Fix issue where selection set flattening uses the wrong parent type

[jdmoody]

Description

Related #7364 and #6874

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Screenshots/Sandbox (if appropriate/relevant):

Here's a screenshot of how the test fails without the bugfix:

How Has This Been Tested?

• I created a new unit test in ts-documents.spec.ts that fails before the fix and succeeds afterwards.
• I plan on testing this on a codebase with a large schema. I'll update this comment when I have verified it works on our codebase.

Checklist:

• I have followed the CONTRIBUTING doc and the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Further comments

This is just #6874 with a unit test to show what has been fixed 😅 @mvestergaard did all the hard work here

The important features of the schema and query used in the test are:

• The snake field returns a SnakeResult and all the child fields are within a ... on Snake inline fragment with a type condition. (I tried having the snake field return a type Snake, instead, but this did not cause a bug)
• The Bat and Snake subtypes of Animal both have a field named features, but they are of a different type.

There might be other test cases that cause the same error because what @cecchi described in #7364 seems to be slightly different than the issue I was able to repro.

[changeset-bot]

🦋 Changeset detected

Latest commit: 96819f6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
@graphql-codegen/visitor-plugin-common	Patch
@graphql-codegen/typescript-operations	Patch
@graphql-codegen/typescript-document-nodes	Patch
@graphql-codegen/gql-tag-operations	Patch
@graphql-codegen/typescript-resolvers	Patch
@graphql-codegen/typed-document-node	Patch
@graphql-codegen/typescript	Patch
@graphql-codegen/graphql-modules-preset	Patch
@graphql-codegen/client-preset	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[mvestergaard]

That's awesome! Thanks for figuring out a way to replicate it in a test @jdmoody

[n1ru4l]

Awesome, thank you ❤️

Can you please also generate a changeset? See #8664 (comment)

[jdmoody]

Can you please also generate a changeset? See #8664 (comment)

Updated! Thanks for all your work on such an excellent OS library.

[saihaj]

great work!

[saihaj]

https://github.com/dotansimha/graphql-code-generator/releases/tag/release-1669935201062