SvelteReference

Runtime warnings

Client warnings

binding_property_non_reactive

`%binding%` is binding to a non-reactive property

`%binding%` (%location%) is binding to a non-reactive property

console_log_state

Your `console.%method%` contained `$state` proxies. Consider using `$inspect(...)` or `$state.snapshot(...)` instead

When logging a proxy, browser devtools will log the proxy itself rather than the value it represents. In the case of Svelte, the ‘target’ of a $state proxy might not resemble its current value, which can be confusing.

The easiest way to log a value as it changes over time is to use the $inspect rune. Alternatively, to log things on a one-off basis (for example, inside an event handler) you can use $state.snapshot to take a snapshot of the current value.

event_handler_invalid

%handler% should be a function. Did you mean to %suggestion%?

hydration_attribute_changed

The `%attribute%` attribute on `%html%` changed its value between server and client renders. The client value, `%value%`, will be ignored in favour of the server value

hydration_html_changed

The value of an `{@html ...}` block changed between server and client renders. The client value will be ignored in favour of the server value

The value of an `{@html ...}` block %location% changed between server and client renders. The client value will be ignored in favour of the server value

hydration_mismatch

Hydration failed because the initial UI does not match what was rendered on the server

Hydration failed because the initial UI does not match what was rendered on the server. The error occurred near %location%

invalid_raw_snippet_render

The `render` function passed to `createRawSnippet` should return HTML for a single element

legacy_recursive_reactive_block

Detected a migrated `$:` reactive block in `%filename%` that both accesses and updates the same reactive value. This may cause recursive updates when converted to an `$effect`.

lifecycle_double_unmount

Tried to unmount a component that was not mounted

ownership_invalid_binding

%parent% passed a value to %child% with `bind:`, but the value is owned by %owner%. Consider creating a binding between %owner% and %parent%

ownership_invalid_mutation

Mutating a value outside the component that created it is strongly discouraged. Consider passing values to child components with `bind:`, or use a callback instead

%component% mutated a value owned by %owner%. This is strongly discouraged. Consider passing values to child components with `bind:`, or use a callback instead

state_proxy_equality_mismatch

Reactive `$state(...)` proxies and the values they proxy have different identities. Because of this, comparisons with `%operator%` will produce unexpected results

$state(...) creates a proxy of the value it is passed. The proxy and the value have different identities, meaning equality checks will always return false:

<script>
	let value = { foo: 'bar' };
	let proxy = $state(value);

	value === proxy; // always false
</script>

To resolve this, ensure you’re comparing values where both values were created with $state(...), or neither were. Note that $state.raw(...) will not create a state proxy.

Shared warnings

dynamic_void_element_content

`<svelte:element this="%tag%">` is a void element — it cannot have content

state_snapshot_uncloneable

Value cannot be cloned with `$state.snapshot` — the original value was returned

The following properties cannot be cloned with `$state.snapshot` — the return value contains the originals:

%properties%

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