remotion-dev/remotion · error

Cannot reorder effect: source effect is not-call-expression

Error message

Cannot reorder effect: source effect is not-call-expression

What it means

reorderEffect() only supports moving entries of the effects array that are plain call expressions like <FadeIn/> style effects={[(interpolate(...), Spring())]}. If the element at fromIndex is a spread element, hole, or any other non-call node, it throws this error. The reorder operation cannot represent such entries safely when moving them.

Solutions

1. Choose a fromIndex that points at an actual effect call (e.g. the Spring() or interpolate() entry).
2. Rewrite the source so spread elements are flattened into explicit calls before reordering.
3. Check enumerateEffectArrayElements output/kind in your tooling to skip non-call entries in the UI.

Example fix

// before
<Sequence effects={[...extraEffects, Spring()]} /> // reorderEffect fromIndex: 0 hits the spread
// after
<Sequence effects={[FadeIn(), Spring()]} /> // reorderEffect fromIndex: 0 hits FadeIn()

const elements = enumerateEffectArrayElements(getEffectsArray(attr));
if (elements[fromIndex].kind !== 'call') {
  throw new TypeError('Source effect is not a call expression');
}

const isCallElement = (
  el: EffectArrayElement,
): el is Extract<EffectArrayElement, {kind: 'call'}> => el.kind === 'call';

try {
  await reorderEffect({input, fromIndex, toIndex, sequenceNodePath});
} catch (e) {
  if (e instanceof Error && e.message.includes('not-call-expression')) {
    // disable reorder UI for this row or flatten spreads first
  } else throw e;
}

When it happens

Trigger: Calling reorderEffect({fromIndex, ...}) where the effects array at that index contains something other than a call expression — e.g. effects={[...(someArray), Spring()]} and fromIndex points at the spread element, or an array hole from sparse literals.

Common situations: Hand-edited JSX where a developer spread an array into effects; generated code that included spreads; sparse arrays; UI showing all indices as draggable including non-call entries.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Cannot delete effect: no effects found
• Cannot reorder effect: target index not-found
• Cannot update effect prop: computed
• Cannot update effect prop
• Could not find as a reorder target

AI-assisted analysis of remotion-dev/remotion@46a3a6bf13 (2026-09-18). Data as JSON: /api/errors/371d2201fd0a11c0. Report an issue: GitHub.

Appendix: source

Thrown at packages/studio-codemods/src/effect-operations.ts:605

		const jsx = getJsx({action: 'reorder', ast, sequenceNodePath});
		const attr = findEffectsAttr(jsx.attributes);
		if (!attr) {
			throw new Error('Could not find effects on the target JSX element');
		}

		const array = getEffectsArray(attr, 'reorder');
		const elements = enumerateEffectArrayElements(array);
		if (fromIndex < 0 || fromIndex >= elements.length) {
			throw new Error('Cannot reorder effect: source index not-found');
		}

		if (toIndex < 0 || toIndex >= elements.length) {
			throw new Error('Cannot reorder effect: target index not-found');
		}

		const target = elements[fromIndex];
		if (target.kind !== 'call') {
			throw new Error(
				'Cannot reorder effect: source effect is not-call-expression',
			);
		}

		trackOpeningElement({jsx, snapshots});
		if (fromIndex !== toIndex) {
			const [moved] = array.elements.splice(fromIndex, 1);
			array.elements.splice(toIndex, 0, moved as never);
		}

		return {
			output: getEffectSourceOutput({
				ast,
				input,
				prettierConfigOverride: prettierConfigOverride ?? null,
				snapshots,
			}),
			formatted: true,

View on GitHub (pinned to 46a3a6bf13)