Fix types, run typechecker in CI

[yorickvP]

I fell into a typing hole while setting up pyright-lsp. Nevertheless, I think these are good changes, mostly preventing some annoying crashes (ast_openapi_scha + bytes defaults, cpus being uncountable).

Fixes #1360

[technillogue]

hmm https://github.com/replicate/cog/blob/main/pyproject.toml#L50-L87

[yorickvP]

mypy finds largely the same errors. But lsp-pyright is really good. I can optionally add a tool.pyright section with some config.

extra stuff found by mypy (mostly untyped defs):

python/cog/command/ast_openapi_schema.py:9: error: Function "unparse" could always be true in boolean context  [truthy-function]
python/cog/command/ast_openapi_schema.py:12: error: Incompatible types in assignment (expression has type "Callable[[object], str]", variable has type "Callable[[AST], str]")  [assignment]
python/cog/types.py:264: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
python/cog/types.py:268: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
python/cog/server/http.py:77: error: Unsupported dynamic base class "schema.PredictionRequest.with_types"  [misc]
Found 5 errors in 3 files (checked 23 source files)

[erbridge]

Should we pick one of pyright or mypy and drop the other?

[technillogue]

would agree, would kinda lean towards sticking to mypy rather than making changes. pylsp-mypy exists though I assume it's slower

[yorickvP]

As a long-time mypy user, I like pyright more:

• can check untyped defs
• these things: https://github.com/microsoft/pyright/blob/main/docs/mypy-comparison.md
• has way more options to warn/error on things we weren't checking for

Notably pyright actually passes the pydantic stuff :)

[technillogue]

...I've had check-untyped-defs on the entire time I've used mypy. but I have to agree that this is fairly compelling even if the javascript stuff is weird.

[mattt]

@yorickvP Thanks for the nudge. I just gave Pyright a look, and found it to be an improvement over mypy. I'd be very happy for us to adopt it across the board. (To that end, I just opened this PR in our Python client)

[technillogue]

why?

[yorickvP]

tldr this allows typingchecking PredictionRequest usage by pyright (still not mypy, though)

[nickstenning]

Love it!

I'd like to request that if we go all in on pyright (which I fully support) then let's also get rid of all mypy references in the codebase (pyproject.toml/Makefile/etc.)

[nickstenning]

Modulo failing tests (I think we'll have to use "old" ways of defining union types for a while to support <3.10) this seems great, particularly the bit where we typecheck in CI!

[technillogue]

this PR probably shouldn't change async functionality