Foundry376/Mailspring · error · Error

Validation failed at ${keyPath}, ${JSON.stringify(value)} mu

Error message

Validation failed at ${keyPath}, ${JSON.stringify(value)} must be null

What it means

Config schema enforcer for type 'null': the value is neither undefined nor null, but the schema declares this key must be null. In practice the enforcer is only reached when a schema pins a key to null; any concrete value fails. Note that coercing null-ish values just unsets the key.

Source

Thrown at app/src/config.ts:829

    },
  },

  string: {
    validate(keyPath, value, schema) {
      if (typeof value !== 'string') {
        throw new Error(
          `Validation failed at ${keyPath}, ${JSON.stringify(value)} must be a string`
        );
      }
      return value;
    },
  },

  null: {
    // null sort of isnt supported. It will just unset in this case
    coerce(keyPath, value, schema) {
      if (![undefined, null].includes(value)) {
        throw new Error(`Validation failed at ${keyPath}, ${JSON.stringify(value)} must be null`);
      }
      return value;
    },
  },

  object: {
    coerce(keyPath, value, schema) {
      if (!isPlainObject(value)) {
        throw new Error(
          `Validation failed at ${keyPath}, ${JSON.stringify(value)} must be an object`
        );
      }
      if (schema.properties == null) {
        return value;
      }

      const newValue = {};
      for (const prop in value) {

View on GitHub (pinned to 648c685d60)

Solutions

1. Unset the key entirely instead of assigning a value to a null-typed setting
2. Remove the null-typed schema entry if the key is meant to hold data

When it happens

Trigger: Thrown at app/src/config.ts:829 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/35139dd6b152ca1c. Report an issue: GitHub.