emberjs/ember.js · error · Error

Assertion Failed: ${desc}

Error message

Assertion Failed: ${desc}

What it means

Ember's assert() (from @ember/debug) throws an Error with the message 'Assertion Failed: <desc>' when its second argument is falsy. It is Ember's internal way to surface invariant violations in framework code and in apps during development.

Source

Thrown at packages/@ember/debug/lib/assert.ts:54

    // Fail unconditionally
    assert('This code path should never be run');
    ```

    @method assert
    @static
    @for @ember/debug
    @param {String} description Describes the expectation. This will become the
      text of the Error thrown if the assertion fails.
    @param {any} condition Must be truthy for the assertion to pass. If
      falsy, an exception will be thrown.
    @public
    @since 1.0.0
  */
  function assert(desc: string): never;
  function assert(desc: string, test: unknown): asserts test;
  function assert(desc: string, test?: unknown): asserts test {
    if (!test) {
      throw new Error(`Assertion Failed: ${desc}`);
    }
  }
  setAssert(assert);
}

View on GitHub (pinned to 26f97246a8)

Solutions

1. Read the desc after 'Assertion Failed:' to identify the violated invariant
2. Fix the condition the assertion checks (supply the missing value / correct the call)
3. Search Ember source or the failing addon for the assert to understand the contract

Example fix

// before
this.set('controller', getOwner(this).lookup('controller:missing'));
// after
let controller = getOwner(this).lookup('controller:missing');
assert('Expected controller:missing to be registered', controller);
this.set('controller', controller);

// validate the invariant before the call that asserts it
assert('model must be loaded', model != null);

function hasModel(obj) { return obj != null && typeof obj === 'object'; }

try { riskyOperation(); } catch (e) { if (!/^Assertion Failed:/.test(e.message)) throw e; handleInvariantViolation(e.message.replace('Assertion Failed: ', '')); }

When it happens

Trigger: Any internal or app-level call to assert(desc, condition) where condition is falsy — e.g. assert('must have a model', this.model).

Common situations: Framework invariant violations during upgrade (removed/renamed APIs), passing undefined where a required value is expected, misconfigured initializers.

Related errors

• deprecation override for ${id} not found
• BUG: owner is missing renderer
• You must pass both the owner and args to super() in your com
• You must pass both the owner and args to super() in your com
• Cannot call `.lookup('${fullName}')` after the owner has bee

AI-assisted analysis of emberjs/ember.js@26f97246a8 (2026-09-01). Data as JSON: /api/errors/3e6b32699b000d5c. Report an issue: GitHub.