Function legacyTraitError

legacyTraitError(
    item:
        | undefined
        | null
        | {
            _source?: { type?: string };
            id?: string;
            name?: string;
            type?: string;
        },
): string
| null
Build the "unrecognized retired type" error message for a single document, or null when the document is not a legacy trait (#651). Pure and Foundry-free so it can be unit-tested.

The trait item type was retired and is deliberately not auto-converted: a surviving trait document is flagged as unrecognized so the GM resolves it by hand (delete it, or recreate the data as a trauma/attribute), never silently transformed or deleted by the system.

A legacy trait is detected by its stored type on either type (Foundry keeps the type) or _source.type (Foundry fell the document back to base but preserved the original type in its source) — so the check fires whichever way the client loads an unregistered-type document.
Parameters
- item:
      | undefined
      | null
      | {
          _source?: { type?: string };
          id?: string;
          name?: string;
          type?: string;
      }
  The document to check (its stored type / _source.type, plus name / id for the message).
Returns string | null
The error message, or null when item is not a retired trait.
- Defined in src/core/foundry/migration.ts:68