Cylc Validate failed to catch bad offset

[ukmo-ccbunney]

Description

An invalid isodatetime in the [[xtriggers]] section can get past cylc validate and cause a suite to fail.
I'm not sure if cylc validate should be expected to catch this typo, but I will raise it just in case:

    [[xtriggers]]
        L1_trigger = wall_clock(offset=PT755MH):PT30S  # <-- bad offset

I meant to type PT7H55M, but instead made a typo and wrote an offset of 755MH

My suite kept failing to start (it just launched immediately into a "stopped" state) and I couldn't figure out why.
I only realised my error when I checked the "Workflow log file"

2023-04-03T13:37:42Z ERROR - could not convert string to float: '755M'
    Traceback (most recent call last):
      File "/home/h03/fcm/cylc-8.1.2-2/lib/python3.9/site-packages/cylc/flow/cycling/iso8601.py", line 881, in interval_parse
        return _interval_parse(interval_string)
      File "/home/h03/fcm/cylc-8.1.2-2/lib/python3.9/site-packages/cylc/flow/cycling/iso8601.py", line 902, in _interval_parse
        return WorkflowSpecifics.interval_parser.parse(interval_string)
      File "/home/h03/fcm/cylc-8.1.2-2/lib/python3.9/site-packages/metomi/isodatetime/parsers.py", line 575, in parse
        value = float(value)
    ValueError: could not convert string to float: '755M'

Cylc validate usually shouts about these kind of isodatetime errors, but not in this case.

Reproducible Example

Add the above section into a flow.cylc and run as usual (I use cylc vip)

Expected Behaviour

Suite will validate and install ok, but will immediately show in UI as "stopped".
Check workflow log, you should see the error above.

[hjoliver]

Confirmed. Thanks for the bug report!

[hjoliver]

(Fix done, just testing it ...)

[ukmo-ccbunney]

Ace. Thanks for the speedy fix!