Only set model_parameters once

[Corvince]

Summary

While working on a seed widget I saw a major bug in solara viz. Model_parameters get reset on every model reset. This is pretty serious and I think we need another bug release soon.

Bug / Issue

Describe the bug
Hitting "reset" in the ui resets the model, but also resets the model_parameters to their initial value.

To Reproduce
Run Schelling example. Reduce agent density. Hit reset. Works as expected. Hit reset again. Density is now restored.

Implementation

Use solaras use_effect to initialize model_parameters only once.

screen-capture.webm

[quaquel]

Would there be a way to test this behavior as part of our unit tests?

[quaquel]

That is a serious bug and something that had been nagging me but did not investigate yet. Great you spotted it and fixed it.

I will put some effort on the logging stuff because that would have helped in spotting this earlier.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🟢 -9.4% [-10.9%, -7.9%]	🔵 -0.1% [-0.2%, +0.1%]
BoltzmannWealth	large	🔵 +1.1% [+0.8%, +1.4%]	🔵 +0.9% [+0.3%, +1.6%]
Schelling	small	🔵 +0.6% [+0.1%, +1.0%]	🔵 -0.9% [-1.2%, -0.7%]
Schelling	large	🔵 +1.1% [+0.6%, +1.5%]	🔵 -0.2% [-1.8%, +2.0%]
WolfSheep	small	🔵 +2.5% [+2.1%, +2.9%]	🔵 +0.6% [+0.3%, +0.8%]
WolfSheep	large	🔵 +1.7% [+0.6%, +3.1%]	🔵 +0.9% [-2.1%, +5.0%]
BoidFlockers	small	🔵 +0.3% [-0.2%, +0.9%]	🔵 +0.3% [-0.4%, +1.0%]
BoidFlockers	large	🔵 +0.4% [-0.2%, +1.1%]	🔵 -0.1% [-0.7%, +0.5%]

[EwoutH]

Thanks for catching it and fixing it. I will do a backport + release as soon as you merge.

Anything else we'll want to include in the backport?

[Corvince]

Would there be a way to test this behavior as part of our unit tests?

Not right now, at least not in an easy way. This would require a integration test that combined solara viz, ModelController and ModelCreator. We don't have that yet

[EwoutH]

3.0.3 with this fix is released.