Custom Config Model for runnables.

[rever1and]

I've tried to use custom config spec to config custom runnables for a while.

In the most of the time, all works like a charm. I implement a runnable have custom config_spec like this:

ConfigurableFieldSpec(                                                                    
            id="arg1",                                                                      
            annotation=Optional[int],                                                             
            name="Arg one",                                                                    
            description="some configurable thing for this runnable.",                                                           
            default=None,                                                                         
            is_shared=True,                                                                        
)

Even more, I can annotate a BaseModel.

class Arg2(BaseModel):
    param: Optional[float]

...
ConfigurableFieldSpec(                                                                    
            id="arg2",                                                                      
            annotation=Optional[Arg2],                                                             
            name="Arg two",                                                                    
            description="some configurable collection for this runnable.",                                                           
            default=None,                                                                         
            is_shared=True,                                                                        
)

For most of the part everything works well, but I've found two problem.

Problem 1

The first is in the swagger docs, the default value is like this

 "config": {
    "configurable": {
      "arg2": {
        "param": 0,
      },
...

It does not respect arg2's default value in the spec, which should be none. and it will set a dict or zero for this situation.(Where arg2 is a basemodel, so a dict with all field set, and param to be 0)

Problem2

The second problem is langserve is different with runnable's direct invoke(and other endopint too) with optional config. When I run

runnable.invoke(input, {"configurable": {}})

The config set for runnable will not contain these optional fields.

but when I tried to invoke via langserve's api handler, I noticed it will be serialized with all optional fields with None value.

I will got config like this

{"configurable": {"arg1": None, "arg2": {"param": None }}}

For the second problem

My quick solve for this is to add exclude_unset=True here.

langserve/langserve/api_handler.py

Line 142 in 594527e

config_dicts.append(config.dict())

Question

I'm not sure if the way to use runnable config the right way.

Any advice on custom runnable config, and related problem?