fix: restore value after attribute removal during hydration

paoloricciuti commented 2 weeks ago

Svelte 5 rewrite

Fix #11457 ~the test is actually failing because i don't know how to write the test let the suite check the html only on the server and then assert that it changes on hydration. Is that even possible?~

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dummdidumm commented 2 weeks ago

There's ssrHtml to check SSRd HTML, and then there's variant (passed to the test function) which you can use to conditionally check something depending on which test variant (Dom, SSR, hydrate) runs

paoloricciuti commented 2 weeks ago

There's ssrHtml to check SSRd HTML, and then there's variant (passed to the test function) which you can use to conditionally check something depending on which test variant (Dom, SSR, hydrate) runs

Thanks...i actually figured that out just now...i've updated the test and changed one snapshot that was now failing. Maybe double check my test to see if this is actually the correct behaviour 😄

paoloricciuti commented 2 weeks ago

I don't think this is the right fix. The right fix is to fix the remove_input_attr_defaults function. Right now it just removes the attributes but it doesn't set the property, which means the value is just lost, leading to far more bugs than just this specific one. The fix is probably just this:
export function remove_input_attr_defaults(dom) {
  if (hydrating) {
      const value = dom.value;
      // @ts-expect-error
      const checked = dom.checked;
      set_attribute(dom, 'value', null);
      set_attribute(dom, 'checked', null);
      dom.value = value;
      // @ts-expect-error
      dom.checked = checked;
  }
}

Mmm...I was under the impression that after the removal hydration still did his job and the value was actually there. Infact in the test I also check that checked is true and it seems to pass. Am I wrong?

paoloricciuti commented 2 weeks ago

I don't think this is the right fix. The right fix is to fix the remove_input_attr_defaults function. Right now it just removes the attributes but it doesn't set the property, which means the value is just lost, leading to far more bugs than just this specific one. The fix is probably just this:
export function remove_input_attr_defaults(dom) {
  if (hydrating) {
      const value = dom.value;
      // @ts-expect-error
      const checked = dom.checked;
      set_attribute(dom, 'value', null);
      set_attribute(dom, 'checked', null);
      dom.value = value;
      // @ts-expect-error
      dom.checked = checked;
  }
}

Btw regardless I can change the fix to be the one you proposed if you think it's a better fix. I'll update the code later.

dummdidumm commented 2 weeks ago

It seems that it keeps the checked state, but the value state is definetly deleted. So yeah, we can micro-optimize that and don't do the checked set.

paoloricciuti commented 2 weeks ago

It seems that it keeps the checked state, but the value state is definetly deleted. So yeah, we can micro-optimize that and don't do the checked set.

So just to confirm, I'll fix with your code and remove the last line right?

paoloricciuti commented 2 weeks ago

@dummdidumm made a slight modification because reading dom.value was returning "on" when value was not set in checkboxes. This broke tests but also didn't seem like a good thing to have. It should be all green now

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