Make typing_extensions optional.

[c-bata]

Motivation

An alternative approach for #3980 to fix typing_extensions related issues.

Description of the changes

Check the typing.TYPE_CHECKING flag to check if type checking is enabled.

[codecov-commenter]

Codecov Report

Merging #3990 (396d762) into master (79f0329) will decrease coverage by 0.10%.
The diff coverage is 58.82%.

@@            Coverage Diff             @@
##           master    #3990      +/-   ##
==========================================
- Coverage   90.60%   90.50%   -0.11%     
==========================================
  Files         167      167              
  Lines       13111    13119       +8     
==========================================
- Hits        11879    11873       -6     
- Misses       1232     1246      +14     

Impacted Files	Coverage Δ
optuna/_convert_positional_args.py	89.28% <57.14%> (-10.72%)	⬇️
optuna/integration/pytorch_distributed.py	35.91% <57.14%> (-0.96%)	⬇️
optuna/_deprecated.py	94.28% <60.00%> (-5.72%)	⬇️
optuna/_experimental.py	92.45% <60.00%> (-7.55%)	⬇️

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[contramundum53]

I removed typing_extension and the tests ran successfully.
(Except for importance_tests and sampler_tests/test_samplers.py which use torch internally.)
LGTM.

[toshihikoyanase]

I don't think this is a blocker of this PR, but I found that typing-extensions was installed along with SQLAlchemy in Python 3.6 and 3.7. Without typing-extensions, users cannot import optuna due to the following errors.

$ python -c "import optuna"
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/importlib_metadata/_compat.py", line 9, in <module>
    from typing import Protocol
ImportError: cannot import name 'Protocol'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
...
  File "/proj/optuna/storages/_rdb/storage.py", line 27, in <module>
    from optuna.storages._rdb.models import TrialValueModel
  File "/proj/optuna/storages/_rdb/models.py", line 8, in <module>
    from sqlalchemy import asc
...
  File "/usr/local/lib/python3.6/site-packages/importlib_metadata/_meta.py", line 1, in <module>
    from ._compat import Protocol
  File "/usr/local/lib/python3.6/site-packages/importlib_metadata/_compat.py", line 11, in <module>
    from typing_extensions import Protocol  # type: ignore
ModuleNotFoundError: No module named 'typing_extensions'

The reproducible code is as follows:

1. Launch a container of the specific version of the python docker image.

$  git clone https://github.com/c-bata/optuna.git -b make-typing-extensions-optional
$ cd optuna
$ MINOR_VERSION=7 
$ docker run -it --rm -v $(pwd):/proj --workdir=/proj python:3.$MINOR_VERSION bash

2. Execute following commands

$ python --version
$ pip install -U pip
$ pip install .
$ python -c "import optuna"
$ pip freeze | grep typing
$ pip uninstall typing-extensions
$ python -c "import optuna"

The results are shown in the following table:

Python	typing-extensions	import optuna without typing-extensions
3.6.15	4.1.1	ImportError
3.7.12	4.3.0	ImportError
3.8.12	not installed	✔️
3.9.13	not installed	✔️
3.10.4	not installed	✔️

[toshihikoyanase]

(e.g. We cannot install tensorflow=2.5.0 with typing_extensions>=3.10.0.0).

With this PR, we can use tensorflow=2.5.0 and optuna, if we install tensorflow in prior to optuna.

root@fee7c0b17cda:/proj# pip freeze | grep tensorflow
tensorflow==2.5.0
tensorflow-estimator==2.5.0
root@fee7c0b17cda:/proj# pip freeze | grep typing
typing-extensions==3.7.4.3
root@fee7c0b17cda:/proj# python -c "import optuna"

[c-bata]

@toshihikoyanase Thank you for your review!
It looks like the issue of SQLAlchemy. I checked that typing-extensions are specified in install_requires for each version of SQLAlchemy. The results are as follows:

• In the latest release SQLAlchemy v1.4.41, typing_extensions is not listed in install_requires.
  • https://github.com/sqlalchemy/sqlalchemy/blob/rel_1_4_41/setup.cfg
• In the main branch, typing_extensions>=4.1.0 is listed in install_requires. So this issue will be resolved at the next release.
  • https://github.com/sqlalchemy/sqlalchemy/blob/main/setup.cfg#L40

Even though Optuna's RDBStorage users may bump into this problem, I don't think typing-extensions should be included in Optuna's install_requires. What do you think?

[toshihikoyanase]

Even though Optuna's RDBStorage users may bump into this problem, I don't think typing-extensions should be included in Optuna's install_requires. What do you think?

I agree with you. With this PR, the typing_extensions will not be a dependency of Optuna, so I don't think we have to keep it in the requirements. In addition, users have workaround to use libraries that requires older version of typing_extensions, so the original issue seems to be resolved. I'll approve this PR after checking the behavior of code suggestion features of IDE (i.e., VS Code).

[toshihikoyanase]

In the latest release SQLAlchemy v1.4.41, typing_extensions is not listed in install_requires.
https://github.com/sqlalchemy/sqlalchemy/blob/rel_1_4_41/setup.cfg

Actually, it indirectly depends on typing_extensions via importlib-metadata.

• https://github.com/sqlalchemy/sqlalchemy/blob/ac9a74ac0d60f5e95d9dbbce7f804f532bef2bea/setup.cfg#L42-L43
• https://github.com/python/importlib_metadata/blob/53e42d6d70bd2068cd5bf0d351df89aa3cc0af31/setup.cfg#L21

And also, PrettyTable required by cliff also depends on importlib-metadata. So, some other libraries might depends on typing_extensions and it may be difficult to remove typing_extensions from the indirect dependencies.

[toshihikoyanase]

In my environment, the code suggestion of VS Code worked as expected. I cannot understand why, but it worked even if typing_extensions was not installed in the virtual environment.

The code suggestion for the deprecated method (i.e., trial.suggest_uniform) is shown as follows:

The code suggestion for a method with @convert_positional_args (i.e., optuna.create_study) is shown as follows:

The code suggestion for an experimental method (i.e., optuna.storages.RetryFailedTrialCallback) is shown as follows:

[toshihikoyanase]

LGTM.