In autocompletion.py, the should_list_installed boolean expression was
flipped to workaround upstream black bug:
https://github.com/psf/black/issues/1629
The bug makes black fail to stabilize formatting when the list isn't the
last piece of the expression.
The typing module has been available since Python 3.5. Guarding the
import has been unnecessary since dropping Python 2.
Some guards remain to either:
- Avoid circular imports
- Importing objects that are also guarded by typing.TYPE_CHECKING
- Avoid mypy_extensions dependency
The stdlib module has been available since Python 3.5 and the
TYPE_CHECKING constant has been available since 3.5.2.
By using stdlib, this removes the need for pip to maintain its own
Python 2 typing compatibility shim.
When running autocomplete after any command-line option with unspecified
'metavar' attribute, a traceback for an 'AttributeError' would be
displayed. This is fixed for first checking if 'metavar' was defined.
Fixes#5751
