Foundry376/Mailspring · error

onRequestCompletions returned an invalid type. It must retur

Error message

onRequestCompletions returned an invalid type. It must return an Array of tokens or a Promise that resolves to an array of tokens

What it means

Contract warning in TokenizingTextField._refreshCompletions: the onRequestCompletions prop returned neither an array nor a Promise (e.g. undefined or an object), so autocomplete completions cannot be populated and the completion dropdown stays empty/broken for that input.

Source

Thrown at app/src/components/tokenizing-text-field.tsx:865

  _refreshCompletions = (val = this.state.inputValue, { clear }: { clear?: boolean } = {}) => {
    const usedKeys = this.props.tokens.map(this.props.tokenKey);
    const removeUsedTokens = (tokens) => {
      return tokens.filter((t) => !usedKeys.includes(this.props.tokenKey(t)));
    };

    const tokensOrPromise = this.props.onRequestCompletions(val, { clear });

    if (_.isArray(tokensOrPromise)) {
      this.setState({ completions: removeUsedTokens(tokensOrPromise) });
    } else if (tokensOrPromise instanceof Promise) {
      tokensOrPromise.then((tokens) => {
        if (!this._mounted) {
          return;
        }
        this.setState({ completions: removeUsedTokens(tokens) });
      });
    } else {
      console.warn(
        'onRequestCompletions returned an invalid type. It must return an Array of tokens or a Promise that resolves to an array of tokens'
      );
      this.setState({ completions: [] });
    }
  };

  // Rendering

  _completionsId() {
    return `${this._inputId}-completions`;
  }

  _valueDescriptionId() {
    return `${this._inputId}-value`;
  }

  _onActiveDescendantChange = (id: string | null) => {
    this.setState({ activeDescendantId: id });

View on GitHub (pinned to 648c685d60)

Solutions

1. Fix the consumer's onRequestCompletions to return an Array of tokens or a Promise resolving to one
2. Return an empty array instead of undefined when there are no completions

When it happens

Trigger: Thrown at app/src/components/tokenizing-text-field.tsx:865 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/7ebc0ad12cb2ba01. Report an issue: GitHub.