computed properties are re-evaluating more often than expected

[indirectlylit]

Version

2.5.16

Reproduction link

https://jsfiddle.net/eywraw8t/193744/

Steps to reproduce

• Create some data A and computed props B and C
• Let C depend on B, and B depend on A. Set it up so the value of B should change less often than A
• Then modify A

What is expected?

The value of C should only be re-computed when the value of B changes, independent of how often A is changing.

What is actually happening?

The value of C is re-computed whenever A changes. This results in many extra re-computations.

---

The docs say:

A computed property will only re-evaluate when some of its dependencies have changed.

In this case, I thought there was a bug in my code because certain threshold-based computed properties were triggering re-computes far more often than expected, and some of these re-computes were fairly expensive.

Perhaps is expected behavior? However it was surprising to me, and negates a lot of the potential for cache-based optimization when leveraging computed props.

Compare to this implementation that uses watchers and extra data, but works as expected:

https://jsfiddle.net/eywraw8t/193746/

Here, C is only recomputed when B changes - not whenever A changes.

[sqal]

seems to be fixed in 2.5.17-beta.0

[indirectlylit]

seems to be fixed in 2.5.17-beta.0

note - reverted and not released due to regressions

[zfeher]

We also ran into a similar issue today.

When can we expect the fix to be released for this?

We can't use the v2.5.17-beta.0 because some things broke when we tried it so we reverted back to 2.5.16. This problem can cause some headaches, would be nice to have the fix released.

[Justineo]

Duplicate of #7767