fix exception when generating boolean schemas (#5585)

Author: eiriktsarpalis

src/Libraries/Microsoft.Extensions.AI/Utilities/AIJsonUtilities.Schema.cs

@@ -138,8 +138,6 @@ public static JsonElement CreateJsonSchema(
         JsonSerializerOptions? serializerOptions = null,
         AIJsonSchemaCreateOptions? inferenceOptions = null)
     {
-        _ = Throw.IfNull(serializerOptions);
-
         serializerOptions ??= DefaultOptions;
         inferenceOptions ??= AIJsonSchemaCreateOptions.Default;
 
@@ -278,24 +276,24 @@ JsonNode TransformSchemaNode(JsonSchemaExporterContext ctx, JsonNode schema)
                 {
                     objSchema.Add(AdditionalPropertiesPropertyName, (JsonNode)false);
                 }
-            }
-
-            if (ctx.Path.IsEmpty)
-            {
-                // We are at the root-level schema node, update/append parameter-specific metadata
 
                 // Some consumers of the JSON schema, including Ollama as of v0.3.13, don't understand
                 // schemas with "type": [...], and only understand "type" being a single value.
                 // STJ represents .NET integer types as ["string", "integer"], which will then lead to an error.
-                if (TypeIsArrayContainingInteger(schema))
+                if (TypeIsArrayContainingInteger(objSchema))
                 {
                     // We don't want to emit any array for "type". In this case we know it contains "integer"
                     // so reduce the type to that alone, assuming it's the most specific type.
-                    // This makes schemas for Int32 (etc) work with Ollama
+                    // This makes schemas for Int32 (etc) work with Ollama.
                     JsonObject obj = ConvertSchemaToObject(ref schema);
                     obj[TypePropertyName] = "integer";
                     _ = obj.Remove(PatternPropertyName);
                 }
+            }
+
+            if (ctx.Path.IsEmpty)
+            {
+                // We are at the root-level schema node, update/append parameter-specific metadata
 
                 if (!string.IsNullOrWhiteSpace(key.Description))
                 {
@@ -354,7 +352,7 @@ static JsonObject ConvertSchemaToObject(ref JsonNode schema)
         }
     }
 
-    private static bool TypeIsArrayContainingInteger(JsonNode schema)
+    private static bool TypeIsArrayContainingInteger(JsonObject schema)
     {
         if (schema["type"] is JsonArray typeArray)
         {

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/AIJsonUtilitiesTests.cs

@@ -158,4 +158,11 @@ public enum MyEnumValue
         A = 1,
         B = 2
     }
+
+    [Fact]
+    public static void ResolveJsonSchema_CanBeBoolean()
+    {
+        JsonElement schema = AIJsonUtilities.CreateJsonSchema(typeof(object));
+        Assert.Equal(JsonValueKind.True, schema.ValueKind);
+    }
 }