Do not mark unchanged computed var deps as dirty

[benedikt-bartscher]

part of #4487

[masenf]

one potentially issue i see with this approach is it makes it harder to manually mark a var as dirty, for example if internal change tracking is not working for a certain kind of object, a hackaround was always to assign it to itself to signal to the framework that it should be included in the delta. i know @adhami3310 uses this trick quite a bit.

[benedikt-bartscher]

@masenf I knew this comment was coming 😆

However, I have 2 arguments against it:

• self.var = self.var is not really descriptive and needs a comment to explain what it's doing. self.dirty_vars.add("var"); self._mark_dirty() is pretty descriptive and doesn't need further explanation. We could add a helper which does both in one call.
• Currently, there is no way for users to stop reflex from marking all vars which depend on a computed var as dirty, even if the computed var did not change (_mark_dirty_computed_vars). Maybe I can adjust this PR to only change the computed var behavior?

[benedikt-bartscher]

I just refactored one small repo to always check if the var has changed before assignment. Now I have a diff of 85 lines with repetitive

if self.var != new_var:
  self.var = new_var

[adhami3310]

haven't looked into this too deeply but self.var = self.var is only used to let reflex know about a difference that internal mutability proxy didn't catch

[benedikt-bartscher]

current implementation is not optimal, i have a better one coming
BTW, this PR is now only about unchanged computed vars. I will split #4487 into multiple PRs

[benedikt-bartscher]

need to recheck order of computed var computation