:component evaluates props once

[ngtr6788]

Fixes #6634

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[dummdidumm]

Thank you! Could you add a changeset? Then we're good to merge.

[dorisip]

I think this change results in reactive props not being picked up by the component (See here).

Is this the new expected behavior?

[hackape]

@dorisip I looked into your repro and noticed a weird thing, switch_props(ctx) should have ctx as arg but is missing now. But I it isn't introduced by this PR, cus I also looked into v4.0.0 compiled code and the ctx is already missing there. Good catch through!

[jkbz64]

I'm having the same issue, this breaks my project, reactive props { ...props } do not change for components in svelte:component.

[hackape]

My investigation shows that, the bug actually originates from the implementation of switch_props(ctx) function, because ctx param is not used anywhere in the function body. Although compiled js code from Svelte compiler retain the ctx arg, I suspect it's optimized away by rollup bundler in REPL.

Current impl of switch_props fails to update switch_instance_props correctly, because it relies on outdated switch_instance_spread_levels, thus results in the bug.

const switch_instance_spread_levels = [/*props*/ ctx[1]];
var switch_value = /*view*/ ctx[0];

function switch_props(ctx) {
    let switch_instance_props = {};
    
    for (let i = 0; i < switch_instance_spread_levels.length; i += 1) {
	    switch_instance_props = assign(switch_instance_props, switch_instance_spread_levels[i]);
    }
    
    return {
	    props: switch_instance_props,
	    $$inline: true
    };
}

I tried to backtrace history of switch_props and couldn't find where it began to drop reference to ctx, it's been wrong for a really long time, 4+ years at least. This PR's is correct, it resolves a bug, it was that bug which shadows the real problem.