What causes "Schematic "${name}" is missing fields." in angular/angular-cli?

Add a `description` field to the schematic entry in collection.json.

angular/angular-cli · error · SchematicMissingFieldsException

Schematic "${name}" is missing fields.

Error message

Schematic "${name}" is missing fields.

What it means

Thrown by _transformSchematicDescription when a schematic's resolved description lacks required fields: factoryFn, path, or description. After resolving the factory reference, these three fields must all be populated for the schematic to run.

Source

Thrown at packages/angular_devkit/schematics/tools/file-system-engine-host.ts:84

    desc: Partial<FileSystemCollectionDesc>,
  ): FileSystemCollectionDesc {
    if (!desc.schematics || typeof desc.schematics != 'object') {
      throw new CollectionMissingSchematicsMapException(name);
    }

    return {
      ...desc,
      name,
    } as FileSystemCollectionDesc;
  }

  protected _transformSchematicDescription(
    name: string,
    _collection: FileSystemCollectionDesc,
    desc: Partial<FileSystemSchematicDesc>,
  ): FileSystemSchematicDesc {
    if (!desc.factoryFn || !desc.path || !desc.description) {
      throw new SchematicMissingFieldsException(name);
    }

    return desc as FileSystemSchematicDesc;
  }

  override hasTaskExecutor(name: string): boolean {
    if (super.hasTaskExecutor(name)) {
      return true;
    }

    try {
      const maybePath = require.resolve(join(this._root, name));
      if (existsSync(maybePath)) {
        return true;
      }
    } catch {}

    return false;

View on GitHub (pinned to bb72145f9a)

Solutions

Add a `description` field to the schematic entry in collection.json.
Verify the `factory` reference resolves to an existing file so `path` and `factoryFn` get populated.
If subclassing the host, ensure the partial description passed to _transformSchematicDescription includes factoryFn, path, and description.

Example fix

// before (collection.json)
"my-schematic": { "factory": "./index#run" }
// after
"my-schematic": { "factory": "./index#run", "description": "Generates my thing" }

Defensive patterns

Strategy: validation

Validate before calling

const coll = JSON.parse(readFileSync('collection.json', 'utf8'));
for (const [name, s] of Object.entries(coll.schematics)) {
  if (!s.factory) throw new Error(`'${name}' missing factory`);
  if (!s.description) throw new Error(`'${name}' missing description (required by FileSystemEngineHost)`);
}

Try / catch

try {
  const schematic = collection.createSchematic(name, true);
} catch (e) {
  if (String(e.message).includes('is missing fields')) {
    console.error("Add description (and verify factory resolves so path/factoryFn are set)");
  } else throw e;
}

Prevention

Always include factory, description, and (when used) schema in every schematic entry.
Validate collection.json against the official JSON schema in CI.
Keep factory paths stable across refactors; add a load-all-schematics smoke test.

When it happens

Trigger: A collection.json schematic entry missing `description` while having a factory (factoryFn and path come from resolution); or a factory module that resolves but the pipeline cannot derive path/description — `if (!desc.factoryFn || !desc.path || !desc.description)` triggers.

Common situations: Minimal hand-written collection.json entries that omit `description`; factory files that were moved so `path` cannot be derived; partially-filled schematic objects in custom engine subclasses calling _transformSchematicDescription with incomplete partials.

Related errors

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/c5b57c5473600840. Report an issue: GitHub.