Foundry376/Mailspring · error

Menu parent did not return an itemKey for item

Error message

Menu parent did not return an itemKey for item

What it means

Warning while rendering Menu items: the parent's itemKey prop returned a falsy key (undefined/'') for an item, so React has no stable identity for the row and selection state (selectedItemKey) cannot round-trip. The menu still renders, but keyboard selection and highlighting misbehave.

Source

Thrown at app/src/components/menu.tsx:405

    const items = (this.props.items || []).map((item, i) => {
      const content = this.props.itemContent(item);
      if (React.isValidElement(content) && content.type === MenuItem) {
        return content;
      }

      const onMouseDown = (event: React.MouseEvent<HTMLDivElement>) => {
        event.preventDefault();
        const key = this.props.itemKey(item);
        this.setState({ selectedIndex: i, selectedItemKey: key });
        if (this.props.onSelect) {
          return this.props.onSelect(item);
        }
      };

      const key = this.props.itemKey(item);
      if (!key) {
        console.warn('Menu parent did not return an itemKey for item', item);
      }
      if (seenItemKeys[key]) {
        console.warn({ 'Menu items have colliding keys': item }, seenItemKeys[key]);
      }
      seenItemKeys[key] = item;

      return (
        <MenuItem
          key={key}
          id={this.props.listboxId ? `${this.props.listboxId}-option-${key}` : undefined}
          role={this.props.listboxId ? 'option' : undefined}
          onMouseDown={onMouseDown}
          checked={this.props.itemChecked && this.props.itemChecked(item)}
          content={content}
          selected={this.state.selectedIndex === i}
          suppressAriaSelected={!!this.props.onActiveDescendantChange}
        />
      );

View on GitHub (pinned to 648c685d60)

Solutions

1. Fix the itemKey callback to return a unique non-empty string/id for every item
2. Filter out empty placeholder items before passing them to Menu

When it happens

Trigger: Thrown at app/src/components/menu.tsx:405 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Foundry376/Mailspring@648c685d60 (2026-09-03). Data as JSON: /api/errors/22ec1af86a9f0bdd. Report an issue: GitHub.