improvement(driver): Differentiate clean vs. abnormal disconnects and emit abnormal disconnects to FRS

[RishhiB]

Today the Routerlicious service receives no signal that a Fluid client disconnected because of an error.

Changes

1. Client side

   • The dispose method in DocumentDeltaConnection is updated to accept an optional error argument. If an error is provided, it indicates an abnormal disconnect.
   • In R11sDocumentDeltaConnection we override disconnectCore.
   • When the client is disconnecting due to an error and the socket is still healthy we emit

     socket.emit("client_disconnect", clientId, documentId, err.errorType);

   • No payload is sent for clean disconnects.

2. Service side

   • server/routerlicious/packages/lambdas/src/nexus/index.ts now listens for the event:

     socket.on("client_disconnect", (clientId, documentId, errorType) => {
         Lumberjack.error(
             "Client disconnected due to error",
             { clientId, documentId, errorType },
             new Error(errorType),
         );
     });

AB#13598
AB#32066

[Copilot]

Pull Request Overview

This PR makes error emission on disconnects optional by introducing an optional error parameter to dispose, disconnect, and disconnectCore, allowing for clean disconnects when no error is provided.

• Added error?: Error to dispose and only pass an IAnyDriverError to disconnect if provided.
• Changed disconnect and disconnectCore signatures to accept an optional err?: IAnyDriverError.
• Updated dispose logic to create and forward an error object only when needed.

Comments suppressed due to low confidence (2)

packages/drivers/driver-base/src/documentDeltaConnection.ts:453

• The @param annotation for disconnectCore is out of sync: it references 'reason' while the parameter is now 'err?: IAnyDriverError'. Please update the JSDoc to reflect the optional parameter name and its purpose.

* @param reason - reason for disconnect

packages/drivers/driver-base/src/documentDeltaConnection.ts:412

• Add unit tests for both clean disconnect (no error) and error-triggered disconnect to verify the optional error logic in dispose and disconnect behaves as intended.

const disconnectError = error

[jason-ha]

}

Looks like a breaking change to IDocumentDeltaConnectionEvents disconnect event

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Refers to: packages/drivers/driver-base/src/documentDeltaConnection.ts:451 in dbdc5b1. [](commit_id = dbdc5b1, deletion_comment = False)