Re: [Configobj-develop] List handling in Validator

[Stefan P. <pa...@ik...>]

I see what the source of confusion might be. I am talking about values
after validation has been performed. So when I say that I assign
something and then the value is of type something I mean that it is
after validation. Maybe this clears up some issues?

On Mon, Jan 3, 2011 at 4:49 PM, Michael Foord <fuz...@vo...> wrote:
>> So when parsing the config file "1,2" is indeed interpreted as a list,
> No. 1,2 without quotes is a list. '1,2" with quotes is a string that happens
> to contain a comma.
My point is that I can do foo = 1,2  in a config file and it works
correctly, but if I do config["foo"] = '1,2' it does not work. I would
fully understand that "foo = '1,2'" and config["foo"] = "'1,2'" would
not work (Notice the quotes inside the quotes). I think it's confusing
that I can write one thing in a file, but not the exact same thing in
the source. In this case I assign 1,2 (n.b. without any quotes) in
both cases.

> Otherwise, as I indicated, string values that contain commas can be incorrectly split into lists.
Can you name a situation when splitting a string when something
expects a list would lead to unwanted results? Not splitting the
string, and instead assigning it directly _always_ leads to incorrect
results when a list is expected.

> However quoted strings can contain commas that don't represent lists
> which is why your suggestion of always splitting on commas is bad.
I'm certainly not suggesting that a string containing commas is
_always_ interpreted as a list. Only when a list is expected!
Maybe there is an error in my code, and it is always split, but that
is certainly not the intention.

> What would be the use case of force_int? I don't really understand your
> point here.
Assigning a string to something expecting an integer "just works".
Assigning a string to something expecting a list does not, instead
force_list is needed. Don't you see the inconsistent behavior? I don't
see why integers can be converted automatically (when needed) but
lists require a separate type for this to work.

>  If you want a list value then assign a list.
I could similarly say that if you want an int value then assign an
int. Yet integer conversion from a string happens automatically. Why
does not list conversion happen?

> Alternatively, it sounds like a reasonable feature request to ask for a
> method to parse a string using the ConfigObj syntax rules - so that you can
> use ConfigObj syntax for assigning strings.
I think that an assignment should work the same, regardless if it's in
a config file or in the source code.

Once again:
Assume the spec:
p = list()

Case 1, Conf file:
p = 1,2

Case 2, in source:
config['p'] = '1,2'

In both cases the right-hand side is: 1,2. The quotation marks in case
2 is there because of Python syntax. I am still assigning the value
1,2 without any quotes, just like in case 1.

Given the above spec, in both cases, after validation, I expect p to
be the list ['1','2']. Currently case 1 gives ['1','2'] while case 2
gives a validation error. I don't think it makes sense to get
different results given that the right-hand side is the same in both
cases.

-- 
Stefan Parviainen