model_validate returns None

[shadycuz]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

When using MyModel.model_validate, it returns None.

This works:

@classmethod
    def create_example(cls) -> str:
        example_data = {
            "StackName": "my-stack",
            "TemplateURL": "https://my-bucket.s3.amazonaws.com/my-template.yaml",
            "Parameters": {"TemplatesBucket": "FAKE"},
        }
        example_config = cls(**example_data)

        log.debug(f"Example config:\n{example_config}")

        model_data = example_config.model_dump(exclude={"TemplateURL", "TemplatePath", "ParameterGroups"})
        model_data["Parameters"] = {}
        return yaml.dump(model_data, indent=4, sort_keys=True)

This doesn't:

@classmethod
    def create_example(cls) -> str:
        example_data = {
            "StackName": "my-stack",
            "TemplateURL": "https://my-bucket.s3.amazonaws.com/my-template.yaml",
            "Parameters": {"TemplatesBucket": "FAKE"},
        }
        example_config = cls.model_validate(example_data)

        log.debug(f"Example config:\n{example_config}")

        model_data = example_config.model_dump(exclude={"TemplateURL", "TemplatePath", "ParameterGroups"})
        model_data["Parameters"] = {}
        return yaml.dump(model_data, indent=4, sort_keys=True)

output:

debug: Example config:
debug: None
Traceback (most recent call last):
  File "/workspaces/nvcloud/.venv/bin/nvcloud", line 6, in <module>
    sys.exit(cli())
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/workspaces/nvcloud/.venv/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/workspaces/nvcloud/nvcloud/config/commands.py", line 51, in create_example
    log.info(config_class.create_example())
  File "/workspaces/nvcloud/nvcloud/config/models.py", line 341, in create_example
    model_data = example_config.model_dump(exclude={"TemplateURL", "TemplatePath", "ParameterGroups"})
AttributeError: 'NoneType' object has no attribute 'model_dump'

Example Code

No response

Python, Pydantic & OS Version

pydantic version: 2.1.1
        pydantic-core version: 2.4.0
          pydantic-core build: profile=release pgo=true mimalloc=true
                 install path: /workspaces/nvcloud/.venv/lib/python3.10/site-packages/pydantic
               python version: 3.10.12 (main, Jun  7 2023, 19:32:10) [GCC 10.2.1 20210110]
                     platform: Linux-5.15.90.1-microsoft-standard-WSL2-x86_64-with-glibc2.31
     optional deps. installed: ['typing-extensions']

Selected Assignee: @adriangb

Edit: My use case for model_validate() is I need to provide context for some of my field validators.

[Viicos]

Could you please provide more info/a MRE? I can't reproduce:

from pydantic import BaseModel

class ParametersModel(BaseModel):
    TemplatesBucket: str

class Model(BaseModel):
    StackName: str
    TemplateURL: str
    Parameters: ParametersModel

    @classmethod
    def create_example(cls) -> str:
        example_data = {
            "StackName": "my-stack",
            "TemplateURL": "https://my-bucket.s3.amazonaws.com/my-template.yaml",
            "Parameters": {"TemplatesBucket": "FAKE"},
        }
        example_config = cls.model_validate(example_data)
        print(example_config)

Model.create_example()
#> StackName='my-stack' TemplateURL='https://my-bucket.s3.amazonaws.com/my-template.yaml' Parameters=ParametersModel(TemplatesBucket='FAKE')

[Kludex]

Since we can't reproduce, I'll be closing the issue.

@shadycuz Please create a new issue with a reproducible example. 🙏

[TimChild]

I have also come across this behaviour. Unfortunately, the place I am seeing it is pretty complicated (lots of subclassing and mixins) so I can't easily give a MWE.
The problem has only appeared after a pretty major refactor that I didn't think would affect my pydantic schema too much, but obviously I changed something...

Anyway, just commenting to show that this is not a totally isolated case, but I'm also pretty confident that I've done something stupid somewhere so I don't think it's worth re-opening...

Edit:
Confirmed, I did something stupid... Accidentally forgot to return self from a model_validator...
See #9334 for example