fix: 6560 nullable required fields

[FGoessler]

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Description

This PR fixes an issue with JSOM schema based fields that are required and nullable at the same time. More details in issue.

Fixes #6560

Type of change

Please delete options that are not relevant.

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

Screenshots/Sandbox (if appropriate/relevant):

• Codesandbox for issue reproduction

Screenshot of failing test before fix:

Screenshot of passing test after fix:

How Has This Been Tested?

• Verified in a minimal local sample based on Codesandbox from issue
• Added unit test before fixing the issue

Test Environment:

• OS: MacOS 13.2
• NodeJS: v18.19.0

"@graphql-mesh/cli": "^0.88.6",
"@graphql-mesh/json-schema": "^0.98.0",
"graphql": "^16.8.1"

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• I have performed a self-review of my own code
• N.A. I have commented my code, particularly in hard-to-understand areas
• N.A. 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, and I have added a
  changeset using yarn changeset that bumps the version
• New and existing unit tests and linter rules pass locally with my changes
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[FGoessler]

These changes actually updated a bunch of snapshots tests. As far as I can see, these tests have been "false positives" before this fix. All those now optional fields should have been optional all the time.

The scope of this makes me wonder why this wasn't noticed earlier. 😅 😬

I also wonder whether this fix might be seen as a breaking change for consumers of GraphQL Mesh as a lot of types might now switch to optional. This not only changes the GraphQL schemas but also any generated TypeScript code based on it. That code then likely breaks compiling as additional non-null checks are required now. On the other hand, this might actually save some people from runtime issues as their Typescript compiler currently "falsely thinks" a field is always present but it actually can be missing. 🤔

[ardatan]

Thanks for the PR! But there were a few issues within this PR.
That code piece you removed is needed for complex cases with unions (allOf and anyOf). If we remove it, a JSON schema that has a prop required in parent but not in the child (anyOf or allOf) will be nonnullable which is not expected. Instead, I followed a different approach here;
#6563