fix: non-null field returning null sometimes triggers TypeError

[bbnjmn]

• fix TypeError: Cannot set properties of null (setting 'fieldName') #208

Bug description

Under some fields resolution timing conditions, non null fields that returns nulls may sometime trigger a TypeError and make a whole query fail.

This happens inremoveBranch function . If we are trying to remove a branch of tree that has already been removed by a non nullable field (a sibling of any ancestor) because it has returned null.

Proposed solution

We can protect us from TypeError by ignoring branches that are no longer part of the tree when calling removeBranch. Error will be preserved and returned back to the client to indicate that a non null field returned a null value (= same behavior as currently).

Note : I’ve split my PR into 2 commits so the first one includes only tests that are failing currently, and the second one actually contains the fix.

[boopathi]

Thank you for your contributions with this PR. I will conduct local testing to understand the bug and its potential effects more thoroughly before continuing with the PR review.

[boopathi]

👍

[bbnjmn]

Hello @boopathi,

How can we make this PR progress as it seems it requires an additional approval ?

Thanks in advance 🙂

[bbnjmn]

@ruiaraujo Can you check this out? Thanks 🙇

[oporkka]

👍

[oporkka]

@bbnjmn thanks for the contribution and sorry to let you wait. I triggered already a new release