Apollo-client: Query onCompleted callback is not called when the query data updates due to a cache update

[dobesv]

When trying to upgrade from react-apollo 2.5.8 to 3.1.5 we found that the behavior of the onCompleted callback on the Query component had changed in a breaking manner.

Intended outcome:

A Query components onCompleted callback should be called any time the data for that Query changes, even if the change is made by another operation such as a mutation or a cache update.

Actual outcome:

The onCompleted callback might not be called if changes are made to the cache that affect the query data.

How to reproduce the issue:

I made a reproduction of this behavior in this branch here:

https://github.com/dobesv/react-apollo-error-template/tree/query-oncomplete-bug

If you open the console you will see that the onCompleted function logs only on the initial load, if you click the button it does not log that any more.

If you rollback to the older version using npm i [email protected] and restart the app, clicking the button logs onCompleted on every click.

Versions

  System:
    OS: Linux 5.0 Linux Mint 19 (Tara)
  Binaries:
    Node: 12.13.1 - ~/.nvm/versions/node/v12.13.1/bin/node
    Yarn: 1.19.0 - /usr/bin/yarn
    npm: 6.12.1 - ~/.nvm/versions/node/v12.13.1/bin/npm
  Browsers:
    Chrome: 77.0.3865.90
    Firefox: 76.0
  npmPackages:
    apollo-cache-inmemory: ^1.6.6 => 1.6.6 
    apollo-client: 2.6.10 => 2.6.10 
    react-apollo: 3.1.5 => 3.1.5 

Workaround

Instead of using onCompleted to detect changes, you could do the same code in the children render prop. This might be called more often than onCompleted would have been called, but in many cases it probably won't be a serious performance concern. Note that if you use setState in your handler you may have to add a setTimeout and make sure you do not call setState again if the value hasn't changed, to avoid infinite setState -> render loops.

[unutoiul]

same issue heree

[dobesv]

@unutoiul Can you use the "emoji" button to add a "thumbs up" instead of adding a "me too" comment? That seems to be the preferred etiquette for "me too" on github these days, and makes it easier for people to count up the responses.

[unutoiul]

Loool thanks Buddy, did I think the issue?

[andrewnaeve]

@dobesv Can you confirm this codesandbox is a repro of the issue you're experiencing?

https://codesandbox.io/s/compassionate-golick-5042m?file=/src/App.tsx

[dobesv]

@andrewnaeve It looks that way to me, yes.

[natalieytan]

Is it possible to confirm if this is a bug or intended behaviour?

On the other hand I am investigating how to perform a side-effect on the first successful network call, and not on subsequent cache updates.

If this is the intended behaviour of onComplete, it looks like it would suit my purposes.

If it is not the intended behaviour (and the behaviour will change on version bump), I will have to find alternatives.