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Preferences ​

Origin ​

Customer reported the breadcrumbs segmented control appeared unselected on launch. Root cause: localStorage contained a stale enum value from an older app version that no longer matched any valid T_Breadcrumbs member. The ?? default fallback only catches null/undefined — not invalid values.

Solution ​

Enum validation system in Enumerations.ts:

Enum_Spec class ​

typescript
export class Enum_Spec {
    constructor(public enum_type: object | null, public defaultValue: any) {}
}

Centralized defaults dictionary ​

typescript
export const spec_dict_byType: Enum_Spec_ByType = {
    [T_Preference.breadcrumbs]:     new Enum_Spec(T_Breadcrumbs,       T_Breadcrumbs.focus),
    [T_Preference.paging_style]:    new Enum_Spec(T_Cluster_Pager,     T_Cluster_Pager.sliders),
    [T_Preference.graph]:           new Enum_Spec(T_Graph,             T_Graph.tree),
    [T_Preference.focus]:           new Enum_Spec(T_Focus,             T_Focus.dynamic),
    // ... etc
};

Helper for writable defaults ​

typescript
export const def = (key: T_Preference): any => spec_dict_byType[key]?.defaultValue ?? null;

Validating read_key ​

typescript
read_key(key: T_Preference): any {
    const spec   = spec_dict_byType[key];
    const stored = this.get_forKey(key);
    if (stored !== null) {
        if (!spec || !spec.enum_type) {
            return stored;  // no validation for non-enum prefs
        }
        if (Object.values(spec.enum_type).includes(stored)) {
            return stored;  // valid enum value
        }
    }
    // invalid or missing: reset to default
    const defaultValue = spec?.defaultValue ?? null;
    if (defaultValue !== null) {
        this.write_key(key, defaultValue);
    }
    return defaultValue;
}

Single source of truth ​

Visibility.ts writables use def():

typescript
const P = T_Preference;
w_t_breadcrumbs = writable<T_Breadcrumbs>(def(P.breadcrumbs));
w_t_focus       = writable<T_Focus>(def(P.focus));

Files ​

  • Enumerations.ts — Enum_Spec, spec_dict_byType, def()
  • Preferences.ts — read_key() with validation
  • Visibility.ts — writable initializers use def(P.key)