Add error handling to the Connection state machine

[brentkeller]

Solves

Unexpected errors that occur in the state machine within Connection.ts are not handled and can completely crash a sync server when they're encountered.

Description

This adds a simple error listener when we subscribe to the state machine Actor so that we can at least log the error the host console. This also seems to prevent the hard crash that brings down the running sync server process.

[brentkeller]

@HerbCaudill this implementation seems to be enough to catch errors from the state machine and prevent crashing the sync server. Maybe you have some suggestions at how to do more with the actual error here or how to manage the connection going forward?

[brentkeller]

There are two signatures for the subscribe method, one accepts Observer<T> object and the other accepts listener functions as separate arguments. I've opted for switching to the object signature here because I find it easier to reason about but we could switch to passing multiple functions if we choose.

Docs: https://stately.ai/docs/actors#error-handling
Source: https://github.com/statelyai/xstate/blob/main/packages/core/src/createActor.ts#L322-L350

[brentkeller]

I'm only logging the error to the console here. I'm not sure if it's helpful to also/instead call this.#log.

I also experimented with calling this.stop() here after logging the error to try to force disconnecting this Connection. I don't know if that's appropriate or if there's some better means of disconnecting. Below is a listing of the output around the exception with and without calling stop() for comparison:

Without calling this.stop():

  localfirst:auth:connection:localhost:brent emit change 'connected' +1ms
  localfirst:auth:connection:localhost:brent ⏩ connected  +0ms
  localfirst:auth:connection:localhost:brent emit updated undefined +0ms
  localfirst:auth:connection:localhost admitted device +4ms
Connection encountered an error Error: Device k1ut2gm7y1kqf4was69jm6w3 not found
    at assert (file:///C:/dev/xdev/local-first-auth/packages/shared/dist/index.js:4:19)
    at device (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:699:3)
    at memberByDeviceId (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:891:22)
    at Team.memberByDeviceId (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:1812:12)
    at admit (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:2474:39)
    at file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:2478:24
    at Function.resolveAssign [as resolve] (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\log-a312ebfc.cjs.js:77:21)
    at resolveAndExecuteActionsWithContext (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:2240:56)
    at resolveActionsAndContext (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:2262:21)
    at microstep (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:1987:15)
  localfirst:auth:connection:localhost:brent <-brent #23 SYNC {"head":["3qnkp5bwi8bhv6AH8AMuP77PR2EGvQC8e6ZXB45StY7H"]} +27ms
  localfirst:auth:connection:localhost:brent sending sync message {"head":["3qnkp5bwi8bhv6AH8AMuP77PR2EGvQC8e6ZXB45StY7H"]} +1ms
  localfirst:auth:connection:localhost:brent ->brent #12 SYNC {"head":["3qnkp5bwi8bhv6AH8AMuP77PR2EGvQC8e6ZXB45StY7H"]} +0ms
  localfirst:auth:connection:localhost:brent emit change 'connected' +1ms
  localfirst:auth:connection:localhost:brent ⏩ connected  +0ms
  localfirst:auth:connection:localhost <-? #2 DISCONNECT  +7s

With calling this.stop():

  localfirst:auth:connection:localhost:brent emit change 'connected' +0ms
  localfirst:auth:connection:localhost:brent ⏩ connected  +0ms
  localfirst:auth:connection:localhost:brent emit updated undefined +1ms
  localfirst:auth:connection:localhost admitted device +6ms
Connection encountered an error Error: Device hfppeln7nthulp6nlb1u1jbo not found
    at assert (file:///C:/dev/xdev/local-first-auth/packages/shared/dist/index.js:4:19)
    at device (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:699:3)
    at memberByDeviceId (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:891:22)
    at Team.memberByDeviceId (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:1812:12)
    at admit (file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:2474:39)
    at file:///C:/dev/xdev/local-first-auth/packages/auth/dist/index.js:2478:24
    at Function.resolveAssign [as resolve] (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\log-a312ebfc.cjs.js:77:21)
    at resolveAndExecuteActionsWithContext (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:2240:56)
    at resolveActionsAndContext (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:2262:21)
    at microstep (C:\dev\xdev\local-first-auth\node_modules\.pnpm\[email protected]\node_modules\xstate\dist\raise-182bb5c9.cjs.js:1987:15)
  localfirst:auth:connection:localhost ->? #2 DISCONNECT  +2ms
  localfirst:auth:connection:localhost connection stopped +1ms
  localfirst:auth:connection:localhost:brent <-brent #23 SYNC {"head":["E33dZ6zvXdsA7bfpT3Ebu7jK7wZMBTTsEA7qrnoxtiVD"]} +24ms
  localfirst:auth:connection:localhost:brent sending sync message {"head":["E33dZ6zvXdsA7bfpT3Ebu7jK7wZMBTTsEA7qrnoxtiVD"]} +1ms
  localfirst:auth:connection:localhost:brent ->brent #12 SYNC {"head":["E33dZ6zvXdsA7bfpT3Ebu7jK7wZMBTTsEA7qrnoxtiVD"]} +0ms
  localfirst:auth:connection:localhost:brent emit change 'connected' +1ms
  localfirst:auth:connection:localhost:brent ⏩ connected  +0ms