Implement an AppContext compatibility switch re-enabling reflection fallback in STJ source generators. #75694
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…allback in STJ source generators. (dotnet#75615) * Implement an AppContext compatibility switch re-enabling reflection fallback in sourcegen. * address feedback
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Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis Issue DetailsBackport of #75615 to release/7.0-rc2. Customer Impact.NET 7 introduced an intentional breaking change which removes silent fallback to reflection-based serialization in System.Text.Json source generators. Based on early feedback we have been receiving from customers and partner teams, it appears that quite a few users have (mostly accidentally) taken a dependency on the fallback behavior (see dotnet/aspnetcore#43894, dotnet/aspnetcore#43236 for a few examples). Even though a workaround for the breaking change has been documented, it still requires a code change which might not be possible in certain scenaria. This PR introduces an TestingAdded unit tests validating behavior with the compatibility switch enabled. RiskLow. Makes minimal adaptations to product code that only kicks in when the switch is enabled.
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src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/OptionsTests.cs
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Backport of #75615 to release/7.0-rc2.
Customer Impact
.NET 7 introduced an intentional breaking change which removes silent fallback to reflection-based serialization in System.Text.Json source generators. Based on early feedback we have been receiving from customers and partner teams, it appears that quite a few users have (mostly accidentally) taken a dependency on the fallback behavior (see dotnet/aspnetcore#43894, dotnet/aspnetcore#43236 for a few examples).
Even though a workaround for the breaking change has been documented, it still requires a code change which might not be possible in certain scenaria. This PR introduces an
AppContextcompatibility switch (namedSystem.Text.Json.Serialization.EnableSourceGenReflectionFallback) that brings back the reflection fallback logic for source generators.Testing
Added unit tests validating behavior with the compatibility switch enabled.
Risk
Low. Makes minimal adaptations to product code that only kicks in when the switch is enabled.