Install anywidget comm provider eagerly

[manzt]

Formatter hooks skip local modules to avoid mistaking user code for third-party packages. Editable installs look local too, so descriptor widgets could open a dummy comm before their formatter ran.

These changes install the lightweight provider during formatter initialization while anywidget itself remains lazy.

Refs MO-6824

[vercel]

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jul 21, 2026 3:53pm

[cubic-dev-ai]

No issues found across 4 files

Architecture diagram

sequenceDiagram
    participant App as Marimo App
    participant Formatters as Formatter Registry
    participant AnywidgetForm as anywidget Formatter
    participant CommProvider as Comm Provider
    participant ImportHook as Import Hook
    participant CommLib as comm Library

    Note over App,CommLib: Formatter Initialization (register_formatters)

    App->>Formatters: register_formatters()
    Formatters->>CommProvider: install_anywidget_comm_provider()
    
    alt anywidget/comm not installed
        CommProvider-->>Formatters: return (no-op)
    else modules available
        CommProvider->>CommLib: Check if already patched
        alt Not patched
            CommProvider->>CommLib: Replace comm.create_comm with marimo wrapper
            CommLib-->>CommProvider: Patched
        else Already patched
            CommProvider->>CommProvider: Skip (idempotent)
        end
    end

    Note over Formatters,CommLib: Later: Import Hook Triggers

    App->>ImportHook: Import anywidget module
    ImportHook->>AnywidgetForm: Register formatter for AnyWidget class
    Note over AnywidgetForm,CommLib: At this point, comm provider is already installed
    
    Note over App,CommLib: Widget Instantiation (Descriptor-based anywidget)

    App->>CommLib: Create comm (descriptor widget init)
    alt anywidget comm (target="jupyter.widget", model_module="anywidget")
        CommLib->>CommLib: Create marimo-backed comm
        CommLib-->>App: MarimoComm instance
    else non-anywidget comm
        CommLib->>CommLib: Create DummyComm (no-op)
        CommLib-->>App: DummyComm instance
    end

    Note over App,CommLib: Formatter Execution (for display)

    App->>Formatters: Format widget for display
    Formatters->>AnywidgetForm: Get HTML representation
    AnywidgetForm-->>Formatters: MIME bundle
    Formatters-->>App: Formatted output

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