Elastic's Kibana API interaction with datamodel-code-generator not working

[AlejandroBaron]

Describe the bug

While trying to generate a pydantic code model with datamodel-codegen for Kibana's API, command didn't work. API is available here (https://www.elastic.co/docs/api/doc/kibana)

pydantic_core._pydantic_core.ValidationError: 1 validation error for JsonSchemaObject
required.2
  Input should be a valid string [type=string_type, input_value={'anyOf': ['to', 'cc', 'bcc']}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.10/v/string_type

Honestly I'm not able to figure out whether Kibana's OpenAPI export is malformed or is there a problem with the datamodel-code-generator, since the error is not very explicative, so this may not be a bug.

To Reproduce

Used commandline:

Local:

datamodel-codegen  --input ~/Downloads/kibana-openapi-source.json 

Remote

$ datamodel-codegen --url "https://www.elastic.co/docs/api/doc/kibana/v8.json"

Expected behavior Not getting an error

Version:

• OS: Ubuntu 24
• Python version: 3.10
• datamodel-code-generator version: 0.26.5

[HeroGamers]

These are the errors I currently get with the newest OpenAPI specifications provided by Elastic:

❯ uvx --from "datamodel-code-generator[http]" datamodel-codegen --url https://www.elastic.co/docs/api/doc/kibana.json --input-file-type openapi --disable-warnings --output model.py
Traceback (most recent call last):
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/datamodel_code_generator/__main__.py", line 473, in main
    generate(
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/datamodel_code_generator/__init__.py", line 480, in generate
    results = parser.parse()
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/datamodel_code_generator/parser/base.py", line 1178, in parse
    self.parse_raw()
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/datamodel_code_generator/parser/openapi.py", line 582, in parse_raw
    self.parse_raw_obj(
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/datamodel_code_generator/parser/jsonschema.py", line 1526, in parse_raw_obj
    self.parse_obj(name, self.SCHEMA_OBJECT_TYPE.parse_obj(raw), path)
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/pydantic/main.py", line 1222, in parse_obj
    return cls.model_validate(obj)
  File "/home/user/.cache/uv/archive-v0/UCkDNN2DAHUrkULTwK1Qb/lib/python3.8/site-packages/pydantic/main.py", line 627, in model_validate
    return cls.__pydantic_validator__.validate_python(
pydantic_core._pydantic_core.ValidationError: 1 validation error for JsonSchemaObject
required
  Input should be a valid list [type=list_type, input_value=None, input_type=NoneType]
    For further information visit https://errors.pydantic.dev/2.10/v/list_type

It is the same output with uvx --from "datamodel-code-generator[http]" datamodel-codegen --url https://www.elastic.co/docs/api/doc/kibana.yaml --input-file-type openapi --disable-warnings --output model.py.