[Blazor] Removes problematic system.text.json switches

[javiercn]

The fix in dotnet/runtime#102876 was not enough to resolve the problem so we've decided to not set the problematic feature flag to enable p5 to ship

/cc @lewing

Customer Impact

Any project using using these runtime feature flags will not work with the latest System.Text.Json

• Customer reported
• Found internally

[Select one or both of the boxes. Describe how this issue impacts customers, citing the expected and actual behaviors and scope of the issue. If customer-reported, provide the issue number.]

Regression

• Yes
• No

[If yes, specify when the regression was introduced. Provide the PR or commit if known.]

Testing

[How was the fix verified? How was the issue missed previously? What tests were added?]

Risk

[High/Medium/Low. Justify the indication by mentioning how risks were measured and addressed.]

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

[dotnet-policy-service]

Thanks for your PR, @javiercn.
To learn about the PR process and branching schedule of this repo, please take a look at the SDK PR Guide.

[sebastienros]

Should it also get rid of these occurrences?

sdk/src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj

Line 27 in f848676

<NullabilityInfoContextSupport>false</NullabilityInfoContextSupport>

sdk/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets

Line 579 in f848676

<RuntimeHostConfigurationOption Include="System.Reflection.NullabilityInfoContext.IsSupported"

[baronfel]

@sebastienros IMO no - those are to test SDK functionality where the SDK faithfully translates MSBuild flags that users set in their own projects into runtiemconfig.json settings. Javier was specifically removing the use of these flags from blazor.

[ericstj]

cc @eiriktsarpalis @jozkee -- is there anything more we need to do in JSON to fix this better? I thought that @eiriktsarpalis's change dotnet/runtime#102876 would have made this unnecessary.

[lewing]

cc @eiriktsarpalis @jozkee -- is there anything more we need to do in JSON to fix this better? I thought that @eiriktsarpalis's change dotnet/runtime#102876 would have made this unnecessary.

I think the problem is that that change tries to read the AppContext but the runtime feature switch directly substitutes the value https://github.com/dotnet/runtime/blob/d8c59a418e0857d2bdf71eea064cd6e55a093092/src/libraries/System.Private.CoreLib/src/System/Reflection/NullabilityInfoContext.cs#L25
It doesn't set it in the AppContext so the code https://github.com/dotnet/runtime/blob/d8c59a418e0857d2bdf71eea064cd6e55a093092/src/libraries/System.Private.CoreLib/src/System/Reflection/NullabilityInfoContext.cs#L25 doesn't get the correct value

[eiriktsarpalis]

I think the problem is that that change tries to read the AppContext but the runtime feature switch directly substitutes the value

Why is a substitution necessary in this case? Shouldn't AppContext.TryGetSwitch return the correct value regardless?

[sebastienros]

Adding this link as I think Larry wanted to use it

https://github.com/dotnet/runtime/blob/d8c59a418e0857d2bdf71eea064cd6e55a093092/src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Substitutions.Shared.xml#L37

[marcpopMSFT]

@javiercn is this needed for preview5? We're trying to get final changes in and a potential build.

[javiercn]

@marcpopMSFT we are having that discussion in chat right now. Let me loop you in.

[mkArtakMSFT]

Just discussed this in Tactics and approved for preview5.