There are even newer versions available (4.*), but I had found a bug
in it which prevented it from working with mypy-protobuf. For now,
sticking to just 3.20.1
Mypy will (correctly, I think) start flagging `type[type[Any]]` as an illegal annotation when mypy 0.980 comes out. Let's fix it now, before it comes out.
When a `connection_factory` argument is provided to psycopg2's `connect` function, the function's return type now matches that of the factory output class. However, if `cursor_factory` is set and has a non-`None` value and/or `connection_factory` is not set or is `None`, the return type is simply `connection`, as before.
* Return types for psycopg2 dict connections
DB connection and cursor methods that deal with `dict`-style results now indicate the expected return types as implemented.
* Return types for psycopg2 namedtuple connections
DB connection and cursor methods that deal with `namedtuple` results now indicate the expected return types as implemented.
* Use ABC iterator
As required by flake8, the `Iterator` referenced in psycopg2's `extras` module has been switched to the `collections.abc.Iterator[T]` variant.
* Fix base psycopg2 cursor iter return type
The previous return type of `Self` is wrong; `cursor`'s `__iter__` method returns an `Iterator`.
* Correct return type for cursor iter and next methods
The previous attempt to fix the return type of `cursor`'s (and subclasses) `__iter__` method was misguided; they should indeed return `Self`. It's the `__next__` methods that had to be updated to return the correct record/row instance type.
* Comprehensive overloads for psycopg2 extra connections
Provides full method signatures for the `cursor` methods of the `DictConnection`, `RealDictConnection` and `NamedTupleConnection` types. Notably this includes a default value for `cursor_factory` in each case, while preserving the option to override the parameter manually.
* Have mypy ignore incompatible psycopg2 return types
The return types of the `fetch*` and `__next__` methods of `DictCursor`, `RealDictCursor` and `NamedTupleCursor` are incompatible with the base `cursor` class's corresponding methods' return types. However, this does accurately reflect reality, so ignore the mypy errors in those cases.
* Use ABC callable for psycopg2 extras module
As required by flake8, the `Callable` referenced in psycopg2's `extras` module has been switched to the `Callable` variant.
* Remove superfluous psycopg2 member overrides
Several members in the `DictCursorBase` type definition were entirely unnecessary, so they have been removed. In addition, adds a type to the `size` param of the `cursor`'s `fetchmany` method.
