Add sourcegen support for required & init-only properties.

[eiriktsarpalis]

Updates the source generator to include support for required and init properties. This is done by piggybacking on the existing parameteric constructor infrastructure using property initializer syntax. For example, given the following type:

publicclassMyPoco{publicrequiredintX{get;set;}publicintY{get;init;}}

The source generator will now generate metadata treating X and Y as pseudo-constructor parameters and emit a delegate as follows:

ObjectWithParameterizedConstructorCreator=static(args)=>newMyPoco(){X=(int)args[0],Y=(int)args[1]}

Fix#58770.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Updates the source generator to include support for required and init properties. This is done by piggybacking on the existing parameteric constructor infrastructure using property initializer syntax. For example, given the following type:

publicclassMyPoco{publicrequiredintX{get;set;}publicintY{get;init;}}

The source generator will now generate metadata treating X and Y as pseudo-constructor parameters and emit a delegate as follows:

ObjectWithParameterizedConstructorCreator=static(args)=>newMyPoco(){X=(int)args[0],Y=(int)args[1]}

Fix #58770.

Author:	eiriktsarpalis
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

Removes any async void declarations per https://learn.microsoft.com/en-us/archive/msdn-magazine/2013/march/async-await-best-practices-in-asynchronous-programming#avoid-async-void

[eiriktsarpalis]

The test failures appear to be impacting release builds of wasm only. I'm able to reproduce the failures locally, and all seem related to an issue in which JsonSerializerOptions.ReferenceHandler configuration is being ignored. The error appears consistently and only occurs if the entire test suite is being run -- individual test runs are passing without issue. It also seems unrelated to the testing infrastructure changes in this PR, refactoring to a simple unit test that just calls into JsonSerializer is also failing. I'll keep investigating but at this point I'm running out of theories.

[layomia]

Sounds like the options configuration/instances might not be flowing through properly following the change to move the fast-path decision logic to the context (or just how the context/options are being instantiated). Since individual runs pass my mind also goes to threading issues with the options caching optimizations added in .NET 7. Not sure if these were considered but wanted to mention.

[eiriktsarpalis]

Since individual runs pass my mind also goes to threading issues with the options caching optimizations added in .NET 7. Not sure if these were considered but wanted to mention.

Had the same thought, but the errors keep popping up even with global caching disabled.

Something stranger than that is happening. I've been able to isolate the test failures to using the Roslyn4.4 target when running tests: #79890

Steps to reproduce (on WSL) :

./build.sh -os Browser -configuration Release && ./dotnet.sh build -t:Test src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Roslyn4.4.Tests.csproj \
-p:TargetOS=Browser -p:TargetArchitecture=wasm -p:Configuration=Release

[eiriktsarpalis]

PR blocked until #79943 can be addressed.

[eiriktsarpalis]

Given that #79943 has been fixed, rebasing changes to see if it resolves CI issues.