Use source generator in JSON trimming tests

[ApparentlyPlus]

Fixes #53437.

The existing collection trimming tests now use the source generator, and I rewrote the remaining 16 SerializerEntryPoint apps (one per JsonSerializer overload) along with ObjectConvertersTest. Like the collection tests, they run with reflection disabled and on the Native AOT test leg.

These were removed in #53235, the same PR that deleted the DynamicallyAccessedMembers annotations they validated (#52268), so the source generated versions verify the overloads themselves instead. The same goes for Stack, Queue, Queue<T> and ConcurrentStack, restored here and supported by the source generator since #53393.

A nice consequence is that Hashtable no longer needs its browser-wasm skip. The generated ObjectCreator roots the constructor statically, and that is what was getting trimmed.

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[Copilot]

🟡 Changes recommended

Two critical serializer tests must flush Utf8JsonWriter before reading the stream.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR migrates JSON trimming tests to source-generated metadata for reflection-disabled and Native AOT coverage.

Changes:

• Adds generated serializer-overload and collection tests.
• Restores stack, queue, and object-converter coverage.
• Updates trimming-test wiring and assertion exit codes.

File summaries

File	Summary	Status
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/System.Text.Json.TrimmingTests.proj	Registers trimming test applications and execution settings.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/SerializeAsync.ToStream.TypedObject.cs	Tests generated async stream serialization for typed objects.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/SerializeAsync.ToStream.BoxedObject.cs	Tests generated async stream serialization for boxed objects.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.TypedObject.WithWriter.cs	Tests typed serialization through a writer; writer must be flushed before stream inspection.	Changes required: critical flush issue
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.TypedObject.cs	Tests typed string serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.BoxedObject.WithWriter.cs	Tests boxed serialization through a writer; writer must be flushed before stream inspection.	Changes required: critical flush issue
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.BoxedObject.cs	Tests boxed string serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToByteArray.TypedObject.cs	Tests typed byte-array serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToByteArray.BoxedObject.cs	Tests boxed byte-array serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/DeserializeAsync.FromStream.TypedObject.cs	Tests typed async stream deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/DeserializeAsync.FromStream.BoxedObject.cs	Tests boxed async stream deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromString.TypedObject.cs	Tests typed string deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromString.BoxedObject.cs	Tests boxed string deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromSpan.TypedObject.cs	Tests typed span deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromSpan.BoxedObject.cs	Tests boxed span deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromReader.TypedObject.cs	Tests typed reader deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Deserialize.FromReader.BoxedObject.cs	Tests boxed reader deserialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/ObjectConvertersTest.cs	Tests generated object converters.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Helper.cs	Provides shared generated collection-test helpers.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/StackOfT.cs	Covers generated generic stack serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/Stack.cs	Covers generated stack serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/QueueOfT.cs	Covers generated generic queue serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/Queue.cs	Covers generated queue serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ListOfT.cs	Covers generated list serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ISetOfT.cs	Covers generated set-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IReadOnlyDictionaryOfTKeyTValue.cs	Covers generated read-only dictionary serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IListOfT.cs	Covers generated generic list-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IList.cs	Covers generated list-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IEnumerableOfT.cs	Covers generated generic enumerable serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IEnumerable.cs	Covers generated enumerable serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IDictionaryOfTKeyTValue.cs	Covers generated generic dictionary-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/IDictionary.cs	Covers generated dictionary-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ICollectionOfT.cs	Covers generated generic collection-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ICollection.cs	Covers generated collection-interface serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/Hashtable.cs	Covers generated Hashtable serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/HashSetOfT.cs	Covers generated hash-set serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/DictionaryOfTKeyTValue.cs	Covers generated dictionary serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ConcurrentStack.cs	Covers generated concurrent-stack serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ConcurrentQueue.cs	Covers generated concurrent-queue serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/ConcurrentDictionary.cs	Covers generated concurrent-dictionary serialization.	Reviewed
src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/Collections/Array.cs	Covers generated array serialization.	Reviewed

Review details

Suppressed comments (2)

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.BoxedObject.WithWriter.cs:36

• The writer still owns the serialized POCO bytes when stream.ToArray() is called; the serializer does not flush the supplied Utf8JsonWriter. This makes the assertion observe an empty or incomplete stream. Flush the writer before reading the stream.
  src/libraries/System.Text.Json/tests/System.Text.Json.Tests/TrimmingTests/SerializerEntryPoint/Serialize.ToString.TypedObject.WithWriter.cs:36
• The writer still owns the serialized POCO bytes when stream.ToArray() is called; the serializer does not flush the supplied Utf8JsonWriter. This makes the assertion observe an empty or incomplete stream. Flush the writer before reading the stream.

• Files reviewed: 41/41 changed files
• Comments generated: 2
• Review effort level: Lite

[teo-tsirpanis]

Left some comments; they also apply to the other test files.

[Copilot]

🟡 Changes recommended

Restore the helper’s type-compatibility assertion and address the repeated exit-code issue.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 41/41 changed files
• Comments generated: 2
• Review effort level: Lite

[eiriktsarpalis]

Hi, an important thing to note about the reflection-based trimming tests is that they were introduced intentionally to support such use cases (most prominently in the case of blazor). Even though that arrangement has its problems, I wouldn't want to see coverage gone at the moment.

[teo-tsirpanis]

@eiriktsarpalis the problem is that these tests can break by seemingly unrelated changes, like in #132115. If there are scenarios where reflection-based serialization is guaranteed to be supported with trimming (the only thing I can imagine is POD types with primitive fields/properties and arrays thereof, after we root the assembly in question), maybe the trimming tests can be restricted down to these.