Automattic/mongoose · error · Error

Discriminator with name "${name}" already exists

Error message

Discriminator with name "${name}" already exists

What it means

Error "Discriminator with name "${name}" already exists" thrown in Automattic/mongoose.

Source

Thrown at lib/helpers/model/discriminator.js:261

  // merges base schema into new discriminator schema and sets new type field.
  merge(schema, model.schema);

  if (!model.discriminators) {
    model.discriminators = {};
  }

  if (!model.schema.discriminatorMapping) {
    model.schema.discriminatorMapping = { key: key, value: null, isRoot: true };
  }
  if (!model.schema.discriminators) {
    model.schema.discriminators = {};
  }

  model.schema.discriminators[name] = schema;

  if (model.discriminators[name] && !schema.options.overwriteModels && !overwriteExisting) {
    throw new Error('Discriminator with name "' + name + '" already exists');
  }

  return schema;
};

View on GitHub (pinned to 49cdab0136)

When it happens

Trigger: Thrown at lib/helpers/model/discriminator.js:261 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/7648f49cc25f2a50. Report an issue: GitHub.