Attrs are never observed unless added with `@attr` decorator
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 35/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- typescript
Research direction
Start with src/attr.ts, especially defineObservedAttributes() and getAttrNames(), then compare their behavior with the vanilla example in docs/_guide/attrs.md. Confirm whether manually initialized attributes can be observed without @attr; done means the implementation and guide agree on how observed attributes are specified.
Written by the indexing model from the issue text.
Description
Hi folks,
While I was testing the attributes — trying to work my way around #207 — I found another subtle detail. Manually initialized attributes are never observed.
Catalyst's guide provides the following example for vanilla users: https://github.com/github/catalyst/blob/main/docs/_guide/attrs.md#what-about-without-decorators.
Please notice the second argument there defineObservedAttributes(HelloWorldElement, ['foo']) and compare it with the actual function declaration:
https://github.com/github/catalyst/blob/a8fb3ba59a4ac258d0fe64a50ecd3b6997f5f016/src/attr.ts#L99
It doesn't expect the second argument (arguments aren't used either).
Now, internally defineObservedAttributes() pulls attribute names from getAttrNames(), which, in turn, pulls them from attrs (WeakMap). The only way to populate attrs is to use @attr decorator:
https://github.com/github/catalyst/blob/a8fb3ba59a4ac258d0fe64a50ecd3b6997f5f016/src/attr.ts#L15
Maybe I'm missing something, but it seems like there's no way to specify observed attributes without decorators. In any case, it'd be very nice to clarify that 🙂
Thank you!
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