Function formatError

test/utils.ts:311–329

(errors: ParsingDiagnostic[])

  return [
    'Error',
    [
      'String',
      ...(errors.map((x) => {
        // If we have an array as the last element, it's the trace. Remove it.
        if (
          Array.isArray(x.message) &&
          Array.isArray(x.message[x.message.length - 1])
        ) {
          return x.message.slice(0, -1);
        }

        return x.message;
      }) as Expression[]),
    ],
  ];
}

export function validEpsil(s: string): Expression | null {
  const [value, errors] = parseEpsil(s);
  if (errors && errors.length > 0) return formatError(errors);
  return strip(value);
}