fix: properly initialize rx.Field annotated backend vars in mixin states

[benedikt-bartscher]

Now I remember what "multiple issues" meant in #5629

[codspeed-hq]

CodSpeed Performance Report

Merging #5909 will create unknown performance changes

_{Comparing benedikt-bartscher:fix-rx-field-annotated-backend-vars-in-mixin-states (ee35403) with main (fb19fb4)}

Summary

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⏩ 8 skipped¹

Footnotes

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[greptile-apps]

Greptile Overview

Summary

Fixed backend variable initialization for mixin states when using rx.Field annotations by consolidating collection logic to properly unwrap Field objects.

• Previously, backend vars from mixins with rx.Field were processed in a separate loop that used copy.deepcopy(), which incorrectly stored the Field object itself instead of calling default_value() to extract the actual default value
• Now backend vars from all mixins are collected upfront in the same comprehension that handles the main class, ensuring Field objects are properly unwrapped via value.default_value()
• Also fixes is_backend_base_variable() to receive mixin_cls instead of cls, which correctly handles name-mangled private attributes specific to each mixin class
• Removes 3 lines of redundant mixin backend var processing that was causing the bug

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The fix consolidates backend var initialization logic and eliminates a clear bug where Field objects were incorrectly deep-copied instead of unwrapped. The change follows the existing pattern used for the main class and aligns with how computed vars from mixins are already handled. No edge cases or breaking changes identified.
• No files require special attention

Important Files Changed

File Analysis

Filename	Score	Overview
reflex/state.py	5/5	Fixes proper initialization of rx.Field annotated backend vars in mixin states by collecting them upfront with correct Field unwrapping instead of deep copying them later

Sequence Diagram

sequenceDiagram
    participant C as Class.__init_subclass__
    participant M as Mixin Classes
    participant BV as Backend Vars Collection
    participant F as Field Objects

    C->>M: Get _mixins()
    Note over C,M: Returns list of mixin classes
    
    C->>BV: Collect backend vars from mixins + cls
    loop For each mixin_cls in [*mixins, cls]
        BV->>M: Get __dict__.items()
        BV->>BV: Check is_backend_base_variable(name, mixin_cls)
        alt Value is Field object
            BV->>F: value.default_value()
            F-->>BV: Return unwrapped default
        else Value is not Field
            BV->>BV: Use value directly
        end
    end
    
    C->>BV: Update with annotated backend vars
    loop For each mixin_cls in [*mixins, cls]
        BV->>M: Get _get_type_hints().items()
        BV->>BV: Check if not in new_backend_vars
        BV->>C: cls._get_var_default(name, annotation)
        C-->>BV: Return default value
    end
    
    C->>C: Merge inherited + new backend vars
    Note over C: cls.backend_vars = {**inherited, **new}

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