Fix broken tests when running Config Schema Generator on .NET 9

[bart-vmware]

Description

Adapt the Config Schema Generator logic to deal with the breaking change in System.Text.Json v9, reported at dotnet/runtime#108790.

More specifically, this PR fixes the JsonNode handling inside Config Schema Generator to work with STJ v9. The generator project still targets .NET 8, but now references STJ v9 explicitly. Its test project now multi-targets against .NET 8 and 9.

Before this PR, the generator and its tests only ran on .NET 8 (referencing STJ v8), which is why there were no test failures.

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue:
  • No

/cc @eerhardt

Microsoft Reviewers: Open in CodeFlow

[joperezr]

Hello @bart-vmware, thanks for the contribution. This PR is currently set to target release/9.0-rc.1 which is no longer an active branch. Assuming you are okay with me re-targeting it against main ?

[bart-vmware]

@joperezr It probably won't work with main as-is, due to different TFMs and version numbers.

Can I update this PR to make it compatible with release/9.0 and target that? If it doesn't meet the bar (no worries), I'd rather wait until the final 9.0 release has shipped, and then update and retarget this PR.

[joperezr]

We are pretty locked down at this point for release/9.0 branch, so unfortunately wouldn't be able to take this into there. main is already a net9 TFM too, in fact main is our 9.1 branch now, so that would be the best place to target for your PR.

[joperezr]

Given the above, I'm retargeting this to go against main as the rc.1 branch is frozen anyway.

[eerhardt]

(Sorry for the late response. We were busy locking down for .NET Aspire 9.0, which will be released next week.)

[eerhardt]

Thanks for the PR here @bart-vmware. I've pushed some updates to make this ready for review. I took your suggestion of always using System.Text.Json 9.0.0 in the tool. This allows for much simpler code.

[bart-vmware]

@eerhardt Thanks for doing the updates, this is basically what I had in mind, so LGTM from me.

I've renamed ReplaceNode to ReplaceNodeWithKeyCasingChange for clarity, and fixed the broken test on .NET 9. I don't know why the explicit VersionOverride solves the problem, a multi-targeting glitch perhaps? Without it, the dependencies look like this:

[eiriktsarpalis]

Thanks

[eiriktsarpalis]

This workaround requires dual lookup if the key is missing, which suggests to me that a JsonObject.TryAddmethod similar to the one in dotnet/runtime#107947 might be necessary.

[bart-vmware]

Is this PR ready to be merged?

[eerhardt]

LGTM.

Thanks for the contribution @bart-vmware!