[MEAI] Custom ChatOptions.AdditionalProperties ignored on deserialization.

[arthuridea]

Description

Custom additional properties is ignored when mapping to OpenAI.Chat.ChatCompletionOptions models.
The static method ToOpenAIOptions in OpenAIModelMapper.ChatCompletion.cs leaves custom properties unhandled.
It works fine in OpenAI .NET library using IJsonModel and JsonElement for serialization.

Reproduction Steps

// passing "web_search" for some LLMs...
var optionJson = """
    {
        "model": "some LLM model id",
        "stream": true,
        "web_search": {
            "enabled": true,
            "enable_trace": true,
            "enable_citation": false
        },
        "stream_options": {
            "include_usage": true
        },
        "messages": [
            {
                "role": "user",
                "content": "some user prompts...."
            }
        ]
    }
"""u8.ToArray();
///////////// case OpenAI serialization senario:
ChatCompletionOptions openAIChatCompletionOptions = new();
var binaryData = BinaryData.FromBytes(optionJson);
openAIChatCompletionOptions = ((IJsonModel<ChatCompletionOptions>)openAIChatCompletionOptions).Create(binaryData, ModelReaderWriterOptions.Json);
// We can find additional serialized data successfully deserialized

///////////// case MEAI serialization senario:
using MemoryStream optionStream = new(optionJson);
var chatRequest = await OpenAISerializationHelpers.DeserializeChatCompletionRequestAsync(optionStream);
var options = chatRequest.Options;
// Properties missing after deserialization.

Expected behavior

Custom properties will also be deserialzed.

Actual behavior

Custom properties unhandled.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[stephentoub]

This support is being removed as part of #6094 / #6138. It's relying on private reflection into the OpenAI library and is not something we can actually make stable. The missing properties here are a good example of how it's deficient, since the OpenAI library it wraps doesn't expose the ability to achieve this.

[arthuridea]

This support is being removed as part of #6094 / #6138. It's relying on private reflection into the OpenAI library and is not something we can actually make stable. The missing properties here are a good example of how it's deficient, since the OpenAI library it wraps doesn't expose the ability to achieve this.

Will the whole ChatClient(or other clients) implementation or only mapping extension methods be removed?
Should I open an issue in OpenAI.NET repo,rquesting if any public methods will be provided, or in some day,we can use a rquest & response mapping delegations here?............which will make codes ugly :( @stephentoub

[stephentoub]

The IChatClient implementation (and IEmbeddingGenerator impl) is planned to move into the OpenAI library itself.

[jeffhandley]

Noting this issue will need to be reviewed during that effort.