Missing jsonargparse as dependency

[IsaiahHarvi]

Bug description

This is a 'object() takes no arguments' bug that is related to lightning not installing:
jsonargparse[signatures]>=4.27.7

What version are you seeing the problem on?

v2.5

Reproduced in studio

No response

How to reproduce the bug

Error messages and logs

  File "~/Projects/rf_ml/.venv/lib/python3.13/site-packages/lightning/pytorch/core/saving.py", line 91, in _load_from_checkpoint
    model = _load_state(cls, checkpoint, strict=strict, **kwargs)
  File "~/Projects/rf_ml/.venv/lib/python3.13/site-packages/lightning/pytorch/core/saving.py", line 165, in _load_state
    obj = instantiator(cls, _cls_kwargs) if instantiator else cls(**_cls_kwargs)
          ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
  File "~/Projects/rf_ml/.venv/lib/python3.13/site-packages/lightning/pytorch/cli.py", line 862, in instantiate_module
    parser = ArgumentParser(exit_on_error=False)
TypeError: object() takes no arguments
 

Environment

Current environment

* CUDA:
        - GPU:               None
        - available:         False
        - version:           None
* Lightning:
        - lightning:         2.5.1.post0
        - lightning-utilities: 0.14.3
        - pytorch-lightning: 2.5.1.post0
        - torch:             2.7.0
        - torchmetrics:      1.7.2
        - torchsig:          0.4.1
        - torchvision:       0.22.0
* Packages:
        - accessible-pygments: 0.0.5
        - adversarial-robustness-toolbox: 1.20.0
        - aiohappyeyeballs:  2.6.1
        - aiohttp:           3.12.4
        - aiosignal:         1.3.2
        - alabaster:         1.0.0
        - annotated-types:   0.7.0
        - anyio:             4.9.0
        - asttokens:         3.0.0
        - attrs:             25.3.0
        - autocommand:       2.2.2
        - babel:             2.17.0
        - backports.tarfile: 1.2.0
        - beautifulsoup4:    4.12.3
        - brotli:            1.1.0
        - build:             1.2.2.post1
        - certifi:           2025.4.26
        - cffi:              1.17.1
        - charset-normalizer: 3.4.2
        - click:             8.2.1
        - colorama:          0.4.6
        - contourpy:         1.3.2
        - cppy:              1.3.1
        - cycler:            0.12.1
        - cython:            3.0.12
        - decorator:         5.1.1
        - dnspython:         2.7.0
        - docker-pycreds:    0.4.0
        - docutils:          0.21.2
        - dpkt:              1.9.8
        - email-validator:   2.2.0
        - executing:         2.2.0
        - fastapi:           0.115.12
        - fastapi-cli:       0.0.7
        - filelock:          3.18.0
        - flake8:            7.1.1
        - fonttools:         4.58.0
        - frozenlist:        1.6.0
        - fsspec:            2025.5.1
        - gdown:             5.2.0
        - gitdb:             4.0.12
        - gitpython:         3.1.44
        - grpcio:            1.66.0
        - grpcio-tools:      1.66.0
        - h11:               0.16.0
        - h5py:              3.12.1
        - httpcore:          1.0.9
        - httptools:         0.6.4
        - httpx:             0.28.1
        - icecream:          2.1.4
        - id:                1.5.0
        - idna:              3.10
        - imagesize:         1.4.1
        - importlib-metadata: 8.5.0
        - inflect:           7.3.1
        - iniconfig:         2.1.0
        - installer:         0.7.0
        - ipdb:              0.13.13
        - ipython:           8.27.0
        - isort:             6.0.1
        - itsdangerous:      2.2.0
        - jaraco.classes:    3.4.0
        - jaraco.collections: 5.1.0
        - jaraco.context:    6.0.1
        - jaraco.functools:  4.1.0
        - jaraco.text:       3.12.1
        - jedi:              0.19.1
        - jinja2:            3.1.6
        - joblib:            1.4.2
        - keyring:           25.4.1
        - kiwisolver:        1.4.8
        - lightning:         2.5.1.post0
        - lightning-utilities: 0.14.3
        - linkify-it-py:     2.0.3
        - llvmlite:          0.43.0
        - lmdb:              1.5.1
        - lxml:              5.3.2
        - mako:              1.3.10
        - markdown-it-py:    3.0.0
        - markupsafe:        3.0.2
        - matplotlib:        3.10.3
        - matplotlib-inline: 0.1.7
        - mccabe:            0.7.0
        - mdit-py-plugins:   0.4.2
        - mdurl:             0.1.2
        - meson:             1.8.0
        - meson-python:      0.17.1
        - mock:              5.1.0
        - more-itertools:    10.5.0
        - mouseinfo:         0.1.3
        - mpmath:            1.3.0
        - multidict:         6.4.4
        - narwhals:          1.42.0
        - networkx:          3.4.2
        - nfstream:          6.5.4
        - nh3:               0.2.18
        - nids:              0.1.0
        - numba:             0.60.0
        - numpy:             2.2.6
        - oldest-supported-numpy: 0.1
        - olefile:           0.47
        - orjson:            3.10.18
        - packaging:         24.2
        - pandas:            2.2.3
        - parso:             0.8.4
        - pexpect:           4.9.0
        - piccolo-theme:     0.24.0
        - pillow:            11.2.1
        - pip:               25.1.1
        - pip-tools:         7.4.1
        - pkginfo:           1.10.0
        - platformdirs:      4.3.8
        - plotly:            6.1.2
        - pluggy:            1.6.0
        - ply:               3.11
        - prompt-toolkit:    3.0.48
        - propcache:         0.3.1
        - protobuf:          6.31.1
        - psutil:            7.0.0
        - psycopg2-binary:   2.9.10
        - ptyprocess:        0.7.0
        - pure-eval:         0.2.3
        - py-cpuinfo:        9.0.0
        - pyarrow:           19.0.1
        - pyautogui:         0.9.54
        - pybind11:          2.13.6
        - pycairo:           1.28.0
        - pycocotools:       2.0.8
        - pycodestyle:       2.12.1
        - pycparser:         2.22
        - pydantic:          2.11.5
        - pydantic-core:     2.33.2
        - pydantic-extra-types: 2.10.4
        - pydantic-settings: 2.9.1
        - pydata-sphinx-theme: 0.16.1
        - pyflakes:          3.2.0
        - pygetwindow:       0.0.9
        - pygments:          2.19.1
        - pygobject:         3.50.0
        - pymsgbox:          1.0.9
        - pyobjc-core:       10.3.1
        - pyobjc-framework-cocoa: 10.3.1
        - pyobjc-framework-quartz: 10.3.1
        - pypandoc:          1.13
        - pyparsing:         3.2.3
        - pyperclip:         1.9.0
        - pyproject-hooks:   1.2.0
        - pyproject-metadata: 0.9.1
        - pyqt-builder:      1.18.1
        - pyqt5:             5.15.11
        - pyqt5-sip:         12.17.0
        - pyrect:            0.2.0
        - pyscreeze:         1.0.1
        - pysocks:           1.7.1
        - pytest:            8.3.5
        - pytest-asyncio:    0.26.0
        - pytest-benchmark:  4.0.0
        - pytest-docker-pexpect: 0.9
        - pytest-mock:       3.14.0
        - python-dateutil:   2.9.0.post0
        - python-dotenv:     1.1.0
        - python-multipart:  0.0.20
        - pytorch-lightning: 2.5.1.post0
        - pytweening:        1.2.0
        - pytz:              2024.2
        - pywavelets:        1.8.0
        - pyyaml:            6.0.2
        - readme-renderer:   44.0
        - requests:          2.32.3
        - requests-toolbelt: 1.0.0
        - rf-ml:             0.1.0
        - rfc3986:           2.0.0
        - rich:              14.0.0
        - rich-toolkit:      0.14.6
        - roman-numerals-py: 3.1.0
        - rubicon-objc:      0.4.9
        - ruff:              0.11.11
        - scikit-learn:      1.6.0
        - scipy:             1.14.1
        - sentry-sdk:        2.29.1
        - setproctitle:      1.3.6
        - setuptools:        80.9.0
        - setuptools-scm:    8.3.0
        - shellingham:       1.5.4
        - sigkit:            0.0.3
        - sip:               6.10.0
        - six:               1.17.0
        - smmap:             5.0.2
        - sniffio:           1.3.1
        - snowballstemmer:   3.0.1
        - soupsieve:         2.6
        - sphinx:            8.2.3
        - sphinx-rtd-theme:  3.0.2
        - sphinxcontrib-applehelp: 2.0.0
        - sphinxcontrib-devhelp: 2.0.0
        - sphinxcontrib-htmlhelp: 2.1.0
        - sphinxcontrib-jquery: 4.1
        - sphinxcontrib-jsmath: 1.0.1
        - sphinxcontrib-qthelp: 2.0.0
        - sphinxcontrib-serializinghtml: 2.0.0
        - sqlalchemy:        2.0.41
        - stack-data:        0.6.3
        - starlette:         0.46.2
        - sympy:             1.14.0
        - tcai:              0.0.1
        - tcai-sdk:          0.1.0
        - textual:           0.82.0
        - threadpoolctl:     3.5.0
        - timm:              0.5.4
        - tomli:             2.2.1
        - torch:             2.7.0
        - torchmetrics:      1.7.2
        - torchsig:          0.4.1
        - torchvision:       0.22.0
        - tqdm:              4.67.1
        - traitlets:         5.14.3
        - twine:             6.1.0
        - typeguard:         4.3.0
        - typer:             0.15.4
        - typing-extensions: 4.13.2
        - typing-inspection: 0.4.1
        - tzdata:            2024.2
        - uc-micro-py:       1.0.3
        - ujson:             5.10.0
        - unicodedata2:      16.0.0
        - urllib3:           2.4.0
        - uv:                0.5.14
        - uvicorn:           0.34.2
        - uvloop:            0.21.0
        - wandb:             0.19.11
        - watchfiles:        1.0.5
        - wcwidth:           0.2.13
        - websockets:        15.0.1
        - wheel:             0.45.1
        - yarl:              1.20.0
        - zipp:              3.20.2
        - zopfli:            0.2.3.post1
* System:
        - OS:                Darwin
        - architecture:
                - 64bit
                -
        - processor:         arm
        - python:            3.11.12
        - release:           24.5.0
        - version:           Darwin Kernel Version 24.5.0: Tue Apr 22 19:52:00 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T6031

More info

No response

[deependujha]

Hi @IsaiahHarvi,

Thanks for raising the issue. Could you please share a minimal reproducible example on Lightning Studio so we can verify and debug it?

Regarding your PR to add jsonargparse as a base dependency, my understanding is that this is an intentional design decision to keep the base library lightweight and let users choose their preferred configuration parser (e.g., jsonargparse, omegaconf, or others).

If you’d like to use jsonargparse, you can install it separately or run:

uv pip install -r requirements/pytorch/extra.txt

Regards,
Deependu

[IsaiahHarvi]

If uv is the build system why would pyproject.toml not handle requirements in via dependency groups rather than requirements files? like the following example:

[project]
...
dependencies = [
    "lightning",
    "torchvision",
    "matplotlib",
    "numpy",
]

[dependency-groups]
dev = [
  "ruff>=0.12.7",
  "pytest",
]

train = [
  "torch",
  "lightning",
  "torchvision",
  "dvc",
  "dvclive",
  "jsonargparse[signatures]>=4.27.7",
  "onnx",
  "onnxscript",
]
...
```
Then installation is handled with
`uv sync` and various flags for specifying groups

[deependujha]

uv with dependency groups in pyproject.toml would be a cleaner approach.

Lightning is indeed in the process of migrating to uv, and there are already open issues tracking this. I believe @matsumotosan has been exploring it.

We’ll eventually move fully to uv and away from the separate requirements files, but for now we’re still in a transition phase.

[IsaiahHarvi]

Gotcha! Makes perfect sense. This is totally good to be closed as unplanned in my mind then.

[deependujha]

Thanks @IsaiahHarvi for taking the initiative to improve Pytorch-Lightning! 🙌
Looking forward to more contributions from you in the future.

Best,
Deependu