Add CxoTimeDescr descriptor and CxoTime.NOW sentinel

[taldcroft]

Description

This adds a descriptor that allows for dataclass attributes that are cast as CxoTime. This is most obvious looking at the test or docs.

This also adds a new class attribute CxoTime.NOW which is the new preferred way to specify the current time. Functions that used to be like

def func(stop=None):
    stop = CxoTime(stop)
    ...

should now be:

def func(stop=CxoTime.NOW):
    stop = CxoTime(stop)
    ...

While in the package I gave the cxotime.py module an __all__ attribute.

Requires

• Add TypedDescriptor class for typed descriptors ska_helpers#53
• Coerce TypedDescriptor default at instance creation  ska_helpers#54

Interface impacts

None

Testing

Unit tests

• Mac (new tests)

(masters) ➜  cxotime git:(cxotime-descr) git rev-parse HEAD                                                             
f0f3d24d17f318c54b483e644ead80142b7439e1
(masters) ➜  cxotime git:(cxotime-descr) pytest
===================================================== test session starts ======================================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/aldcroft/git, configfile: pytest.ini
plugins: timeout-2.1.0, anyio-3.6.2
collected 235 items                                                                                                            

cxotime/tests/test_cxotime.py .......................................................................................... [ 38%]
........................................................................................................................ [ 89%]
.........................                                                                                                [100%]

===================================================== 235 passed in 2.15s ======================================================

Independent check of unit tests by Jean

• Linux
• Mac (output below)

(ska3) flame:cxotime jean$ git rev-parse HEAD
f0f3d24d17f318c54b483e644ead80142b7439e1
(ska3) flame:cxotime jean$ python -c "import ska_helpers; print(ska_helpers.__version__);"
0.13.1.dev8+gd7f2e18
(ska3) flame:cxotime jean$ pytest
=================================================================================== test session starts ===================================================================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/jean/git/cxotime
plugins: timeout-2.1.0, anyio-3.6.2
collected 235 items                                                                                                                                                                       

cxotime/tests/test_cxotime.py ..................................................................................................................................................... [ 63%]
......................................................................................                                                                                              [100%]

=================================================================================== 235 passed in 2.50s ===================================================================================
(ska3) flame:cxotime jean$ 

Functional tests

No functional testing.

[jeanconn]

It is unclear to me if this was going to stay as-is or have small updates based on the Descr conversations yesterday.

[taldcroft]

@jeanconn - this is getting updated, but things are a little in flux now so stand by. I'm trying to introduce a NOW sentinel value but having some trouble with the descriptor stuff.

[taldcroft]

@jeanconn - this is now down to a simple subclass of TypedDescriptor and the main thing is to review the docs and tests. So it is ready for review again.

@javierggt - for this iteration there is no convenient way to set a default NOW. I played with a NOW sentinel but this got into a bit of a mess ¹ so I backed that out. Basically if you want NOW then it would be like:

@dataclass
class MyClass:
    stop: CxoTime | None = CxoTimeDescriptor()

obj = MyClass(stop=CxoTime.now())

Footnotes

1. Right now the TypedDescriptor coerces the default value to the type when the dataclass is created, NOT when the dataclass instance is created. I tried changing that in a way that seemed reasonable to me but this gave a very long an inscrutable error from within the dataclass decorator magic, so I gave up for now. ↩

[jeanconn]

The new NOW looks to be working but I've got failed tests with sot/ska_helpers#54 in PYTHONPATH .

================================================================================= short test summary info =================================================================================
FAILED cxotime/tests/test_cxotime.py::test_cxotime_descriptor_is_required - AssertionError: Regex pattern did not match.
FAILED cxotime/tests/test_cxotime.py::test_cxotime_descriptor_with_NOW - AssertionError: assert 0.0 == 0.5
============================================================================== 2 failed, 233 passed in 1.78s ==============================================================================

[taldcroft]

@jeanconn - I'm wondering if you made a mistake somehow? This is all looking good for me.

(masters) ➜  cxotime git:(cxotime-descr) git rev-parse HEAD                                                             
f0f3d24d17f318c54b483e644ead80142b7439e1
(masters) ➜  cxotime git:(cxotime-descr) pytest                                                                         
================================================== test session starts ==================================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/aldcroft/git, configfile: pytest.ini
plugins: timeout-2.1.0, anyio-3.6.2
collected 235 items                                                                                                     

cxotime/tests/test_cxotime.py ................................................................................... [ 35%]
................................................................................................................. [ 83%]
.......................................                                                                           [100%]

================================================== 235 passed in 2.22s ==================================================
(masters) ➜  cxotime git:(cxotime-descr) python -c 'import ska_helpers; print(ska_helpers.__version__)'
0.13.1.dev8+gd7f2e18
(masters) ➜  cxotime git:(cxotime-descr) ska3
(ska3) ➜  cxotime git:(cxotime-descr) env PYTHONPATH=/Users/aldcroft/git/ska_helpers pytest --pdb
===================================================== test session starts =====================================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/aldcroft/git, configfile: pytest.ini
plugins: timeout-2.1.0, anyio-3.6.2
collected 235 items                                                                                                           

cxotime/tests/test_cxotime.py ......................................................................................... [ 37%]
....................................................................................................................... [ 88%]
...........................                                                                                             [100%]

===================================================== 235 passed in 2.37s =====================================================

[jeanconn]

I did make a mistake and had a typo in PYTHONPATH so I wasn't getting the version of ska_helpers I thought. Thanks!

[javierggt]

typo: provided

[javierggt]

I would also say that it can be used in a class (not a dataclass) as long as the constructor initializes the attribute.

I checked that the following two worked as I expected.

class MyClass_1:
    time: CxoTime = CxoTimeDescriptor(default=CxoTime.NOW)
    def __init__(self, **kwargs):
        self.time = MyClass.time

class MyClass_2:
    time: CxoTime | None = CxoTimeDescriptor(default=None)
    def __init__(self, **kwargs):
        self.time = MyClass.time

Is there something else that one would need to do?

[taldcroft]

See sot/ska_helpers#54 (comment)