Good news everyone! We nearly have the full beam codebase passing in mypy. As we are now approaching the zero-error event horizon, I'd like to open up a discussion around enabling mypy in the PythonLint job. Every day or so a PR is merged that introduces some new mypy errors, so enabling this test is the only way I see to keep the annotations accurate and thus useful.
Developer fatigue is a real concern here, since static typing has a a steep learning curve, and there are still not a lot of experts to help consult on PRs. Here are some things that I hope will mitigate those concerns: - We have a lot of tying coverage, so that means plenty of examples of how to solve different types of problems - Running mypy only takes 10 seconds to complete (if you execute it outside of gradle / tox), and that will get better when we get to 0 errors. Also, running mypy in daemon mode should speed that up even more - I have a PR[1] to allow developers to easily (and optionally) setup yapf to run in a local git pre-commit hook; I'd like to do the same for mypy. - I will make myself and members of my team available to help out with typing questions in PRs Is there anyone else on the list who is knowledgable about python static typing who would like to volunteer to be flagged on typing questions? What else can we do to make this transition easier? [1] https://github.com/apache/beam/pull/10810 -chad
