Add special handling for array types in OpenAPI schema references.

src/OpenApi/src/Extensions/JsonTypeInfoExtensions.cs

@@ -114,6 +114,14 @@ internal static string GetSchemaReferenceId(this Type type, JsonSerializerOption
             return type.GetGenericArguments()[0].GetSchemaReferenceId(options);
         }
 
+        // Special handling for array types which use '[]' in their name that is not
+        // valid in OpenAPI schema keys (must match ^[a-zA-Z0-9\.\-_]+$).
+        if (type.IsArray)
+        {
+            var elementType = type.GetElementType()!;
+            return $"{elementType.GetSchemaReferenceId(options)}Array";
+        }
+
         // Special handling for generic types that are collections
         // Generic types become a concatenation of the generic type name and the type arguments
         if (type.IsGenericType)

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Extensions/JsonTypeInfoExtensionsTests.cs

@@ -81,6 +81,10 @@ public class Baz
         [typeof(Dictionary<string, List<string[]>>), null],
         [typeof(Dictionary<string, IEnumerable<string[]>>), null],
         [typeof(Foo<int>.Bar<string>.Baz), "BazOfintAndstring"],
+        [typeof(Ok<string[]>), "OkOfstringArray"],
+        [typeof(Ok<int[]>), "OkOfintArray"],
+        [typeof(Ok<Todo[]>), "OkOfTodoArray"],
+        [typeof(Ok<string[][]>), "OkOfstringArrayArray"],
     ];
 
     [Theory]