Support Windows

[ewjoachim]

• Add windows tests in the CI
• Check that signals work the same way
• Check that envvars work the same way
• Adjust documentation
• Find a windows maintainer

[ewjoachim]

Ping @aleksandr-shtaub

[aleksandr-shtaub]

I'll start from the easy ones.

Env vars

Works as expected.

CMD

rem Set value for a variable Name. Note: Should not contain any whitespaces around `=`.
> set Name=Value

rem Get value of variable `Name`.
> echo %Name%
Value

or

PowerShell

# Set value for a variable Name. Note: powershell have types, so use `""` for a string type.
> $Env:Name = "Value"  

# Get value of variable.
> echo $Env:Name
Value

Example

# test.py
import os
print(os.environ.get("Greeter"))

> $Env:Greeter = "Hello!"
> python -m test
Hello!

Paths

Unix: a/b/c
Win: a\\b\\c

Consider using Path.asPosix() instead of str(Path) when testing paths.

Signals

signal.SIGINT, signal.SIGTERM are supported (kind of) (1)

Subprocess

Different resolving of executable path (2)

We should use full paths or shell=True when we use subprocess.Popen().
Popen is in tests so there is nothing to worry about.

Popen.send_signal(signal.SIGINT) is not supported on win (3)

# subprocess.py
...
    def send_signal(self, sig):
        """Send a signal to the process."""
        # Don't signal a process that we know has already died.
        if self.returncode is not None:
            return
        if sig == signal.SIGTERM:
            self.terminate()
        elif sig == signal.CTRL_C_EVENT:
            os.kill(self.pid, signal.CTRL_C_EVENT)
        elif sig == signal.CTRL_BREAK_EVENT:
            os.kill(self.pid, signal.CTRL_BREAK_EVENT)
        else:
            raise ValueError("Unsupported signal: {}".format(sig))
...

Event Loop

add_signal_handler() and remove_signal_handler() aren't supported on win (4)

ProactorEventLoop and SelectorEventLoop (5,6,7,8)

We cant' use ProactorEventLoop because add_reader() and remove_reader() are used by aiopg.
Since Python 3.8 we need to change default policy explicitly like:

if os.platform == "win32":
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

Tests

Pytest-asyncio doesn't pickup policy stated in our code (9, 10)

We can rewrite fixture like this:

@pytest.fixture
def event_loop(request):
    """Rewrite event_loop fixture for pytest_asyncio."""
    if sys.platform == "win32":
        asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
    loop = asyncio.get_event_loop_policy().new_event_loop()
    yield loop
    loop.close()

---

TBC (if I find something else)

[aleksandr-shtaub]

Related:
#286
#444
#451

[ewjoachim]

Or even https://github.com/procrastinate-org/procrastinate/labels/Issue%20contains%3A%20Some%20Windows :)