Error handling seems a little cumbersome (improve DX?)

[harrywebdev]

Consider this example:

import { getError, subscribeError } from "evolu"

// show DB errors
useEffect(() => {
  const notifyOnError = () => {
    const error = getError()
    if (error === null) {
      return
    }

    // use message, if it exists
    if (error.error.type === "UnknownError") {
      // wrap on the error to get to the actual error
      setNotificationMessage(`Error: ${error.error.error.message}`)
    } else {
      setNotificationMessage("Oops, something went wrong.")
    }
  }

  return subscribeError(notifyOnError)
}, [])

Let's look at the types:

export const getError: IO<EvoluError | null> = () => lastErrorRef.read();

export interface EvoluError {
  readonly type: "EvoluError";
  readonly error:
    | TimestampDuplicateNodeError
    | TimestampDriftError
    | TimestampCounterOverflowError
    | TimestampParseError
    | StringMaxLengthError
    | UnknownError
    | SyncError
    | SQLiteError;
}

so the EvoluError is a wrapper and its property error contains the actual error. Now, this error contains various types, ranging from errors without an actual message (their type is the basis for the message) like:

export interface TimestampDuplicateNodeError {
  readonly type: "TimestampDuplicateNodeError";
  readonly node: NodeId;
}

to an unknown error with a message (wrapped under the error property)

export interface UnknownError {
  readonly type: "UnknownError";
  readonly error: TransferableError;
}

interface TransferableError {
  readonly message: string;
  readonly stack: string | undefined;
}

Maybe for production cases, the EvoluError.error.type is enough to produce a feedback message to the user, and the wrap to get a message from UnknownError is good enough for debugging purposes. Maybe, we could do better in how we surface errors - the way I came across this was when I struggled with a correct SQL query and I was getting at the actual DB error message.

[steida]

If you see how it can be improved, describe a solution you would like to see based on your experience.

[steida]

Already fixed