(fix, csharp): map<string, unknown> values are nullable (#4153)

generators/csharp/codegen/src/context/CsharpTypeMapper.ts

@@ -63,11 +63,15 @@ export class CsharpTypeMapper {
         switch (container.type) {
             case "list":
                 return Type.list(this.convert({ reference: container.list, unboxOptionals: true }));
-            case "map":
-                return Type.map(
-                    this.convert({ reference: container.keyType }),
-                    this.convert({ reference: container.valueType })
-                );
+            case "map": {
+                const key = this.convert({ reference: container.keyType });
+                const value = this.convert({ reference: container.valueType });
+                if (value.internalType.type === "object") {
+                    // object map values should be nullable.
+                    return Type.map(key, csharp.Type.optional(value));
+                }
+                return Type.map(key, value);
+            }
             case "set":
                 return Type.set(this.convert({ reference: container.set, unboxOptionals: true }));
             case "optional":

generators/csharp/sdk/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+- Improvement: `map<string, unknown>` types are now generated as `Dictionary<string, object?>` types so they
+  can support explicit `null` values. Note that this does _not_ affect every `unknown` type to be an `object?`
+  since it would otherwise alter its required/optional characteristics.
+
 ## [0.3.4 - 2024-07-30]
 
 - Improvement: Make datetime deserialization more lenient, and include milliseconds in datetime serialization.