Input type with `Optional` field breaks Playground

[jmaness]

If a chain has an input type containing an optional field, the Playground page fails to load (blank page), and the following error is logged in the browser console:

index-400979f0.js:150 Uncaught Error: Unknown type: {"type":"null"}
    at VC (index-400979f0.js:150:3067)
    at Object.J6 [as uiSchema] (index-400979f0.js:150:3156)
    at bh (index-400979f0.js:148:40890)
    at index-400979f0.js:150:1495
    at Array.map (<anonymous>)
    at n0 (index-400979f0.js:150:1419)
    at index-400979f0.js:255:25928
    at z$ (index-400979f0.js:38:19538)
    at Uw (index-400979f0.js:40:3139)
    at p4 (index-400979f0.js:40:2351)

Example input type:

from pydantic import BaseModel
from typing import Optional


class Question(BaseModel):
    question: str
    datasource: Optional[str]

The generated input schema looks like:

{
  "properties": {
    "question": {
      "title": "Question",
      "type": "string"
    },
    "datasource": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "null"
        }
      ],
      "default": null,
      "title": "Datasource"
    }
  },
  "required": [
    "question"
  ],
  "title": "Question",
  "type": "object"
}

and the {"type":"null"} seems to cause an issue with jsonforms.

Should the generated input schema be the following instead?

{
  "properties": {
    "question": {
      "title": "Question",
      "type": "string"
    },
    "datasource": {
      "type": "string"
      "title": "Datasource"
    }
  },
  "required": [
    "question"
  ],
  "title": "Question",
  "type": "object"
}

[jmaness]

From reading through https://json-schema.org/understanding-json-schema/reference/object#required, it seems like the generated schema using anyOf and {"type":"null"} should be valid for optional properties, so perhaps this is a bug in jsonforms after all.

[tdakanalis]

Any fix or workaround on this?

[eyurtsev]

duplicate of: https://github.com/langchain-ai/langserve/issues/777