Declarative Component State vs. Runtime State for Schema Evolution

Direct answer

Do not rely solely on declarative component re-initialization for schema evolution. Re-initialization restores definition-level defaults; it does not transform previously persisted runtime state. Use explicit browser storage keyed by a schema version, hydrate after the component mounts, and run migrations before rendering depends on the state.

Likely explanation versus confirmed facts

Likely explanation (verify against your PyScript release): PyScript bootstraps custom elements when the page loads. Lifecycle hooks run when the element is created or connected. A full page reload re-runs initialization from scratch, but re-injecting <py-script> on the same page does not automatically remount existing component instances. Hook names differ across PyScript versions.

Confirmed facts: Browser storage is same-origin only. localStorage and sessionStorage are synchronous and string-based. PyScript's browser runtime has no documented built-in component schema versioning or automatic migration, so version validation and migration logic must be application code.

Steps for this case

1. Persist component state under a key that includes a schema version, for example pyscript-component-v1.
2. On component mount, read the stored value. If absent or unreadable, initialize from the component definition: property defaults, parsed attributes, constructor arguments, and template data.
3. If present, compare the stored schema version against the current definition. Run migration functions for intermediate versions, reject unknown fields, and fall back to defaults when migration fails.
4. Use sessionStorage when state only needs to survive within one tab. Use localStorage or IndexedDB for longer persistence; prefer IndexedDB for large or complex state because it is asynchronous.
5. Never store secrets or unversioned blobs in browser storage. Design for missing storage and private browsing by falling back to definition defaults.

Verification

• Open DevTools, log component initialization and storage reads on reload. Confirm initialization runs once per element and defaults apply when storage is absent.
• Change the stored schema version or corrupt a stored value, reload, and confirm migration runs or the component falls back to defaults without crashing.
• Call customElements.whenDefined('your-tag') and inspect the stored key before and after reload to distinguish in-memory reset from persisted hydration.

Missing diagnostic detail: Which PyScript version are you targeting? Lifecycle hook names and component APIs differ across releases, so the exact mount hook to use for hydration cannot be confirmed without it.

Assumptions and uncertainty: This answer treats the research brief as planning context, not verified evidence. The absence of built-in PyScript schema versioning and the behavior of same-page <py-script> re-injection should be confirmed against your installed release before production use.