Python 3.6 support

[pawamoy]

Is your feature request related to a problem? Please describe.
I was able to install Python 3.7 with pyenv, then openapi-python-client with pipx, but now I see that the generated clients are compatible with Python >=3.7 as well, because of this instruction at least:

from __future__ import annotations

(see https://stackoverflow.com/questions/52889746/cant-import-annotations-from-future/52890129)

If I understand correctly, this annotations import is used to avoid putting quotes around forward references (or avoid forward references themselves?) in models from_dict methods.

Describe the solution you'd like
Maybe openapi-python-client could provide a configuration option to tell what Python version is the target, and adapt its output to it. For Python 3.6, the from __future__ import annotations lines would be removed, and the from_dict methods of models would put quotes around their return type annotation.

Describe alternatives you've considered
I'm stuck with Python 3.6, at least for some time, so the only alternative I see is manually fixing the generated code, or writing a script to do it automatically 🙂

[pawamoy]

And here are two sed commands to do just that:

sed -i '/from __future__ import annotations/d' */models/*.py
sed -r -i 's/(def from_dict\(d: Dict\[str, Any\]\) -> )(.+):$/\1"\2":/' */models/*.py

Make sure to adapt */models/*.py to fit your directory structure.

[dbanty]

@pawamoy is that the only piece of the generated clients that isn't compatible with 3.6? If so then we can just change the style to use quotes instead of __future__ for now. I thought data classes were added in 3.7 and we make pretty extensive use of them I think.

[pawamoy]

dataclasses can be installed as a dependency from PyPI, so this is solvable for Python 3.6. As for your question, I'm not sure yet, I've only executed "import time" code.

[dbanty]

Okay so we should also add that dependency then for 3.6 support.

[dbanty]

@pawamoy 0.6.0-alpha.3 (building now) should work with Python 3.6 (both the CLI and the generated clients). Please give it a spin when you get a chance and see if I missed anything.

[pawamoy]

@dbanty that's great, thanks! I'll give it a try.

[dbanty]

I haven't heard any complaints yet, and CI is now running 3.6 on every commit- so I'm pretty confident releasing 0.6.0 will finish this up. I'm going to close this issue to mark progress on 0.6.0 milestone, but definitely open a new one if you encounter any issues.