[Bug]: Gracefully handle unknown (unavailable) entities - when state object is missing in hass.states

[kulmegil]

Current Behavior

When entity state is not available in hass.states lot's of JS errors are spammed. This can happen when e.g.

• "legacy" integration fails to setup entity without uniqueId (read-only entity).
• user changed entity_id without performing changes to lovelace config.

Card is not rendered.

Expected Behavior

Gracefully handle situation without throwing JS errors.

Render empty "unavailable" card (e.g. using entity_id as primary text). Or display "error card".

Steps To Reproduce

1. Create any mushroom card related to an entity
2. Set entity_id to non existing entity (or change entity_ids after creating card)

Environment

- OS: Windows / Android
- Browser: Chrome / Firefox / native app
- Version: any
- Hassio: 2022.7

Anything else?

[areyoufserious]

This issue significantly affects frontend performance

[KTibow]

I'm working on a fix. How should this be handled?

1. Make the card be nothing
2. Pretend the entity has an unknown state
3. Make a custom error card to show in place of it

[piitaya]

It think just render null is enough for now. It's already the case but maybe there is some missing checks.

[KTibow]

https://github.com/piitaya/lovelace-mushroom/blob/588a9ea5c74ae527c35dadde4d4e474fb24e6d02/src/cards/entity-card/entity-card.ts#L81-L84 If the entity doesn't exist, it tries to get attributes, which is null, so it does null.friendly_name.

[shbatm]

Any update on this, just recently came across what looks to be the same issue; happy to test or support if needed.