build: switch to tomli for TOML v1 compliant parser

[FFY00]

Fixes #308

Signed-off-by: Filipe Laíns lains@riseup.net

[layday]

• Reading from a text stream is deprecated in tomli and will generate a warning which can be reinterpreted as an error in test suites.
• Please replace toml with tomli in tests/constraints.txt.
• Remove types-toml from setup.cfg.

[hukkin]

Suggested change

	try:
	import tomli as toml
	TOMLDecodeError: Type[Exception] = toml.TOMLDecodeError
	except ModuleNotFoundError: # pragma: no cover
	import toml as _toml
	toml = _toml # type: ignore
	TOMLDecodeError = _toml.TomlDecodeError
	try:
	from tomli import loads as toml_loads
	from tomli import TOMLDecodeError
	except ImportError: # pragma: no cover
	from toml import loads as toml_loads
	from toml import TomlDecodeError as TOMLDecodeError

Something like this plus changing these lines below

with open(spec_file, encoding='UTF-8') as f:
    spec = toml.load(f)

to

with open(spec_file, 'rb') as f:
        spec = toml_loads(f.read().decode())

will

1. avoid a deprecation warning in tomli
2. avoid making illegal line ending conversions when opening the file

[FFY00]

I generally prefer to keep full imports, but since we were already doing it for the error, we can have loads too.

[gaborbernat]

Here you want

patch.dict(sys.modules, {'tomli': None})

[FFY00]

Thanks, I did not know about it 😛

[FFY00]

Of course 🤦

[FFY00]

Nevermind, the teardown does not run after I yield or return the other fixture. Does anyone have any proposal on how to do this cleanly? pytest-mock is very much against giving us access over when the mock is removed, we would use unittest.mock directly.

[gaborbernat]

pytest-mock is very much against giving us access over when the mock is removed, we would use unittest.mock directly.

Yeah in this case I'd import and use that directly 🤔

[layday]

You are reloading the module before sys.modules is unpatched.

[layday]

Okay, I tried running the tests locally and I think I see what's going on. Try calling stopall on the mocker:

@pytest.fixture
def mock_tomli_not_available(mocker):
    loads = mocker.patch('tomli.loads')
    mocker.patch.dict(sys.modules, {'tomli': None})
    importlib.reload(build)
    try:
        yield
    finally:
        loads.assert_not_called()
        mocker.stopall()
        importlib.reload(build)

[FFY00]

That works too, and our use-case is simple enough that using stopall is fine.

[gaborbernat]

[FFY00]

😊