Add type annotations everywhere, help needed

[asvetlov]

I'm working on adding type hints.
The hints are useless until their correctness is checked by mypy in strong mode.

The problem is: enabling the mode for the whole codebase generates too many errors.
Basically, it is the all-or-nothing situation.

The plan is: let's convert file by file.
To enable strong mode please uncomment mypy options from the settings file: https://github.com/aio-libs/aiohttp/blob/master/setup.cfg#L42-L48
Before submitting a Pull Request please make sure that uncommented config is not landed (revert settings back).

The job is trivial but requires updating too many source code lines, that's why I need a help from the community. Even small PRs are valuable.

[aio-libs-bot]

GitMate.io thinks possibly related issues are #3230 (iter_chunks type annotation wrong), #1181 (Provide MacOSX binary wheels. Help needed!), #3240 (Missing type annotations in pyi files), #2041 (File external links, help needed), and #2395 (Convert autodoc for multipart into written docs, help needed).

[asvetlov]

Supersedes #1749

[YuvalPruss]

@asvetlov If I want to contribute to this, which PR should I use?

[asvetlov]

aiohttp master branch as usual.
I quite don't understand the question about PR but assume you are asking for code branch to start work from.

[asvetlov]

Hint:
For MultiDict, CIMultiDict, Signal and FrozenList classes use forward declarations like "CIMultiDict[str]" or aiohttp.typedefs._CIMultiDict to avoid runtime errors.

[asvetlov]

tracing.py looks like an easy file to start.
One file per PR is a pretty good modularity for this meta-issue.

[asvetlov]

Finished

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new