Automattic/mongoose · error · Error

`$expr` must be an object or boolean literal

Error message

`$expr` must be an object or boolean literal

What it means

Error "`$expr` must be an object or boolean literal" thrown in Automattic/mongoose.

Source

Thrown at lib/helpers/query/cast$expr.js:76

  '$week',
  '$dayOfMonth',
  '$dayOfYear',
  '$hour',
  '$minute',
  '$second',
  '$isoDayOfWeek',
  '$isoWeekYear',
  '$isoWeek',
  '$millisecond'
]);
const expressionOperator = new Set(['$not']);

module.exports = function cast$expr(val, schema, strictQuery) {
  if (typeof val === 'boolean') {
    return val;
  }
  if (typeof val !== 'object' || val === null) {
    throw new Error('`$expr` must be an object or boolean literal');
  }

  return _castExpression(val, schema, strictQuery);
};

function _castExpression(val, schema, strictQuery) {
  // Preserve the value if it represents a path or if it's null
  if (isPath(val) || val === null) {
    return val;
  }

  if (val.$cond != null) {
    if (Array.isArray(val.$cond)) {
      val.$cond = val.$cond.map(expr => _castExpression(expr, schema, strictQuery));
    } else {
      val.$cond.if = _castExpression(val.$cond.if, schema, strictQuery);
      val.$cond.then = _castExpression(val.$cond.then, schema, strictQuery);
      val.$cond.else = _castExpression(val.$cond.else, schema, strictQuery);

View on GitHub (pinned to 49cdab0136)

When it happens

Trigger: Thrown at lib/helpers/query/cast$expr.js:76 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Automattic/mongoose@49cdab0136 (2026-08-21). Data as JSON: /api/errors/9e302b688e400a88. Report an issue: GitHub.