Fix C# JSON request and response handling for integer collections

[Copilot]

Nested JSON requests containing int16, uint16, uint32, or uint64 collections can throw NotSupportedException; top-level array and record responses can return empty collections despite populated payloads.

• Request serialization: Use non-generic IEnumerable for recursive collection handling, preserving dictionary-as-object and byte-array-as-base64 precedence.
• Response deserialization: Extend conversion gates and numeric getters for short, ushort, uint, and ulong, including nullable elements.
• Regression coverage: Exercise generated sync/async request and response paths across all four types, including range boundaries, empty collections, null entries, invalid values, and dictionary/byte-array compatibility.

• Fixes [Bug]: Complete JSON request/response support for newly mapped C# integer collections #12284

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npm i https://pkg.pr.new/@typespec/http-client-csharp@12295

commit: 16f0c0e

[Copilot]

🟢 Approval recommended

Static review found no blocking issues in the targeted fixes and regression coverage; tests were not executed.

0 open findings

What changed in this PR

Closes the two JSON collection gaps from #12284 in the C# client emitter, following the integer mappings added by #12283.

Changes:

• Supports recursive serialization of value-type collections while preserving dictionary and byte-array handling.
• Adds response conversion for short, ushort, uint, ulong, and nullable variants.
• Adds generated clients and sync/async regression coverage for boundaries, empty collections, nulls, and invalid values.

Paths below are relative to packages/http-client-csharp/generator/.

File	Description
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt64Collections.RestClient.cs	Adds UInt64 request construction.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt64Collections.cs	Adds UInt64 collection operations.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt32Collections.RestClient.cs	Adds UInt32 request construction.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt32Collections.cs	Adds UInt32 collection operations.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt16Collections.RestClient.cs	Adds UInt16 request construction.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​UInt16Collections.cs	Adds UInt16 collection operations.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​SampleTypeSpecClient.cs	Exposes the four collection sub-clients.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​Internal/​ModelSerializationExtensions.cs	Updates generated recursive collection serialization.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​Int16Collections.RestClient.cs	Adds Int16 request construction.
TestProjects/​Local/​Sample-TypeSpec/​src/​Generated/​Int16Collections.cs	Adds Int16 collection operations.
TestProjects/​Local/​Sample-TypeSpec/​Sample-TypeSpec.tsp	Defines reusable integer collection scenarios.
TestProjects/​Local.Tests/​ModelSerializationExtensionsTests.cs	Checks dictionary, byte-array, and unsupported-element behavior.
TestProjects/​Local.Tests/​IntegerCollectionTests.cs	Exercises generated sync/async collection paths.
Microsoft.TypeSpec.Generator.ClientModel/​test/​Providers/​Definitions/​TestData/​ModelSerializationExtensionsDefinitionTests/​ValidateWriteObjectValueXmlIncludesFileBinaryContentCase.cs	Updates the XML-enabled helper baseline.
Microsoft.TypeSpec.Generator.ClientModel/​test/​Providers/​Definitions/​TestData/​ModelSerializationExtensionsDefinitionTests/​ValidateWriteObjectValueIncludesFileBinaryContentCase.cs	Updates the JSON helper baseline.
Microsoft.TypeSpec.Generator.ClientModel/​src/​Providers/​ScmMethodProviderCollection.cs	Extends integer response conversion gates and getters.
Microsoft.TypeSpec.Generator.ClientModel/​src/​Providers/​ModelSerializationExtensionsDefinition.cs	Generates non-generic enumerable handling.

🧠 Review effort: Balanced

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[Jorge Rangel (jorgerangel-msft)]

Copilot are we addressing both

1. Nested integer collections fail to serialize in JSON request bodies
2. Top-level integer collection and record responses deserialize as empty collections

? I'd like to also ensure we have unit tests to cover both areas

[Copilot]

Copilot are we addressing both

1. Nested integer collections fail to serialize in JSON request bodies
2. Top-level integer collection and record responses deserialize as empty collections...

Yes—both fixes are included. Added explicit request coverage in db18db6:

1. NestedIntegerCollectionRequestsUseBinaryContentHelpers checks generated sync/async request methods against TestData. NestedIntegerRequestBodiesSerialize adds 64 cases covering nested arrays and records of arrays for all four types, including lists, boundaries, null elements, and empty collections. All 64 fail with NotSupportedException using the pre-fix helper and pass with the fix.
2. IntegerCollectionResponsesUseUtf8JsonReader checks TestData baselines for top-level arrays/records across all four types, including nullable elements and sync/async methods. These were also verified to fail against the pre-fix generator.

All 2,463 ClientModel and 796 Local unit tests pass. Sample-TypeSpec fixtures remain unchanged.

[Copilot]

🟡 Changes recommended

Required runtime response tests remain missing; source baselines do not verify returned values or invalid-payload behavior.

1 open finding

• Add runtime deserialization coverage for integer collection responses · New

🧠 Review effort: Balanced

[Jorge Rangel (jorgerangel-msft)]

Copilot there's test failures we need to address and possibly regenerate the test libraries:

Total execution time: 00:09:37.67
Code generation is completed.
Checking for differences in generated code...
> git -c core.safecrlf=false diff --ignore-space-at-eol --exit-code -- ":(exclude)/mnt/vss/_work/1/s/packages/http-client-csharp/package.json" ":(exclude)/mnt/vss/_work/1/s/packages/http-client-csharp/package-lock.json"
diff --git a/packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Internal/ModelSerializationExtensions.cs b/packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Internal/ModelSerializationExtensions.cs
index a21365f48..3d4ae845a 100644
--- a/packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Internal/ModelSerializationExtensions.cs
+++ b/packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Internal/ModelSerializationExtensions.cs
@@ -321,7 +321,7 @@ namespace SampleTypeSpec
                     break;
                 case IEnumerable objectEnumerable:
                     writer.WriteStartArray();
-                    foreach (object item in objectEnumerable)
+                    foreach (var item in objectEnumerable)
                     {
                         writer.WriteObjectValue<object>(item, options);
                     }

[Copilot]

Copilot there's test failures we need to address and possibly regenerate the test libraries:

Synchronized the checked-in Local Sample-TypeSpec generated source to the generator’s foreach (var item ...) output in commit $(git rev-parse --short HEAD). The focused ClientModel tests (10) and Local tests (796) pass. The repository generation script could not rebuild the emitter here because @types/node is unavailable, so I applied the exact generated one-line diff.

[Copilot]

🔵 Needs a closer look

Required runtime tests through generated synchronous and asynchronous client request methods are still missing.

0 open findings

1 resolved since last review

• Add runtime deserialization coverage for integer collection responses

Previously missed (1)

In code that hasn't changed since last review

Test generated client request bodies for integer array operations

packages/​http-client-csharp/​generator/​TestProjects/​Local.Tests/​ModelSerializationExtensionsTests.cs:75

These tests call BinaryContentHelper with object-typed collections, and ScmMethodProviderCollectionTests.cs:2535–2558 only compares generated source, so neither verifies requests sent by generated sync/async client methods as required by #12284. Add tests calling generated nested-array and record-of-arrays operations for short, ushort, uint, and ulong, and assert the captured JSON bodies; switching between WriteTo and WriteToAsync here does not exercise those client methods.

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Response regressions compare generated source but do not execute generated clients and assert returned collection values as required by #12284.

1 open issue

• Verify generated response collection values and invalid inputs · New

_{Review effort: Balanced}