Svelte 5: select bindings broken when options rendered via #each loop

[theodorejb]

Describe the bug

When a select element value binding doesn't match an option, no option should be selected. This works correctly in Svelte 4 and is tested in tests/runtime-legacy/samples/binding-select-unmatched. However, it is broken in Svelte 5 when the option elements are rendered from an array via an #each loop (rather than hardcoded like they are in the test). The first option incorrectly appears selected, even though its value doesn't match the select element value binding.

Secondly, when a select element value binding is initially undefined, then the first non-disabled or selected option value should be selected (and the bound variable set to its value). This also works in Svelte 4, and is tested via tests/runtime-legacy/samples/binding-select-initial-value-undefined and tests/runtime-legacy/samples/binding-select-initial-value-undefined-2. However, this is likewise broken in Svelte 5 when the options are rendered via an #each loop. The expected option appears selected, but the variable bound to the select value fails to be initialized with the selected option value.

Reproduction

binding-select-unmatched broken when options rendered in each loop.

binding-select-initial-value-undefined broken when options rendered in each loop.

Logs

No response

System Info

Firefox, Chromium, Edge

Severity

blocking an upgrade