fix: enum comparisons in module reloading

[mscolnick]

Fixes #9808

When a module containing an enum.Enum was reloaded, dependent modules that had already imported the enum (e.g. via from enums import Fruits) kept references to the old enum class, while re-imported symbols pointed at the new class. Enum members from different class objects do not compare equal, so functions like is_orange(Fruits.ORANGE) incorrectly returned False after reload even when the enum definition was unchanged.

superreload now restores updated old objects into the reloaded module's namespace after patching, so dependent modules and re-imports continue to share the same class/function instances.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jun 11, 2026 6:14pm

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="marimo/_runtime/reload/autoreload.py">

<violation number="1" location="marimo/_runtime/reload/autoreload.py:573">
P1: The new namespace rebinding restores stale objects even when `update_generic` cannot update them, so unsupported module attributes can be reverted to pre-reload state.</violation>
</file>

Architecture diagram

sequenceDiagram
    participant User as User Kernel
    participant Reloader as ModuleReloader
    participant SysMod as sys.modules
    participant DepMod as Dependent Module
    participant EnumMod as Enum Module

    Note over User,EnumMod: Runtime Module Reload Flow

    User->>Reloader: check(modules, reload=True)
    Reloader->>Reloader: superreload() begins
    
    loop For each changed name in enum module
        Reloader->>SysMod: Get old object references
        SysMod-->>Reloader: old_refs (weak references)
        Reloader->>Reloader: update_generic(old_obj, new_obj)
        Note over Reloader: Patch old object to match new,<br/>preserving object identity
        Reloader->>EnumMod: Keep updated old object in __dict__
        Note over Reloader,EnumMod: NEW: Overwrite module namespace<br/>so that imported names point to<br/>the patched old instance
        EnumMod-->>EnumMod: module.__dict__[name] = old_obj
    end

    Note over DepMod: Dependent module already imported<br/>via `from enums import Fruits`

    DepMod-->>DepMod: Fruits refers to patched old class
    EnumMod-->>EnumMod: Fruits also refers to same patched old class
    
    User->>DepMod: call is_orange(Fruits.ORANGE)
    DepMod->>DepMod: fruit == Fruits.ORANGE
    
    alt Same object identity
        Note over DepMod: Both Fruits classes are<br/>the same patched instance
        DepMod-->>User: True (correct)
    else Different objects (without fix)
        Note over DepMod: Fruits.ORANGE from different<br/>class objects don't compare equal
        DepMod-->>User: False (bug)
    end

    Note over DepMod,EnumMod: Both modules now share same<br/>class/function instances after reload

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Re-trigger cubic</sub>

[cubic-dev-ai]

P1: The new namespace rebinding restores stale objects even when update_generic cannot update them, so unsupported module attributes can be reverted to pre-reload state.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At marimo/_runtime/reload/autoreload.py, line 573:

<comment>The new namespace rebinding restores stale objects even when `update_generic` cannot update them, so unsupported module attributes can be reverted to pre-reload state.</comment>

<file context>
@@ -558,12 +558,20 @@ def superreload(
+        # Keep the updated old object in the module namespace so that
+        # dependent modules (e.g. `from enums import Fruits`) still refer
+        # to the same class/function instances after reload.
+        if kept_old_obj is not None:
+            module.__dict__[name] = kept_old_obj
 
</file context>