JsonSerializer.SerializeToDocument results encapsulate buffers rented from the shared ArrayPool

[eiriktsarpalis]

Please do... and if I understood correctly that we're already dropping pool arrays as part of JsonDocument on success paths, please open an issue about that as well. Thanks.

Originally posted by @stephentoub in #73338 (comment)

Relevant code:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Write.Document.cs

Lines 117 to 123 in 4f835ae

	// For performance, share the same buffer across serialization and deserialization.
	// The PooledByteBufferWriter is cleared and returned when JsonDocument.Dispose() is called.
	PooledByteBufferWriter output = new(options.DefaultBufferSize);
	using Utf8JsonWriter writer = new(output, options.GetWriterOptions());
	WriteCore(writer, value, jsonTypeInfo);
	return JsonDocument.ParseRented(output, options.GetDocumentOptions());

Likely introduced by #57327, so this is not a .NET 7 regression.

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

---

Please do... and if I understood correctly that we're already dropping pool arrays as part of JsonDocument on success paths, please open an issue about that as well. Thanks.

Originally posted by @stephentoub in #73338 (comment)

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Write.Document.cs

Lines 117 to 123 in 4f835ae

	// For performance, share the same buffer across serialization and deserialization.
	// The PooledByteBufferWriter is cleared and returned when JsonDocument.Dispose() is called.
	PooledByteBufferWriter output = new(options.DefaultBufferSize);
	using Utf8JsonWriter writer = new(output, options.GetWriterOptions());
	WriteCore(writer, value, jsonTypeInfo);
	return JsonDocument.ParseRented(output, options.GetDocumentOptions());

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

[eiriktsarpalis]

Closing per feedback in https://github.com/dotnet/runtime/pull/73338/files/3604bcbe4f4cad74e2c430e1a45bb0a3180cbfc5#r938200249