Typing support

[trexfeathers]

✨ Feature Request

typing — Support for type hints — Python 3.12.3 documentation

• Add MyPy to Iris' pre-commit hooks, initially non-strict and with as many exceptions as necessary
• Create a plan for progressively removing the MyPy exceptions, culminating in Iris being fully typed

Motivation

See #4272 and #4383

We know from @hdyson and @ESMValGroup/esmvaltool-developmentteam that the absence of typing in Iris causes problems when developing packages on top of Iris. I wanted to raise this issue as an explicit recognition that this is something we want to do, and to encourage 👍 voting to gauge people's appetite for this 'feature'.

[trexfeathers]

• Add MyPy to Iris' pre-commit hooks, initially non-strict and with as many exceptions as necessary

#5956