Inconsistency in clearing state.error in the Advanced Tutorial

[dwiyatci]

Hi again! :)) I noticed that in the Advanced Tutorial, the state.error for issues slice and comments slice are being cleared inconsistently.

• In the issues slice, the state.error is cleared in "fulfilled" reducers:
  https://codesandbox.io/s/rtk-github-issues-example-03-final-ihttc?from-embed=&file=/src/features/issuesList/issuesSlice.ts:1106-1131

• In the comments slice, the state.error is cleared in "pending" and "fulfilled" reducers:
  https://codesandbox.io/s/rtk-github-issues-example-03-final-ihttc?from-embed=&file=/src/features/issueDetails/commentsSlice.ts:535-846

What would be the best place to clear the error state in order to make it consistent when dealing with async requests? Would it be enough to clear it in the "pending" reducers only? 🤔

[akursat]

The "pending" state is about loading not about error.
success:
state.loading = false
state.error = null
failure:
state.loading = false
state.error = payload
pending:
state.loading = true

[dwiyatci]

@akursat Hm yeah, I guess that's one way to look at it. 🙂 But imagine state.error is used to render an error message. Then you would want to clear it as soon as you make a request to the network (as it enters the pending reducer), otherwise the error message will still be shown along with the loading spinner until the network comes back to you with a result (either fulfilled or rejected).

So this formulation may well also be desirable:

pending: (state) => {
  state.loading = true;
  state.error = null;
},
fulfilled: (state) => {
  state.loading = false;
},
rejected: (state, action) => {
  state.loading = false;
  state.error = action.payload;
}

[markerikson]

Obsolete due to #905 .