[ipjohnson]

Closes #627.

What changed

JsonSchemaWriter now writes JsonElement, JsonNode and JsonValue as {}, JsonObject as {"type":"object"} and JsonArray as {"type":"array","items":{}}. The types are matched by their System.Text.Json / System.Text.Json.Nodes namespace, so an application's own JsonNode is still reflected. ObjectRef skips indexers, so no schema has a this[] property. A nullable JsonObject or JsonArray gets null added to its type, which lowers to nullable: true at 3.0.0, and a nullable {} stays {}.

For the Refit criterion, scripts/verify-templates.sh copies scripts/probes/JsonDomController.cs into each code-first Refit row that uses the JSON serializer. It then builds the client project and checks that the DOM operations are in the generated client. This runs after the row's tests, because the scaffold's DocumentStatusTests fails on any operation it does not probe. The probe is removed afterwards.

The separate commit bumps MessagePack from 3.1.8 to 3.1.9 for GHSA-qhrr-8q5h-9q3h, which was published on 2026-10-15. Without it, NU1902 fails the Release CI build at restore, on main as well. The template's pin and the two doc pages that cite the version move with it.

How it was tested

JsonDomDocumentTests covers each of the five types as a property, a request body and a response. It runs the generated document through the export's lowering and YAML writer at 3.2.0, 3.1.0 and 3.0.0, and reads the YAML back with Microsoft.OpenApi to check it matches the JSON. It also checks that no component is written for the five types, JsonNodeOptions or JsonValueKind, that a user type named JsonNode is still reflected, and that an indexer is not a property. The suite fails 25 tests against the old writer.

scripts/verify-templates.sh kestrel:code:response:refit kestrel:code:throws:refit:nunit reports that the Refit client compiles over the DOM types on both rows. The overall run still fails on the Azure blob-trigger function row, because no storage emulator is listening on 127.0.0.1:10000 on this machine.

dotnet build Hardened.slnx --configuration Release -p:ContinuousIntegrationBuild=true has 0 warnings and 0 errors, dotnet test Hardened.slnx passes across all 80 test assemblies, and dotnet csharpier check . is clean. No golden fixture or tracked openapi/*.json changed.

🤖 Generated with Claude Code

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Agent Driver: session 2d7049bb, Task 2052ce41 (Describe System.Text.Json DOM types as free-form JSON in the OpenAPI document), item describe-system-text-json-dom-types-as-f. Open on your network