[Bug]: [http-server-csharp] Model with a `Record<unknown>[]` property generates C# that does not compile (missing `using System.Text.Json.Nodes;`)

[dtminnaar]

Describe the bug

Package: @typespec/http-server-csharp 0.58.0-alpha.30

Description

A model property typed as an array of Record<unknown> is emitted as JsonObject[], but the
generated model file does not include using System.Text.Json.Nodes;, so the generated project
fails to compile with CS0246: The type or namespace name 'JsonObject' could not be found.

A property typed as Record<unknown> directly (non-array) works correctly — the using
directive is emitted.

Reproduction

Repro

Playground link

import "@typespec/http";
using Http;

@service(#{ title: "Repro" })
namespace Repro;

model DatasetRow is Record<unknown>;

model Page {
  items: DatasetRow[]; // array of Record<unknown> -> JsonObject[]
}

@route("/rows")
interface Rows {
  @get list(): Page;
}

Actual output

generated/models/Page.cs (note: no System.Text.Json.Nodes):

using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Text.Json.Serialization;
using TypeSpec.Helpers;
using TypeSpec.Helpers.JsonConverters;

namespace Repro
{
    public partial class Page
    {
        [JsonPropertyName("items")]
        public required JsonObject[] Items { get; set; }  // CS0246
    }
}

Expected output

The same file with using System.Text.Json.Nodes; included, as already happens when a property
is typed Record<unknown> without the array.

Root cause

modelNeedsJsonNodes in src/components/models/model-helpers.ts decides whether a model file
gets the System.Text.Json.Nodes using. It checks whether a property's type is a
Record<unknown> model, but never unwraps array types, so Record<unknown>[] (an Array model
whose indexer value is the Record) is missed — while the type-expression emission for the same
property does produce JsonObject[].

Suggested fix

Unwrap array indexers before the record check (loop so nested arrays are covered):

/** Returns true if any property of the model uses Record<T> (mapped to JsonObject). */
export function modelNeedsJsonNodes($: Typekit, model: Model): boolean {
  for (const prop of model.properties.values()) {
    // Unwrap array types: Record<unknown>[] emits JsonObject[] and needs JsonNodes too
    let type = prop.type;
    while (type.kind === "Model" && $.array.is(type) && type.indexer?.value) {
      type = type.indexer.value;
    }
    if (type.kind === "Model" && $.record.is(type)) {
      // Only need JsonNodes for Record<unknown> (maps to JsonObject)
      const valueType = type.indexer?.value;
      if (valueType?.kind === "Intrinsic" && valueType.name === "unknown") return true;
    }
  }
  return false;
}

We are running this change as a patch-package patch against the compiled dist output and can
confirm it fixes the compilation error without affecting the existing non-array behavior.

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[github-actions]

🎯 Issue Triage

A model property typed as Record[] in @typespec/http-server-csharp generates JsonObject[] in C# without the required using System.Text.Json.Nodes; directive, causing a CS0246 compile error. The non-array Record case works correctly.

Category: Bug
Area: emitter:service:csharp

🔗 [Playground Reproduction]((typespec.io/redacted)

📋 Reproduction code

import "`@typespec/http`";
using Http;

`@service`(#{ title: "Repro" })
namespace Repro;

model DatasetRow is Record<unknown>;

model Page {
  items: DatasetRow[]; // array of Record -> JsonObject[]
}

`@route`("/rows")
interface Rows {
  `@get` list(): Page;
}

🔍 Analysis

• Affected file: src/components/models/model-helpers.ts in @typespec/http-server-csharp
• Root cause: modelNeedsJsonNodes checks whether a property's type is a Record model to decide if System.Text.Json.Nodes needs to be imported. It does not unwrap array types, so Record[] (an Array model whose indexer value is the Record) is missed — while the type-expression emitter does correctly produce JsonObject[].
• Fix: Unwrap array indexers before the record check in modelNeedsJsonNodes. The reporter has confirmed a patch-package fix resolves the compilation error.

📝 Suggested next steps

• In src/components/models/model-helpers.ts, update modelNeedsJsonNodes to unwrap array types before the $.record.is(type) check (see suggested fix in issue body)
• Add a unit test for a model property typed as Record[] / Record<unknown>[] to ensure the using System.Text.Json.Nodes; directive is generated
• Verify existing non-array Record behavior is unaffected

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