fix: use get in constructor for deriveds

[paoloricciuti]

Closes #15288

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Playground

pnpm add https://pkg.pr.new/svelte@15300

[adiguba]

Hello,

I think the $.get() should be wrapped by an untrack(), otherwise this can have fire unwanted effect if the class is created on an effect.

Example here where increment will rebuild a new Foo :

https://svelte.dev/playground/hello-world?version=pr-15300#H4sIAAAAAAAACnVSwW7CMAz9lSgg0Q4E047QVtpl2j-MHUrqsoiQVIkLm6r---KkdBViqtI4z-_Zjp2O6_IMfMvfQSnDrsaqiiVQSYQq5SteSwWObz86jj8N8Qjw-KB6bZq1u4BCwg6lg0e4MBpBow_DMyesbLDY6z3Kc2Msso61Gm0pTqxntTVntojCxY5ItIQqnWNvxrAuQBj_s0upWmA5mzssEZLndMAr0x5UcFRg5QWqBL-kWw_8J_aSUujA9aU5tK1AYxMqPR1TYNAQ5gPRtrs5SGMUrJU5Bs2KTcLfDrGGdBD1t3xSCwtn34zkPlOUL5f3iiMgC66pwgK2Vk_zPpLFGv7VRfdEOKi9oYDmMlx-zyuoy1bhnvsR-a421jQuiXcjZu0nM04hwnOoaxCYMJ89L24FRKKGKw0z9juwe9qyzd_b8F92aBGNZkYLJcUp75I0L3yA9aSFfTEesk3ke3U3kzXVFK6UVfJSUKa8IzFZfbYhcPSG_kV3MO_9sU-REO2R0W1kHZrmXznCN_Ktf0zQf_a_2CIFlFcDAAA=

[paoloricciuti]

Hello,

I think the $.get() should be wrapped by an untrack(), otherwise this can have fire unwanted effect if the class is created on an effect.

Example here where increment will rebuild a new Foo :

https://svelte.dev/playground/hello-world?version=pr-15300#H4sIAAAAAAAACnVSwW7CMAz9lSgg0Q4E047QVtpl2j-MHUrqsoiQVIkLm6r---KkdBViqtI4z-_Zjp2O6_IMfMvfQSnDrsaqiiVQSYQq5SteSwWObz86jj8N8Qjw-KB6bZq1u4BCwg6lg0e4MBpBow_DMyesbLDY6z3Kc2Msso61Gm0pTqxntTVntojCxY5ItIQqnWNvxrAuQBj_s0upWmA5mzssEZLndMAr0x5UcFRg5QWqBL-kWw_8J_aSUujA9aU5tK1AYxMqPR1TYNAQ5gPRtrs5SGMUrJU5Bs2KTcLfDrGGdBD1t3xSCwtn34zkPlOUL5f3iiMgC66pwgK2Vk_zPpLFGv7VRfdEOKi9oYDmMlx-zyuoy1bhnvsR-a421jQuiXcjZu0nM04hwnOoaxCYMJ89L24FRKKGKw0z9juwe9qyzd_b8F92aBGNZkYLJcUp75I0L3yA9aSFfTEesk3ke3U3kzXVFK6UVfJSUKa8IzFZfbYhcPSG_kV3MO_9sU-REO2R0W1kHZrmXznCN_Ktf0zQf_a_2CIFlFcDAAA=

Mh ..I wonder if it should actually be the opposite and we should also track reads to state inside the constructor...effectively you are reading state, why should we assume that you don't want that to be reactive (you can always untrack yourself but if we untrack for you you would have no way of preventing it) 🤔

[adiguba]

I'm not sure about that, but personally I think that constructor should not be reactive on their own value...

I think that's the reason for using .v instead of $.get()

[paoloricciuti]

I'm not sure about that, but personally I think that constructor should not be reactive on their own value...

I think that's the reason for using .v instead of $.get()

I think it was made as an optimization but let me explore this a bit more

[7nik]

Hello,

I think the $.get() should be wrapped by an untrack(), otherwise this can have fire unwanted effect if the class is created on an effect.

Example here where increment will rebuild a new Foo :

https://svelte.dev/playground/hello-world?version=pr-15300#H4sIAAAAAAAACnVSwW7CMAz9lSgg0Q4E047QVtpl2j-MHUrqsoiQVIkLm6r---KkdBViqtI4z-_Zjp2O6_IMfMvfQSnDrsaqiiVQSYQq5SteSwWObz86jj8N8Qjw-KB6bZq1u4BCwg6lg0e4MBpBow_DMyesbLDY6z3Kc2Msso61Gm0pTqxntTVntojCxY5ItIQqnWNvxrAuQBj_s0upWmA5mzssEZLndMAr0x5UcFRg5QWqBL-kWw_8J_aSUujA9aU5tK1AYxMqPR1TYNAQ5gPRtrs5SGMUrJU5Bs2KTcLfDrGGdBD1t3xSCwtn34zkPlOUL5f3iiMgC66pwgK2Vk_zPpLFGv7VRfdEOKi9oYDmMlx-zyuoy1bhnvsR-a421jQuiXcjZu0nM04hwnOoaxCYMJ89L24FRKKGKw0z9juwe9qyzd_b8F92aBGNZkYLJcUp75I0L3yA9aSFfTEesk3ke3U3kzXVFK6UVfJSUKa8IzFZfbYhcPSG_kV3MO_9sU-REO2R0W1kHZrmXznCN_Ktf0zQf_a_2CIFlFcDAAA=

I'd argue - the behavior shouldn't differ from the classless variant. Otherwise it will confuse people.

[paoloricciuti]

I'd argue - the behavior shouldn't differ from the classless variant. Otherwise it will confuse people.

I mean classes are already a bit different but I think I agree with this in this case: and I lean more towards this case because, again, if you want to untrack this by yourself you can, if we untrack for you you can't track it