fix: resolve effect_update_depth_exceeded with select bind:value in legacy mode #17645
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…egacy mode Move select value synchronization from a template_effect (which caused infinite loops when bound value derived from reactive statements) to the mutation point in AssignmentExpression. When a binding with indirect dependencies is mutated, invalidate_inner_signals is called inline instead of through an effect that re-reads the same signals. Closes sveltejs#13768
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Summary
Fixes #13768
<select bind:value={derived.prop}>in legacy (non-runes) components throwseffect_update_depth_exceededwhen the bound value comes from a$:reactive statement.Root cause:
setup_select_synchronizationcreated atemplate_effectthat calledinvalidate_inner_signals, which reads and writes the same signals on every change — creating an infinite update loop when those signals feed back into derived state.Fix: Remove the effect-based synchronization entirely. Instead, populate
legacy_indirect_bindingsduring the analyze phase for<select bind:value>elements, and callinvalidate_inner_signalsinline at the mutation point inAssignmentExpression— only when the binding is actually mutated, avoiding the read-write cycle.Based on the approach outlined in #16200.
Changes
scope.js: Addlegacy_indirect_bindingsfield toBindingclassRegularElement.js(analyze): For<select bind:value={foo}>, collect scope references as indirect bindings on the bound variableRegularElement.js(transform): Removesetup_select_synchronizationfunction and its call siteAssignmentExpression.js(transform): When mutating a binding with indirect bindings, appendinvalidate_inner_signalscall after the mutationTest plan
binding-select-reactive-derivedtest that reproduces the exact scenario from Broken page with Svelte 5: uncaughteffect_update_depth_exceeded#13768