[Bug] Instantiating objects and calling methods and functions CRASHES

🐛 Bug

https://hydra.cc/docs/next/patterns/objects#instantiating-objects-and-calling-methods-and-functions Following the 1.0rc instructions for object instantiation results in “ValueError: Input config does not have a cls field”, followed by “UnboundLocalError: local variable ‘cls’ referenced before assignment”.

To reproduce

** Minimal Code/Config snippet to reproduce ** pip install hydra-core --upgrade --pre

Basically copy pasted from the docs. All you have to do is make these files in the same dir, then run python main.py.

# config.yaml
myobject:
  target: models.Foo
  params:
    x: 10
    y: 20
    
myclassmethod:
  target: models.Foo.class_method
  params:
    z: 5

mystaticmethod:
  target: models.Foo.static_method
  params:
    z: 15

myfunction:
  target: models.bar
  params:
    z: 15

# models.py
from typing import Any
class Foo:
  def __init__(self, x: int, y: int) -> None:
    self.x = x
    self.y = y

  @classmethod
  def class_method(self, z: int) -> Any:
    return self(z, 10)

  @staticmethod
  def static_method(z: int) -> int:
    return z + 1

def bar(z: int) -> int:
  return z + 2

# main.py
import hydra
from models import Foo

@hydra.main(config_name="config.yaml")
def app(cfg):
  foo1: Foo = hydra.utils.call(cfg.myobject)  # Foo(10, 20)
  print(Foo)
  foo2: Foo = hydra.utils.call(cfg.myclassmethod)  # Foo(5, 10)
  print(Foo)
  ret1: int = hydra.utils.call(cfg.mystaticmethod)  # 16
  print(ret1)
  ret2: int = hydra.utils.call(cfg.myfunction)  # 17
  print(ret2)

if __name__ == "__main__":
    app()

** Stack trace/error message **

Traceback (most recent call last):
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/utils.py", line 29, in call
    cls = _get_cls_name(config)
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/_internal/utils.py", line 489, in _get_cls_name
    raise ValueError("Input config does not have a cls field")
ValueError: Input config does not have a cls field

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "main.py", line 16, in <module>
    app()
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/main.py", line 37, in decorated_main
    strict=strict,
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/_internal/utils.py", line 253, in run_hydra
    lambda: hydra.run(
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/_internal/utils.py", line 185, in run_and_report
    func()
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/_internal/utils.py", line 256, in <lambda>
    overrides=args.overrides,
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/_internal/hydra.py", line 114, in run
    job_subdir_key=None,
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/core/utils.py", line 107, in run_job
    ret.return_value = task_function(task_cfg)
  File "main.py", line 6, in app
    foo1: Foo = hydra.utils.call(cfg.myobject)  # Foo(10, 20)
  File "/home/andrew/.miniconda3/envs/pt/lib/python3.7/site-packages/hydra/utils.py", line 37, in call
    log.error(f"Error instantiating '{cls}' : {e}")
UnboundLocalError: local variable 'cls' referenced before assignment

Expected Behavior

The code in the docs for Hydra’s class instantiation should work.

System information

• Hydra Version : 1.0rc
• Python version : 3.7
• Virtual environment type and version : None
• Operating system : Manjaro Linux

Additional context

Add any other context about the problem here.

[omry]

Pass it up as in a HydraException.

[shagunsodhani]

Yup. As misspelled cls will cause the problem. The right thing is to catch the ValueError: Input config does not have a cls field and pass it up. Will fix it with #737