WIP: split the argparser logic to one more level

[tacaswell]

Currently we have two levels to the factory function to generate the CLI interface for caproto IOCs

• ioc_arg_parser -> all-in-one that gives you two dictionaries
• template_arg_parser -> gives you a parser and a function to extract those dictionaries

The first is useful for reducing boiler plate in servers, the second is useful if you need to inject some additional parameters to be extracted from the CLI.

This adds another layer which giver a ArgParser will add all of the standard flags which is useful when you have an existing CLI tool that you want to add caporto features to.

[wigging]

Can you provide a basic example of how these new features are implemented by a user? How would template_arg_parser be used for the example shown below?

from caproto.server import PVGroup, ioc_arg_parser, pvproperty, run

class SimpleIOC(PVGroup):
    A = pvproperty(value=1, doc="An integer")
    B = pvproperty(value=2.0, doc="A float")
    C = pvproperty(value=[1, 2, 3], doc="An array of integers (max length 3)")

if __name__ == "__main__":
    ioc_options, run_options = ioc_arg_parser(default_prefix="simple:", desc="Example")
    ioc = SimpleIOC(**ioc_options)
    run(ioc.pvdb, **run_options)

[wigging]

Adding a log level parameter to the run function would be useful for situations when not using the ioc_arg_parser approach.

from caproto.server import PVGroup, pvproperty, run

class SimpleIOC(PVGroup):
    A = pvproperty(value=1, doc="An integer")
    B = pvproperty(value=2.0, doc="A float")
    C = pvproperty(value=[1, 2, 3], doc="An array of integers (max length 3)")

if __name__ == "__main__":
    ioc = SimpleIOC(prefix="simple")
    run(ioc.pvdb, loglevel="info")

[tacaswell]

caproto/caproto/ioc_examples/chirp.py

Lines 52 to 74 in 46020e4

	if __name__ == "__main__":
	parser, split_args = template_arg_parser(
	default_prefix="chirp:",
	desc=textwrap.dedent(Chirp.__doc__),
	)
	def in_range(v):
	v = float(v)
	if not (0 < v < 1):
	raise argparse.ArgumentTypeError(f" {v} not in range [0, 1]")
	return v
	parser.add_argument(
	"--ramprate",
	help="The multiplicative factor to apply when chirping.",
	type=in_range,
	default=0.75,
	)
	args = parser.parse_args()
	ioc_options, run_options = split_args(args)
	ioc = Chirp(ramp_rate=args.ramprate, **ioc_options)
	run(ioc.pvdb, **run_options)

is one of a couple of existing examples of using template_arg_parser.

To use the new one it would be something like

...  # other code
parser = ...  # where ever you are getting it from now
split_function = extend_arg_parser(parser)  # mutates in place!
... # other code
args = parser.parse_args()
... # other code
ioc_options, run_options = split_args(args)
ioc = SimpleIOC(**ioc_options)
run(ioc.pvdb, **run_options)

[tacaswell]

I do not think we want to cross the details of setting up loggers and log levels with the business of actually running the IOC.