Serialize timedelta objects in parseable form

[maddenp-cu]

Synopsis

This issue came up in practice. Given

a.yaml

start: !datetime 2025-01-01T00
stop: !datetime 2025-01-03T03
raw: !timedelta '{{ ((stop - start) * 0.8).total_seconds() / 3600 }}'

Current behavior:

$ uw config realize -i a.yaml | tee b.yaml
start: 2025-01-01T00:00:00
stop: 2025-01-03T03:00:00
raw: !timedelta '1 day, 16:48:00'

$ python
>>> from uwtools.api.config import get_yaml_config
>>> c = get_yaml_config("b.yaml")
>>> c["raw"]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/maddenp/git/uwtools/src/uwtools/config/support.py", line 204, in __repr__
    return "%s %s" % (self.tag, self.converted)
  File "/home/maddenp/git/uwtools/src/uwtools/config/support.py", line 226, in converted
    return dict(zip(UWYAMLConvert.TAGS, converters, strict=True))[self.tag](self.value)
  File "/home/maddenp/git/uwtools/src/uwtools/utils/time.py", line 28, in to_timedelta
    args = dict(zip(keys, map(float, value.split(":")), strict=False))
ValueError: could not convert string to float: '1 day, 16'

The problem is that the value '1 day, 16:48:00' that appears in b.yaml, which is the standard representation of the timedelta object given by calling str() on it, is not parseable by uwtools as a timedelta object.

New behavior:

$ uw config realize -i a.yaml | tee b.yaml
start: 2025-01-01T00:00:00
stop: 2025-01-03T03:00:00
raw: !timedelta '40:48:00'

$ python
>>> from uwtools.api.config import get_yaml_config
>>> c = get_yaml_config("b.yaml")
>>> c["raw"]
!timedelta 1 day, 16:48:00

It's fine for the timedelta object to be internally represented as 1 day, 16:48:00, but when it is serialized (dumped) to YAML, it needs to be in the format that uwtools supports so that it can be read in again later.

After this merges, I'd like to do a v2.12.2 bugfix release of this, too.

Type

• Bug fix (corrects a known issue)

Impact

• This is a non-breaking change (existing functionality continues to work as expected)

Checklist

• I have added myself and any co-authors to the PR's Assignees list.
• I have reviewed the documentation and have made any updates necessitated by this change.