When assigning an array of items, none of the items should…

Error message

When assigning an array of items, none of the items should be null or undefined.

What it means

Thrown when an array assigned to a plural linked field through an updatable proxy contains null or undefined items. Relay cannot link a null entry in the store for a plural linked field, so every element of the assigned array must be a valid record object.

Solutions

Filter out null/undefined before assigning: `field.set(items.filter(Boolean))`
Use `items.filter(item => item != null)` to be explicit about both null and undefined
Fix the server/fragment so list items are non-null (e.g. `[Type!]!]`) if nulls should never appear

Example fix

// before
updatable.viewer.friends.set(friends);
// after
updatable.viewer.friends.set(friends.filter(f => f != null));

Defensive patterns

Strategy: validation

Validate before calling

function assertNoNullItems(items) {
  if (items.some(item => item == null)) {
    throw new TypeError('Array assigned to plural linked field contains null/undefined items');
  }
}

Type guard

function hasNoNullItems<T>(items: ReadonlyArray<T | null | undefined>): items is ReadonlyArray<T> {
  return items.every((item): item is T => item != null);
}

Try / catch

try {
  field.set(items);
} catch (e) {
  if (e.message.includes('none of the items should be null')) field.set(items.filter(i => i != null));
  else throw e;
}

Prevention

Filter nulls from GraphQL list results (lists are nullable by default): items.filter(i => i != null)
Request non-null list elements in the schema ([Type!]!]) when possible
Avoid sparse arrays and unfiltered .map results
Validate arrays at the boundary before passing into updaters

When it happens

Trigger: Calling `pluralField.set(items)` where `items` is an array that includes null or undefined elements, e.g. `set([a, null, c])` or an array built from a sparse or nullable-mapped source.

Common situations: Mapping over server data that contains null list items (GraphQL lists are nullable by default); spreading arrays with holes; filtering logic that leaves undefined entries.

Related errors

AI-assisted analysis of facebook/relay@668b1b85e0 (2026-09-02). Data as JSON: /api/errors/110b980721f2842a. Report an issue: GitHub.

Appendix: source

Thrown at packages/relay-runtime/mutations/createUpdatableProxy.js:217

  }
}

function createSetterForPluralLinkedField(
  selection: ReaderLinkedField,
  variables: Variables,
  updatableProxyRootRecord: RecordProxy,
  recordSourceProxy: RecordSourceProxy,
) {
  return function set(newValue: ReadonlyArray<{__id: string, ...}>) {
    const newVariables = getArgumentValues(selection.args ?? [], variables);
    if (newValue == null) {
      throw new Error(
        'Do not assign null to plural linked fields; assign an empty array instead.',
      );
    } else {
      const recordProxies = newValue.map((item): ?RecordProxy => {
        if (item == null) {
          throw new Error(
            'When assigning an array of items, none of the items should be null or undefined.',
          );
        }
        const {__id} = item;
        if (__id == null) {
          throw new Error(
            'The __id field must be present on each item passed to the setter. This indicates a bug in Relay.',
          );
        }
        const newValueRecord = recordSourceProxy.get(__id);
        if (newValueRecord == null) {
          throw new Error(
            `Did not find item with data id ${__id} in the store.`,
          );
        }
        return newValueRecord;
      });
      updatableProxyRootRecord.setLinkedRecords(

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