[Bug] Variables.Add ignores validator and converter if help and default weren't passed

[dustdfg]

Look at following file:

import SCons
from SCons.Variables import *
env = Environment()

options = Variables()

def validator(key, val, env):
	raise SCons.Errors.UserError(f"validator: {key} {val}") from None

def converter(val):
	return False

options.Add("my_option", validator=validator, converter=converter)

options.Update(env)

print(options.GenerateHelpText(env))

print(options)

There is only option name passed aside converter and validator. Run `scons my_option="no". The code prints following:

scons: Reading SConscript files ...

my_option: 
    default: None
    actual: None

Variables(
  options=[
    ('my_option', ['my_option'], '', None, validator=<function validator at 0x7f09b02a5a80>, converter=<function converter at 0x7f09b02ef920>),
  ],
  args={},
  files=[],
  unknown={},
)

Here we see that it ignored validator and converter but if you will change the option from

- options.Add("my_option", validator=validator, converter=converter)
+ options.Add("my_option", "help", "default", validator=validator, converter=converter)

It will print as it should scons: *** validator: my_option False... The same is with converter...

Is it known? Should I convert it to issue?

[mwichmann]

Due to lack of a default, meaning default defaults to None, which means it isn't added to the initial dict which apparently messes up later processing. Looks like a bug, let me give it a bit more thought.

[dustdfg]

Ok. I've just tested and explicitly passed None as default and as a result it is still not expected behavior. If users case defaults to None explicitly (which is fairly possible) means that validator should work with None and if it can't it is a bug

[mwichmann]

This didn't turn out to be what I expected. Remove the star import from Variables - the publicly exposed (from an SConscript viewpoint) Variables is a function in the main part of the program (SCons.Script), which instantiates the Variables class with appropriate defaults. The star import overwrites that function with the symbol (class name) from SCons.Variables, so you get the wrong one, and in fact, the Variables package doesn't end up seeing your command-line argument.

[dustdfg]

Thanks!